Lower Intake Manifold Surface – Chevy Blazer 2001

[fcobob78]

Hello,

I’m in the process of replacing the lower intake Manifold Gaskets on a Chevy Blazer 2001 V6 4.3, with about 130k miles on it.

I discovered after cleaning well the surfaces that the lower intake manifold has a substantial amount of pitting. I’m thinking this warrants a machine work?. I would like to hear people’s experiences with this. I read about smearing RTV silicone in this area, but the gasket instruction does not recommend this. Looking at the surface, it looks pretty beaten down, so I’m guessing a machine work is in order?

The surface of the block has some pitting but is not as bad as the lower intake, so I’m thinking on leaving this alone or using the RTV smearing method.

Another question is regarding the two rear coolant passages. Why does GM seals these passages? It doesn’t seem like the block had any seals, but rather was filled up with gunk when I cleaned. Just curious on why these are sealed. Is there any type of cement paste kind I can put in here to bring the sealed surface back to matting surface level? That surface looks pretty beaten down as well.

Hope the attached pictures help and I would appreciate any advise on machine vs silicone

Thanks,

Francisco

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Topic

[fcobob78]

Thanks. I’m going to pick at left hand drill bit. I already have a hole but that easy out didn’t do a thing for me and is becoming a nasty job. The hole is not very good as the piece of stud started to break, Im almost tempting to carefully break it down into pieces by drilling carefully. But like I said I think I still might be able to give the left hand drill bit a shot.

After getting it out what do you recommend for restoring the thread?

Thx for the help

[Its me]

[quote=”fcobob78″ post=115290]Thanks. I’m going to pick at left hand drill bit. I already have a hole but that easy out didn’t do a thing for me and is becoming a nasty job. The hole is not very good as the piece of stud started to break, Im almost tempting to carefully break it down into pieces by drilling carefully. But like I said I think I still might be able to give the left hand drill bit a shot.

After getting it out what do you recommend for restoring the thread?

Thx for the help[/quote]

After you remove the broken thread restorer, clean the hole out with a spray degreaser and then blast it with shop air while holding a rag over it to catch all the loose particles… Do this a few times… and ensure the hole is completely clean and dry (you don’t want to hydraulically destroy the hole)….. Then use a new thread restorer, turn a whole turn, turn back again and go slowly and deliberately, turn and turn back….. take your time… Nobody is timing ya!!! 🙂

-Karl

[EricTheCarGuy]

It may prove difficult to remove the thread chaser. It may require a special diamond drill bit in the end. I hope that’s not the case. That said it seems you have your work cut out for you and you know what you need to do. Good luck and keep us posted.

BTW also a little oil on the thread chaser is a good idea for future reference. Also cleaning the holes with a little compressed air before you start is also helpful.

[fcobob78]

Hello there I wanted to revive this thread. Thanks for all the answers and support. Finally I got the bolt out yay! I just have been so busy and put this off for a long time!. Anyways I wanted to share what I learned, so it might be helpful for someone. Also I wanted to ask a question after starting the vehicle for a long time and experiencing some issues.

Solution to broken bolt: I ended up using a drill called the rescue bit, it’s designed to cut metal and worked like a charm, however took lot of time and patience. After that I cleaned the threads really well using a new chaser and cutting oil. The issue was that I used the wrong thread chaser to begin with!. I used the metric thread and contacted bolt manufacturer and it turned out to be a SAE thread 5/16″ , what a mistake!. After that thread chaser did the work and restored all the threads.

Issue after starting vehicle: Now after putting all back together (what a piece of work), started the engine and started fine, but I can hear some knocking noises in the engine and started to see white fumes, I believe coming from under the engine where the spark plugs are located. No really struggles to start, started perfectly, just the knocking/rattle noise and the fumes. I suspect because the engine was sitting there for over 6 months?

After the engine was idle for a few minutes the noise went away and it seemed like the fuming stop, but then I accelerated the throttle body to a higher rpm , the knocking noise came back with fumes and the engine stopped. Started the engine back on (just with minor struggles) and the knocking noise and fumes were back and decided to stop.

What can be the cause of the issue? Is it a timing issue or perhaps a vacuum leak, old fuel issues? Any input on diagnosing this would be much appreciated. Thanks to all!

[Mike]

When you were farting around with thread chasers, broken tools, drills, metal chips, frustration and profanity, you did block the intake ports and coolant passages in the head with rags, didn’t you? Please say you did…or just nod your head quietly…

Also, could be that the torquing went wrong and you’ve got a coolant leak into the combustion chambers.

[fcobob78]

Hi, I did cover them with rag, but I admit some dirt and grit could have gone in there. I cleaned the area really well after using a vacuum shop, but again only what was visible and the vacuum could catch. I was hoping to get any of the stuff with an oil change. I really hope is not what you mentioned, but how do I diagnose this properly?

[Mike]

A quick first step would be to look for coolant and oil cross-contamination. Check the dipstick to see if there’s any whitish/cream-colored froth on it. Also, with the engine cold, open the rad cap and look inside the rad, stick a finger in there and look for gunk.

Some engines also require that the intake manifold be retorqued with the engine at operating temperature. That might be worth a try before you start taking things apart again. Just make sure you have the torque values correct and are torquing the fasteners in the proper pattern.

When torquing a series of fasteners, it’s a good idea to torque them down in progressive stages. Following the proper pattern, torque them all to 1/3 of the final value, then go over them again at 2/3 value, then finish off at 100%.

Hope this helps and avoids catastrophe for you.

[fcobob78]

Thanks. I did look at the oil yesterday to check the level and the color appeared fine, but I will also look at the coolant. I might be looking at re-torquing as well is worth the shot. I did follow the manufacturer three sequence torquing specs and pattern when I installed it.

By doing some research Im suspecting it could be a vacuum leak or a fuel problem. Accelerating stalled the engine, which makes me wonder something is happening in the combustion fuel/air mix?

[fcobob78]

Update: Changed the oil as it was really old and added 5 gallons of high octane fuel, as the fuel was really old as well. Check the oil level and new oil looks really clean no signs of coolant. Also it appears no coolant leaks any longer through the manifold.

These are other items I noticed:

After changing the oil and adding new fuel it seems the engine like it a little better. Knocking noise went down when idle but it is really bad when accelerating. Also when accelrating at about 1500 rpm car stalls. It held out fine at about 1000 rpm.
Fumes stopped, Im guessing this was due to the new silicone or some oil drips from when I was working on it.
No overheating, as stated above, no coolant leaks. I brought it to operating temperature, and it seems like the knocking noise goes down in a idle when the vehicle is warm.
This morning I fired up (cold engine) and noticed the knocking was more noticeable while vehicle in idle but still better than before and also noticed hesitations like wanting to stall but it didn’t while idle. It appears that once the engine is warm, the engine runs pretty smooth in idle.

What would be the next step to check for here? Perhaps timing, air flow or fuel delivery?

Any help would be much appreciated I would like to get this car back on the road!

[fcobob78]

Another update… I found some air noises on my vacuum hoses and some need to be replaced (pretty rotted). I also believe the routing of the hoses is wrong as I tested the 4×4 and it didn’t engage and triggered the engine service soon light. Could a vacuum leak cause the vehicle to stall at certain rpm?

[Author]

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