2nd Gen Intake Manifold Gasket

Anybody out there got a step by step procedure for changing the IMG on the 2nd Gen 3.2? In reading the forums and there seem to be some varying opinions on how much needs to come apart, whether special tools are required, etc.

I have the Haynes manual but the procedures there often give instruction to refer to other procedures elsewhere in the manual. It's kind of hard (at least for me) to figure out exactly what to do.

I also have the Isuzu service manual but as far as I can tell the procedure there is only for the upper IMG (aka the Common Chamber). This is not where my leak is.

So does the EGR have to removed? How about the fuel injectors? Do they come out with the fuel rail? It looks like the throttle body must come off - is the gasket reusable?

Does the coolant have to be drained?

What other gaskets, o-rings, etc should I order so I'm not lacking for parts when it's going back together?

Does it make sense to replace the T-stat while the IMG is off?

Has anybody had this work done by a mechanic? How much did it cost?

I apologize for starting a whole new thread but I thought it might result in getting all the common knowledge around this repair into one place.

Thanks!!

I've just removed my intake on my 99. You shouldn't need to separate the upper and lower pieces. The only coolant that flows near there is through the throttle body and that can stay in place when unbolted from the intake. The fuel rail and injectors stayed with the intake and I left the throttle body on the engine still hooked up to the coolant lines. The EGR valve can stay on the intake if you have a wrench large enough to take the pipe loose. You'll need a 7/8" for the pipe nut. The tricky part is getting the fuel lines loose at the rear and there is a bracket that holds the fuel lines that bolts to the back of the intake than can be difficult to get out since you can't see them. They're a 10mm and there are two of them.

Another little thing you may not be aware of: The fuel injector connectors have blue locking tabs on the plugs. You have to slide those up before trying to disconnect the electrical connectors. You'll have to squeeze the me after pulling up the tab. They may be stuck also.

I'll post some pics that may clue you in on some stuff.

I would definitely change the thermostat while you're in there.

Here's a pic of the removed intake. You can see the four long bolts that need to be removed. They pass all the way through the upper and lower intake. There are 4 more nuts on each corner that attach to studs that stay on the engine.
http://www.bereanspokane.org/Temporary/intake.jpg

Here's a pic of the engine with intake removed. The tricky fuel line bracket is towards the back. It's sort of 'V' shaped near the EGR pipe.
http://www.bereanspokane.org/Temporary/engine.jpg


Here's a pic of a fuel injector connector with the locking tab in the up/unlocked position.
http://www.bereanspokane.org/Temporary/locking%20tab.jpg

Thanks for the pictures, Cat Fuzz. So is it the gasket visible in the second picture (and the one like it on the passenger side) that you are replacing? And is this the one that usually leaks?

The gasket set I was looking at on the the AutoZone site looks like it has a gasket that goes between the upper and lower sections on the manifold. Rock Auto sells just the manifold to block gaskets so maybe that's the way to go...

At least one writeup I read on this repair mentioned some o-rings (coolant) needing changing too. A new thermostat usually comes with a gasket so other than that gasket and the manifold to block gasket, are there any other parts you will be replacing when you put this back together?

And out of curiosity, how long did it take you to tear it down to the point illustrated? And what's the chain for?

Thanks!

I'm pulling that engine out. The intake came off in the process. It has a bad rod bearing so I'll need to pull that crank and have it re-ground.

Yes. the gaskets are right there in the second picture. Most gasket sets will come with more gaskets than you need. If the upper part isn't leaking, don't mess with it.

Looking forward to more rebuild pics, Fuzz!

Probably not getting a complete rebuild. Trying to avoid pulling the heads but if the rod that is knocking is out of spec I'll have to. Then I may as well hone and re-ring.

Anyway, not to hi-jack the thread. If you get stuck with your IMG job, I'll try to help.

I attempted this gasket replacement yesterday but I couldn't get the manifold to separate from the block. Here's what I did.

1. Disconnected the EGR tube - I was able to get a 7/8" wrench in there without much trouble. Since I thought this might be the most difficult step, I did it first.

2. Disconnected all the electrical connectors from the injectors. The back on the driver's side was a pain to get to. I saw a hint somewhere that said to press the tab with the short end of an allen wrench and that really helped.

3. Removed the top of the air filter housing and disconnected it from the throttle body. I also removed the bolts holding the accelerator cable and speed control cables, figuring this would give a little more room to maneuver the throttle body. I did not disconnect the very small coolant hoses from the throttle body because another post I had read said it wasn't necessary.

4. I was going to disconnect the fuel lines from the fuel rail but I couldn't see any way to get my hands down in there to reach the pinch clamps.

5. I tried to remove the allen head bolts holding the fuel pressure regulator in place but I couldn't get the accessible one loose and couldn't even see the other one that faces the firewall.

At this point I decided that I was going to have to settle for getting the manifold up only an inch or so since I was going to be restricted by the fuel rail and the fuel pressure regulator. Still, I thought I might be able to get the old gaskets out and the new ones in by 'feel'

6. So with some trepidation, I took the four nuts off the four bolts that hold the manifold in place. As a note to others who might try this, have a magnetic pick up tool handy because it is almost impossible not to have the nuts drop out of the socket once the are free of the bolt.

Now that I had everything loose, I was ready to pull the manifold. It wouldn't budge! There was precious little to pry against but I pried as best I could where I could -- NADA -- I could not get the manifold to separate from the block.

Ideas from anyone? Please!! Does the fuel pressure regulator have to come off? Are the fuel lines restricting me? How can I get to the clamps? Can they be reached from underneath the truck?

I put everything back together and started the truck. I was promptly greeted by error code 121 (Throttle Position Sensor) and the truck was running much worse than before. I double checked the connection on the TPS, and it seems to be connected correctly. Could I have damaged it while I was prying around? Anybody ever change one of these?

I need some help from you experts here or I may have to attempt a limp to the closest shop and pay the $400-$500 it will cost for this repair.

Thanks!!!

You didn't mention the removing the four long bolts in the middle. They are on each side in front and back of the pins that hold the plastic cover on.

I didn't see where you unbolted the throttle body. It is much easier if you unbolt (four bolts) and pull it forward, leave all the hoses connected. You have to unhook the two throttle cables.

Did you remove the four nuts AND the four bolts from the manifold? The four nuts are in the corners, the bolts are in the middle. It should lift easy because the gasket is metal.

I don't know how you removed the left rear nut without removing the regulator bracket, you must be very dexterous. To remove the rear cap-screw off this bracket use a short piece of hex (cut a hex key if you have to) and use a ring spanner of the correct size on the piece of hex.

You can do it without disconnecting any fuel lines, you'll need some rope or similar to hold it up.

Note that Isuzu lowered the torque spec on the manifold bolts to 13 ft-lb.

If you ever do completely lift the manifold it's a good idea to replace the o-ring on the heater pipe that goes into the base of the thermostat. The other one that goes into the crossover pipe under the throttle body sprung a leak on mine and I'm dreading the thermostat one failing.

Good luck

Andrew.

Boy, don't I feel like an idiot. I was only four bolts away. The weather has turned sharply colder here since Saturday so going back and hitting this again may have to wait until the weekend.

So is everyone in agreement that the fuel pressure regulator must be unbolted to get the manifold up far enough to get to the gasket (or pieces thereof)?

Thanks!

The weather warmed up so I made another attempt this afternoon. This time I removed the four long bolts. I tried to get to that back allen head bolt on the fuel pressure regulator but I dropped the allen wrench and I can't find it -- dang it!

I tried to get the manifold up enough to remove the gaskets. I got the passenger side one out but I can't lift it high enough on the driver's side to clear the back stud with the gasket.

I thought about trying to remove this stud but it's a Torx type head and I don't have anything to fit it. Will a 5 mm hex socket fit this?

I'm stuck here. It's too far apart to just put everything back together because there's a big hunk missing out of the driver's side gasket.

Any ideas? Thanks!

I wouldn't be trying to take studs out. When I did mine I put a step ladder either side of the engine bay. I ran a piece of 2 x 4 between the step ladders right across the top of the manifold. I then strapped the fuel rails to this beam. That way by carefully lifting the timber beam and packing under the ends I was able to apply a lot of lift without damaging anything, plus you have both hands free. You can get just enough clearance to lift out the gasket, but I did have the regulator bracket off, I'm not sure how much difference this makes.

Did you try cutting a piece from a 6mm allen wrench to use on the rear bracket bolt? Only needs to be 15mm or so long and you use it with a 6mm ring spanner. To get at this bolt you need to bend up the finger holding the vacuum hose and move the hose out of the way.

Good luck

'99.

I don't remember fiddling with a fuel pressure regulator.

If you have a Harbor Freight tool store near you, you can by a set of sockets that will have the size needed to remove the studs. I think they're only about $10 for the set.

99 Fronty: I bought a new set of allens and tried to cut the short end shorter as but since it is hardened steel, it just laughed at my hack saw. I did manage to get that bracket loose though. It didn't seem to give me any more lift on the manifold. Something fell out as I pulled the regulator out. It fell somewhere that I couldn't see. Any idea what that was?

Cat Fuzz: I did go to Harbor Freight to get the allen wrenches. I picked up a set of those Torx sockets. Since I still can't get the manifold up high enough to get the driver's side gasket I'm considering taking that back stud out.

Another option would be to remove the whole enchilada as you evidently did based on your photos. Besides somehow disconnecting the fuel hoses from the fuel rails, what else needs to come apart to lift the whole thing out. How did you manage to get pliers on those hose clamps?

I kind of wish I would have left this job to a pro but it sounded like it wouldn't have been that bad. Since a couple of chunks of the driver's side gasket have already come out, it's too late to just put it back together and take it to a pro.

Anybody have any idea why the gasket is a thick piece of plastic sandwiched between two thin strips of metal? Would rubber have been better than plastic? Was the torque spec lowered to prevent cracking the plastic, which seems to be the root of the leak problem.

Thanks!

I just managed to wiggle some needle nose pliers in there to grab the spring clamps. It was a hassle but I did it. Some angle needle nose pliers might work better.

Yes you need a cut-off wheel or angle grinder to cut the wrench, maybe you can take it somewhere?

I don't suppose the thing that fell was your original wrench?

When I looked at taking the manifold right off I was more worried about getting the hose clamps back on than getting them off. I thought I would rip them off any way I could and replace them with good quality worm drive clamps, the ones with a hex head. There is an arguement not to use worm drives on fuel lines as they don't 'self tension' so would be interested in others comments.

The gasket is strange, I don't know why it's like that. When I replaced the o-ring in the coolant crossover pipe between the heads, the pipe gaskets were thin metal like the metal part of the manifold gasket. Even worse they had a crinkly surface finish. I thought there is no way they would work, but they have sealed perfectly.

'99