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Discussion Starter #1 (Edited)
Please note, the information in this tip sheet is not intended to take the place of a factory service manual or manufacturer’s instructions. Please verify all procedures and specifications outlined in the service and owner’s manuals for the year, make, and model you are working on. Be sure to follow all instructions for the equipment and tools you will be using provided by the manufacturer of that equipment. Read the Material Safety Data Sheets provided by the manufacturers of chemicals, chemical compounds, and mixtures, understand the risks, take appropriate safety measures, and wear personal protective equipment. Wear safety glasses, always adequately and redundantly support a vehicle, be careful around moving parts (fans, belts), and have a plan in case of fire.

The following are additional notes not found in the factory service manual to answer some questions that might come up, make the process go more smoothly, and increase preparation. Always verify thread sizes before using a tap or die by comparing to both an SAE and Metric thread gauge, and look up and verify part numbers as well. The factory service manual is still necessary and should be considered a must-have. It contains critical information on torque sequences, torque procedures, bolt coatings, and precautions.

It is significantly more difficult to do this job on a 3.8L six cylinder fourth generation F-body than most vehicles. Access to the engine is made more difficult because much of the engine is located underneath the cowl, and access to the rear of both cylinder heads to remove bracketry is very tight. There are many other sequencing problems and challenges as well. You should not consider doing this if you have limited experience, the car is needed for transportation this week, you do not have alternative transportation that is available for many weeks, you are working outdoors, your tool set can fit in a box that has a handle, or if you do not truly love your fourth gen F-body. Preferably you should have some sort of sentimental attachment to it, otherwise you will probably give up before it is done.

Your tool set should include 3/8 and ½ inch torque wrenches, a set of O-ring picks, fuel line spring lock connector tools, harmonic balancer removal tool if doing the front seal or pulling the front cover, reversible ratcheting wrenches (the kind with the flipper to reverse direction and a slight offset up on the box end, not the flat kind that you turn the wrench over to reverse direction). Some of the recurring sizes that you need a large selection of wrenches and sockets is 8mm, 13mm, and 15mm. Make sure you have a high quality 8mm or 5/16 socket in six-point, 3/8 drive for torquing bolts. The intake manifold bolts are very sensitive to rounding off if you are using lower quality tools.

This job is a combination of both Metric and SAE standard sizes. Threads can be either Metric or SAE. Generally speaking, stuff on the inside of the engine is standard, like the head bolts, rocker arm bolts, probably because this engine was designed in the early 1960’s. Stuff on the outside of the engine is more commonly metric (read the specific exceptions on the exhaust manifolds), including the accessory bolts and studs that are mounted on the front and rear of the cylinder heads such as the engine lift brackets and the left front EGR; which are 10mm x1.50 or 8mmx1.25. In addition to standard and deep well sockets in both standard and metric, you will need 3/8 drive swivel sockets. 13mm was used often and it especially helps to have a several different styles of wrenches to choose from. It helps to have ¼ and 3/8 drive extensions in 1” or 2” length as well, because there were several situations where a 3” long extension with short socket was too long, and a deep well socket was too short or awkward. 13mm deep 3/8 drive sockets in differing lengths (such as a mid-length) also help. Wobble extensions were used. I had a Creftsman 5/16 polished (long) combination wrench, and it rounded out and damaged an intake manifold bolt and wrench. I picked up a Mac 5/16 combination wrench, and there were no further problems.

Taps you will need include 7/16-14 (cylinder head bolt holes), 5/16-18 (rocker arm bolt holes, exhaust manifold stud holes, lower intake manifold bolt holes), 10mm x 1.50, a set of thread pitch gauges in both SAE and metric to make sure you are using the correct size before putting a tap in any hole.

At 172,000 miles on an engine with above average maintenance, the condition was as follows:
Coolant was leaking from the front of the engine. A pressure test made the problem worse, and finished off whatever was left of a weak gasket. It was done.

Ring ridge in cylinders: zero to none

Valve sealing: With the heads off the vehicle, I flipped them upside down, leveled them out, and poured solvent in the combustion chambers. The solvent held for over 5 minutes in all the combustion chambers, indicating decent sealing. I elected not to do a valve job. It is best to do a compression test prior to starting a complicated procedure, so you have some idea if it is not savable.

Valve stem seals: Somewhat hardened and in need of replacement. They were intact and not crumbling.

Head gaskets: Were actually ok on mine and could have gone longer. Having iron cylinder heads in this application certainly helped. Head bolts are torque to yield (stretch) and must be replaced if they are loosened. Fel-pro does sell them as a set. They do not come with the head gasket set and must be ordered separately. They come coated with a hardened red substance on the threads. They are installed just like they come out of the box; do not coat them with additional materials. The rocker arm bolts are also torque to yield (stretch). I could not find an aftermarket source for them and had to go to the former Pontiac dealer to order them. The part number was 24503515, there were 12 qty, and the cost was 2.30 each. The rocker arm bolts also come with the same hardened red substance on them, but the service manual says they should also be installed with the GM 12345493 or equivalent thread lock compound (High Temperature High Strength red Loctite). The freeze plugs were stainless steel and did not need touched. Aftermarket ones are zinc plated steel (inferior), or brass if you do some extra sourcing. Please read the notes below about accessing the valve cover gaskets if you are thinking of doing the head gaskets. Don’t forget to unhook the ground strap leading to the back of driver’s side cylinder head, at the firewall before pulling it.

Exhaust manifold studs are hybrid SAE/Metric with 5/16-18 going into the head itself, and 8mmx1.25 on the nut end. Restated, just to be clear, the studs have two different thread patterns; on one end is Standard SAE (American) threads and the other end is Metric for attaching any additional heat shielding. There are 6 studs per side for a total of 12 studs. 8 of the studs are the same (4 per side). Once you have the heat shield off, as you loosen the “nut” on the 8 similar studs, the whole stud unscrews. It turns out the structural nut is permanently affixed to the stud in that case. If you think that later on you will need to loosen the “nut” from the stud before reassembling, you will only ruin them. They do not come free. I tried heating the nut with a torch, and all I succeeding was in deforming the stud. I went to the dealer to order new ones and we realized that it is all one-piece; a fake stud. It is not easy to make out that kind of detail when they are rusty and crusty. Should any of the 8 not be serviceable the part number was 24502332 stud, and the cost was 3.48 each.

The other 4 exhaust manifold studs are real studs, and the 8mm x 1.25 nut on the end does come free; but again going into the cylinder head itself is 5/16-18. The purpose is to have the two real studs installed on the cylinder heads before beginning the assembly process. Then you put the exhaust manifold over these two studs, and just barely start the nuts to keep it from falling off. The exhaust manifold gasket can then be slid down from the top, because at the location of the two real studs the gasket is slotted. It makes the job slightly easier. When reassembling the engine note that the passenger side exhaust manifold should be loosely in place in the engine bay before putting the valve cover on, because it will be impossible to get past the air conditioning lines with the valve cover in place (do you really want to pull the a/c compressor bracket loose from the front of the engine, or try to remove the engine lift bracket again to remove the valve cover?!) The exhaust manifold flange to the y-pipe at the bottom utilizes long 8mm x 1.25 bolts. The two on the driver’s side manifold snapped off in the manifold when loosening, and I ended up drilling them out on the bench and installing Heli coils. The passenger side ones came free (I was using heat in both cases), and I used a tap and die to clean up the threads. The exhaust doughnut was serviceable in my application by Fel-Pro as 61018. When reinstalling, be careful not to overtorque the studs, they will break, and extraction can cause a person to have to start the whole job over, or use creative techniques to extract in the chassis, such as a left hand drill bit and specialized tools from the

Lower intake manifold gasket to cylinder head: In need of replacement, nearly breached or breached around coolant ports. This is a common problem on the 3800. These were plastic gaskets with embedded O-rings that deteriorate over time, especially in the presence of acidic cooling systems that have not had much maintenance.

The lower intake bolts use the GM 12345493 or equivalent thread lock compound. There appeared to be a mistake in the torque sequence on my 1998 GMP/98-F-3 Manual, in that #6 and #7 were pointing to the same bolt, and one of other bolts was not labeled. I made an obvious assumption.

Upper intake manifold to lower intake manifold gasket: Completely blown out at the front where the coolant passes through, a few inches under the thermostat. This was the primary culprit. It was a plastic gasket that had deteriorated and had become brittle. It was broken in many areas. Coolant was starting to get into the number 1 cylinder, because that runner was much cleaner than the rest.

1997 Pontiac Firebird 3.8L V6 Heater hose pipe (90 degree elbow): in poor condition, failing. It is a common coolant leakage problem on the 3.8L. This plugs into the front of the lower intake manifold and connects it to the tensioner assembly. The original is composite; aftermarket ones are aluminum (probably better). This is an O-ringed part. Note that you only need one on this particular 3.8l V6 variant. Some of the aftermarket kits, such as Help! Have two in the package. One is symmetrical, the other one is not. I just needed the symmetrical one. There are some sources that contain just the one that you need, though that do not get stocked locally in my case. It was a choice of paying 6 bucks for the one and waiting on it, or 11 bucks for the two and them having it in stock.

1997 Firebird 3.8l V6 timing chain notes: looked to be in good condition on my engine, but when I began removing it for replacement the plastic tensioner block broke in half at the pivot point from embrittlement. This can be purchased separately from the timing chain if you want to just replace the plastic piece.

If the front cover is off to access the timing chain, it is very easy to knock out the front oil seal from behind with a flat blade screwdriver and a hammer. If you have to pull it out from the front (not removing the front cover), it would be more difficult, but not impossible. Accessing the front cover area is time consuming and certainly added to the job. The gasket kits for the timing set do not include an abbreviated version of the oil pan gasket at the front. In the old days, you would cut the remnant of the oil pan gasket off flush with the block and replace just the portion at the front that is common to the timing cover. It is not included in the kit because the oil pan gasket is a metal core with an embedded O-ring. It would not be very possible to cut it off, so you just reuse it. I put a little RTV on the old oil pan gasket to feel better. The service manual said you should also loosen more of the oil pan bolts at the front of the engine, to let the oil pan drop down just a little to facilitate getting the front cover back in place.

Getting the front cover wiggled on is challenging, because you must also align the cogs from the oil pump at the crankshaft snout with the cogs in the lower timing gear that drive it. Then you have to clear the power steering pump pulley while aligning the front cover on the two dowel pins as well. Make sure you have a good mirror handy, to align the oil pump cogs. The oil pump can be rotated slightly to align it with the lower timing gear, by using an O-ring pick or a small screwdriver. It was difficult, when everything finally came together it was sudden and surprised me.

Per the manual, front cover bolts are installed with the equivalent of GM 12346004 sealant, which is Loctite PST 592 Thread Sealant, High Termperature, per the Loctite Automotive Aftermarket OEM Connection Brochure .pdf.

Front cover crankshaft seal: leaking

1997 Firebird 3.8L V6 valve cover gaskets: they are O-rings and were leaking. It is somewhat difficult to even do valve cover gaskets on this car. On the passenger side, the engine lift bracket at the firewall has to be removed to remove the valve cover, because the bottom rear valve cover bolt is completely obscured by it. Removing the engine lift bracket is very difficult. Before starting any of this job or ordering any parts, go out to your car and attempt to get to the bolts that hold it on. The bracket is held on by two short bolts in the rear of the cylinder head. The outboard bolt is the easier of the two. You might be able to hook onto it using a 13mm ratcheting reversible wrench with fine teeth. A flat ratcheting wrench that is not reversible will not work (the kind where you have to flip the wrench over to make it go in the opposite direction). The offset of the reversible kind is beneficial. The inboard bracket bolt has a stud projecting out from the end of the bolt. First the nut must be removed; it holds on the transmission dipstick tube tab. Then the bolt/stud is removed. It takes a 13mm open end wrench (the bolts are 10mm x1.50). It is most easily done with the intake manifold off. When reassembling, it is best to have the valve cover on and the engine lift bracket on before installing the upper intake, because it will be nearly impossible to get to later. You might note that all of this would be just a little easier if the wire harness could be moved slightly. There are two sheet metal loop clamps the bundle routes through on top of the bellhousing area at the back of the block that can be delatched. It is a standard S-hook, like a bra, with the clasp just being in the center of the width of the loop. The problem is that you really can’t get to them until the upper intake is off. It is easiest to work with them with both the upper and lower intake off. Once the lower intake is on, you will no longer be able to see what you are doing, but might be able to get them relatched. Once the upper intake is on, there is no chance in latching them back up. The driver’s side valve cover is a bit easier. Instead of having the engine lift bracket on the aft end of the engine, it is under the forward end of the engine. It also must be removed, but it is easy to get to. Two EGR related plumbing pipes must also be removed, the EGR, the ignition coil all must be removed. The coil bracket that is mounted to the rear of the cylinder head can actually stay on, including through upper and lower intake manifold replacement.

The upper manifold bolts are reusable if in good condition. The service manual did not talk about coating the upper intake manifold bolts with anything, so I installed mine dry. Many of the upper intake manifold bolts are wrenched with a 5/16 or 8mm. I would recommend having a 3/8 drive socket in that size in 6-point, as they are highly sensitive to stripping out around the corners. It should be a quality socket as well. When working on the upper intake manifold, look at the torque sequence diagram at the bolt in sequence number 7. It is at the rear of the upper intake manifold, and the upper intake plenum covers it up. There is just enough room to get a ratcheting 8mm or 5/16” wrench on it, again, the kind that is reversible and has a slight offset to it. The flat kind of ratcheting wrenches will not work well, you need that offset, and the teeth in the flat kind of ratcheting wrenches are too coarse. I ended up delivering the bolt to the hole with a very long pair of stork needle nose pliers. Then I took a pair of needle nose vise grips and clamped onto the open end of the ratcheting wrench. I was then able to deliver the ratcheting wrench clear back to the head of the bolt. Once the wrench had been delivered to the bolt head, there is just enough room to tighten it down.

1997 Firebird 3.8L V6, removing the fuel rail to remove the upper intake manifold: Removing the electrical connectors going to each injector: I used an O-ring pick to detach the turned down end of the wire clip from its cove, then the wire clip can be pulled from the base end. It is hard to get to the rear cylinder on the passenger side of the car. When I finally got it, the wire clip went flying and has yet to be found. The parts guy at the dealership could not find a separate listing for just the wire clip. I had to order a new replacement electrical connector, and that had the wire clip on it. The cost for just one of these connectors was $29.57, so be really careful in policing the clips up (the part number was 12085491). Incidentally, he said that GM will sell most any electrical connector on the harness separately, but that it takes calling a special phone number to find out what the part number is, because he did not have the breakdown available on his end. The cost is usually more than the one I ordered- think double or triple). To undo the fuel lines you will need the special tool for releasing the spring lock, I had that but they were still stuck on somewhat from age. I had to apply more force after the tool was engaged than I would have thought necessary. I thought maybe the tool was not suitable for this application, but no, they were just stuck on there real good. There are 4 nuts that hold the fuel rail assembly to the upper intake manifold. After loosening the four nuts, the fuel rail can then be wiggled out with the injectors still attached, as each injector only has a fat O-ring sealing it into the lower intake; they are not screwed into the manifold. The head gasket set came with 12 fuel injector O-rings, there is also one O-ring each at the top of each injector. It is easy to replace the top O-rings with the fuel rail assembly out of the car. There is another clip; a fatter sheet metal clip that holds them in that is easy to work with. These clips are available from RockAuto as ACDelco 17111800, but they are not the ones that go on the electrical connector. They are not needed unless lost.


2 Posts
Discussion Starter #2 (Edited)
1997 Firebird 3.8L V6 Heater hose replacement notes: The heater hoses; upper and lower, are serviced as a GM assembly that transitions from a molded hose that plugs into the tensioner with a special O-ringed fitting, then through hard lines that are mounted to the chassis frame beside the a/c compressor, then back to a molded hose near the firewall for the heater core. It would be extremely difficult to fabricate something to go in lieu of this assembly that snakes around all of the obstructions without chafing the hood. It is not available from the aftermarket (RockAuto-AutoZone-Reilley) that I am aware of. Buying a roll of heater hose at your parts store is not going to work. The assembly is still available from GM as part number 19257179 for $205 retail, but I found it online (ebay, Amazon) for $150 shipped. In case you are wondering, the bolt that holds it to the frame by the compressor is a T40 Torx, and a typical T40 3/8 socket with 3/8 ratchet will be too tall to get in there. I ended up breaking it loose with a long T40 Torx Allan style wrench, and then sourcing a T40 bit and a VIM or Titan HBR3 ratcheting bit wrench to get in there without removing the a/c compressor. To make it easier yet, I extended the ratcheting bit wrench with a length of 5/8 diameter steel tubing crushed slightly on one end (.083 wall thickness), but I had to sand the corners off the stationary end of the bit wrench slightly. I then plugged a 3/8” extension to make the wrench assembly long enough to get my fingers out from between the compressor and frame (when my fingers were in the crevice I could not move the bit wrench much at all). Access to the bolt can only be had from underneath (an alternative to this is to unbolt the compressor bracket from the engine with the a/c lines still attached to it- no need to discharge. There are 4 bolts holding the bracket to the front of the engine (3 qty are 13mm heads and one is a 10mm). There is also a stud that must be removed on the side of the block. First the 13mm nut, which holds on the engine ground lug. Then the stud itself (15mm; another fake stud with a permanently attached nut. The compressor can then be slid forward in the engine compartment as a means of alternative access).

At the firewall end, the constant tension hose clamps can be undone with really long needle nose stork pliers going nearly parallel with the horizon. Then I used the hog ring style stork pliers to wiggle the hoses free from the heater core. It may help to unplug the loop clamp for the electrical wire bundle from the top of the evaporator housing. The heater core is aluminum. At the belt tensioner (front) end things are a lot easier, with a twist to unlock fitting, and then it can be plucked out of the O-ring bore.

1997 Firebird 3.8L V6 Power steering pump and hose replacement notes: The power steering pump and all 3 hoses were spongey and leaking badly. The high pressure and low pressure hoses are carried by the aftermarket with no problems. However, the third hose is not. It is the big diameter one that leads from the bottom of the reservoir to the pipe that comes out of the bottom of the power steering pump. It is called the Reservoir Hose, GM has it, it was part number 26040373, and it is available on ebay.

If you are removing the front cover of the engine, leave the power steering pump off until after the front cover has been reinstalled. To get the pulley off the power steering pump, you will need a special tool. I used OTC 7185 with great satisfaction to remove it (I tend to prefer it over the SnapOn style because it is shorter; leaving extra room for an impact gun while in the chassis-not that I am advocating an impact gun being used with your precision tools). To reinstall I used a Performance Tool W87021.

I also made the mistake of dropping a ¼” extension and socket down the exhaust Y-pipe on the passenger side when installing the valve cover. It was retrieved with a 24” flexible magnetic pick-up tool on the third attempt. Flexible claws, a vacuum cleaner, giant welding magnet ran along the outside, and a few other schemes did not work. I should have had a sock covering the pipe. I should have also had the exhaust manifold in place and covering the hole anyway, because installing the manifold in the chassis once the valve cover is down is way harder (see other note).

Research all of the risks of chemicals and understand them prior to working with them. Wear appropriate Personal Protective equipment including gloves, goggles, and respirator. Much of the advice out there says do not use abrasives on gasket surfaces, as it can damage the sealing surface and the abrasives tend to get into the engine, possibly causing damage later. The problem was corrosion on the upper and lower intake manifolds where the gasket sprang a leak, and that took a special 3” very fine abrasive pad to remove it. It did a nice job, and consumed 1 for the lower intake and 1 on the upper intake.

I used them in the forward area of the thermostat port only. I also used a little bit of Ultra Gray RTV around the thermostat port area, because there was some pitting that could have exceeded the ability of the gasket to compensate for. Most premium gaskets are made for no additional coatings, and deviating from their instructions can be risky. The exception are the lower intake manifold to pan rail gaskets, which do take a dab of RTV at the intersection per both the service manual and the aftermarket gasket kit instructions.

If it sounds like I am trying to discourage someone from doing all of this, I am. There needs to be a really good reason to go through this much effort. If someone that is learning how to work on cars needs a really challenging problem to confirm their skill level (or to reconsider their career choice), then this will certainly push their boundaries. If there is a sentimental attachment to the car, then that could be a good reason as well. If the car is daily transportation and can just be resurrected with an upper intake gasket only, then maybe. Otherwise it is just a lot simpler and makes more sense to get something else that is easier to work on, for reliable daily transportation. The upper and lower intake gaskets, the cooked spark plug wires, the heater hose elbow, windshield wiper transmission issues, headlight flipper door motors are all endemic on these cars. Even if you are working for “free” on your own vehicle, your disposable time is worth something. The costs of labor as well as the cost of the parts must be weighed against how many more miles or years of satisfaction that can be expected from the car after the repairs are complete.

The far easier way to do all of this, would be to drop the engine/transmission/cradle out the bottom of the vehicle, and work on the assembly out of the chassis. It would require a two post lift. I imagine that is how dealerships performed the work. I would think that unbolting the brake calipers and tying them up out of the way so the hoses do not have to be removed, and doing the same with the compressor; sliding it, the bracket, and the a/c lines forward in the chassis, would allow the engine to be dropped out the bottom after disconnecting other wiring/systems/plumbing.

I would expect that attempting to negotiate the engine out of the top of the engine bay would be too hard, in part because there is no room for the boom to be directly above the engine. This would require building a very special fixture to attach the engine to the hoist chain, and clear the windshield/cowl (it would also probably require removing the intake manifold, and reinstalling the intake manifold in the chassis). In any case, pulling the engine out the top would more than likely require disconnecting the transmission, thereby eating up any time savings.

A word of advice I have read is that once the engine lift bracket on the passenger side has been removed, do not reinstall it. It prevents you from pulling the passenger side valve cover in the chassis without major disassembly work (removing the intake manifold to access the bolt that holds it on). The engine lift bracket both completely covers the rearmost valve cover bolt, and makes it impossible to remove the valve cover because the valve cover cannot clear the rocker arm assembly on the inside of the valve cover, as well as clearing the engine lift bracket itself on the outside since the engine lift bracket wraps around the valve cover.

If you get the idea, hey, I can make an access hole in the engine lift bracket itself so that one day I could get to the rear most valve cover bolt without having to remove the engine lift bracket; that will be a complete waste of time. You still will not be able to wiggle the valve cover from around the rocker arm and engine lift bracket. If you are still attached to your engine lift bracket for sentimental reasons or because you think that you might be able to pull the engine with it, guess again. There is no room for a chain to sling it anyway. It was really only more useful on the GM assembly line to facilitate moving the engines around the factory and into the cradle, with no chassis in the way.

Dropping the engine/cradle out the bottom could really make an unbearable job easy. Be safe with the lift, and plan in advance that dropping the assembly may significantly alter the weight and balance of the car on the lift, and thereby could cause the car to become unstable. Safety countermeasures would need to be planned for to prevent an accident. It would also be helpful to have an engineered dolly ready (with casters), to accept the cradle that you are dropping out the bottom.

I wish I would have done this all with a lift, but I do not have a lift. :BangHead:

But, if you are just doing the intake manifold gaskets, then by all means have at the job with the engine in the chassis.


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