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Discussion Starter #1
OK, so I am replacing the lower intake manifold gaskets on my 1997 S10 with V6 engine. The truck had been leaking coolant and it is time.

I have gotten everything apart. The original gaskets were definitely bad, several breaks in the gasket and plastic backing material.

I am now cleaning the lower intake manifold. As I have gotten the mating surfaces mostly clean, I have noticed that the metal seems corroded around the coolant ports. It seems the worst corrosion is around the "dummy" coolant ports at the rear of the LIM. The corresponding dummy coolant ports on the engine were filled with coolant slime. These rear cooling ports just hit a dead end at the LIM.

I am not sure how to proceed at this point. Should these mating surfaces on the LIM be sanded and polished? If I installed the LIM as it is, would the new gasket fail to form a seal? It seems the worst corrosion is around the "dummy" coolant ports at the rear of the LIM, but there is some corrosion around the front coolant ports.

Thanks for any feed back.
 

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Those don't look very bad. Don't "sand" and polish aluminum you could created low spots. If you want to smooth it a bit use a fine flat file and lay it flat against the manifold, then move it back and forth to clean it up as much as it will allow. If you use the top of the line replacement gaskets they will compensate for minor imperfections. Cheap ones will fail again.
Check the surface of the heads also. I have an L31 I got cheap because the second set failed and he just replaced the engine. It needed a new head on one side because the cast iron was seriously pitted. I ended up with a good Vortec 5.7 for less than $200 total.
 
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Discussion Starter #3 (Edited by Moderator)
Those don't look very bad. Don't "sand" and polish aluminum you could created low spots. If you want to smooth it a bit use a fine flat file and lay it flat against the manifold, then move it back and forth to clean it up as much as it will allow. If you use the top of the line replacement gaskets they will compensate for minor imperfections. Cheap ones will fail again.
Check the surface of the heads also. I have an L31 I got cheap because the second set failed and he just replaced the engine. It needed a new head on one side because the cast iron was seriously pitted. I ended up with a good Vortec 5.7 for less than $200 total.
The gasket set that I bought is Felpro MS98002T. I've seen these as recommended replacement gaskets for this engine, due to the tendency of the old ones to rot out.

The head is in better condition. There is some minor pitting around the coolant ports, just inside where the old gasket was. If I run my fingernail across it, my nail just catches. I'm guessing the pitting is less than 1/100th inch deep. It shows up as a dark line in the photos below.

I can understand not sanding the manifold surface. I imagine having to take it to a machine shop and having a precision surfacing machine smooth it out to keep the surface level. I'm not sure if this is possible or worth doing. I would just hate putting the engine back together and it still leaks.

Photos below are front and back cooling ports on head, driver's side.
manifold4.jpg
manifold5.jpg
 

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Mine were like that also. I used some high heat copper silicone and pressed it in the imperfections with a utility blade. No issues.
 

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Discussion Starter #6
Update!
Today I have finished putting the S10 back together. I followed the procedure in the Hayes manual and online resources. To deal with pitting of metal, I applied a thin coating of RTV on the gaskets around the coolant port openings. I bought a new set of bolts with thread sealant pre-applied, instead of reusing the old ones. Not sure if that is necessary, but they weren't expensive. Also important I felt, was to buy a 5/16"-18 thread cleaning tap. I used the thread cleaning tap to ensure the bolt holes were totally clean.

I'm inexperienced with this type of auto repair, so I work slow, it took me 8 days. But only working a few hours a day on the weekdays. Probably one third of that time was cleaning parts.

When I started the S10 for the first time it squealed loudly. After adjusting the serpentine belt tension, it ran great! Before the gasket repair, there was a very slight roughness to the idle. I think that is improved. It runs very smooth now. Let's see if there is improvement to gas mileage.

I drove it 10 miles today. No problems. Maybe tomorrow I will change the oil to get out any dirt that fell into the engine.
 

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Should have replaced the spider while you had it apart.
 

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If the poppets haven't clogged yet...the will. The upgraded spider uses real injectors. Makes for a smooth running engine. Maybe yours have already been replaced. AC/Delco...$224.

 

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Discussion Starter #10
If the poppets haven't clogged yet...the will. The upgraded spider uses real injectors. Makes for a smooth running engine. Maybe yours have already been replaced. AC/Delco...$224.

No, I don't think they have been replaced. When I had it apart, I looked at the injectors. They are the original design. I don't think it is necessary to replace them at this time, at least not for $224.
 

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No, I don't think they have been replaced. When I had it apart, I looked at the injectors. They are the original design. I don't think it is necessary to replace them at this time, at least not for $224.
The fuel pressure regulator is on the back of the spider. That thing is notorious for leaking and it's inside the #$(*& plenum.
 

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the upgrade is absolutely worth the money. My 02 blazer was one of the last ones that used poppets and I upgraded them during a LIM job about 6 months ago. Mine seemed to be running just fine(except for the lim leak),but I figured "might as well". WOW what a difference in performance(not race car kind of performance mind you) and the gas mileage increase will definitely pay for this quickly-if it hasnt already
 

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Discussion Starter #13
The fuel pressure regulator is on the back of the spider. That thing is notorious for leaking and it's inside the #$(*& plenum.
I had read a lot about replacing the LIM, but I hadn't read anything about the fuel injectors or fuel pressure regulator.
What goes wrong with the pressure regulator? Is this something that can be tested for with a fuel pressure gauge?

I already have the S10 back together, so too late for me. If I was to replace the injectors or regulator, is the plenum gasket reusable, or does that have to be replaced when the plenum is disassembled? I installed the Felpro gaskets. The plenum gasket appears to be made of a pretty sturdy silicone-ish material.
 

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The upper gasket is reusable as long as it's not torn. No need to mess with the lowers.
 

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I had read a lot about replacing the LIM, but I hadn't read anything about the fuel injectors or fuel pressure regulator.
What goes wrong with the pressure regulator? Is this something that can be tested for with a fuel pressure gauge?
There's a diaphragm inside the FPR that starts leaking. It's visually evident in the intake because it'll drip gasoline onto the aluminum below it and that will clean the oil residue that's super-evident everywhere else. You can check for fuel system leaks with a fuel pressure gauge, but you won't be able to distinguish between a spider leak and an FPR leak without taking the plenum off. Since the FPR comes with a spider, it's simpler to replace the assembly, at which point, upgrade to the ACDELCO individual injector assembly.
 

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Discussion Starter #16
There's a diaphragm inside the FPR that starts leaking. It's visually evident in the intake because it'll drip gasoline onto the aluminum below it and that will clean the oil residue that's super-evident everywhere else. You can check for fuel system leaks with a fuel pressure gauge, but you won't be able to distinguish between a spider leak and an FPR leak without taking the plenum off. Since the FPR comes with a spider, it's simpler to replace the assembly, at which point, upgrade to the ACDELCO individual injector assembly.
When I disassembled the intake manifold, it was not clean. There was soot build up. All surfaces were black. So, maybe not the pressure regulator. I will look at the issue more.
 

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When I disassembled the intake manifold, it was not clean. There was soot build up. All surfaces were black. So, maybe not the pressure regulator. I will look at the issue more.
If you really didn't have a clean spot behind the spider (and below the FPR), then your FPR is fine.
 
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