Intake Manifold Repair

I think I've narrowed my starting and oil pressure/coolant problems down to a faulty EGR plenum in my upper intake manifold. The parts I can get for $100 to $200, but the local shop wants over $500 to do it. The repair itself looks easy, but I don't know how hard it is to take apart the manifold.

Can anyone offer any advice about this?

Thanks!

Tom

Well since you didn't give a year, make, or model of car I will assume it is a 3.1 liter. The upper intake plenum is pretty easy to get off however I don't know why an egr problem would cause an oil pressure issue. Or a coolant issue. These motors have been known to have problems with the lower intake manifold gaskets failing which can be quite a job if you are inexperienced. Anyway, no oil or coolant flows near the egr valve. I would like some more info on your problem if you wouldn't mind.

Wow, I can't believe I left all that info out. It's a 2001 SS, so a 3.8L. I've had it not start on my twice in the last couple weeks. New battery, and I can here the starter hum but no movement or cranking to turn over. If I try enough times it suddenly fires up fine. Twice now after I've been driving for about an hour, my low coolant warning comes on, even though I have plenty, and then goes off.

From what I've read, this is a known problem of the plastic upper intake they started to use. The plenum degrades over time and can leak coolant into the intake and cause vapor lock. Which is why I believe the UIM plenum is failing.

This doesn't sound like hydolock, if it was that bad, you would have damaged the engine by now, I doubt you have a problem like that. Its possible, but I doubt it. If you have coolant in the combustion chamber like you state, your coolant would be down a lot. Also, when you start it up, it would puff a large amount of white smoke as it burns off the coolant in the engine, so take a look and see.

You could have a gasket leak, in which case if your not sure, have the cooling system pressure tested, a leak down test, at a shop you trust. If the system isn't holding pressure, then start looking fast.

You mention the oil pressure, whats happening with the oil pressure? Do you have low oil pressure? Any knocking, any engine noise. Oil pressure is usually an indication of coolant getting into the oil and destroying your bearings.

My advice would be to get the coolant system checked right away and see if infact you have a problem, if you do, do with you have to to get it fixed. If you have a inatke gasket leak, or maybe even a head gasket leak, don't drive it like this, because you will destroy the engine. The oil pressure point you mention has me concerned, Get it looked at ASAP.

The oil pressure fluctates with acceleration, varying noticeably especially when driving in the city. It holds pressure when at a constant speed. It never really drops to low or peaks too high, but the needle definetly moves up as I accelerate and drops when the RPMs drop.

Increasing oil pressure with increasing RPM's is normal, is it not? The oil pump is spinning faster with higher RPM's.

yea, the oil pressure needle will fluctuate with driving. I haven't heard of too many problems concerning intake gaskets on the 3.8s, mainly just the 3.4s and 3.1s. But if you actually are loosing coolant then do what blazes9395
said and have the cooling system pressure tested. I fixed a coolant leak on a 3.8 the other day, it was the thermostat housing. These motors also seem to have problems with the valve cover gaskets leaking but that is oil. Chances are it is something not to serious. Those are pretty solid motors and not too bad to work on.

About your starting problem, kinda sounds unrelated. If the starter spins but doesn't engage the ring gear on the flexplate then that is a problem with the starter/flexplate. Most likely the starter. How many miles are on this car?

p.s. white smoke out the tail pipe is a sign of burning coolant.

I've got over 124k on it. No major problems until now. I felt ambitious so I plunged into looking at the gasket. I've snapped a couple of photos of the old upper intake and the lower.

Have a look
http://flickr.com/photos/88653821@N00/

See anything out of place? I'm going to clean up the lower intake and put on the new upper (might as well, I paid for the part already, just to avoid future problems).

I noticed a few of the bolts holding the UIM were looser than others. I also noticed some oil in my coolant when I drained my radiator down a bit. Once I get it back together, I'll get it pressure tested.

Remove all the old spark plugs and pitch them.Have someone roll the engine over with the key to get the coolant out of the cylinders after being put back together.Put in new plugs,put in AC Delcos and change the oil too.The ones I done,the plugs and the oil/filter had to be changed.I done them in the Buicks and Pontiacs,they would not start with the old plugs and ran after putting in new plugs.

The plugs and wires were replaced at 100k.

Does anyone think it's a problem I have oil sitting in my lower intake manifold? It's enough to cover up the bolt on the insided holding the LIM on. Should I take the LIM off, clean it, and replace the gasket between it and the cylinders? Or just sop up the oil and degrease what I can, without getting it into the intakes? As you can see from the pics linked to above, my LIM is pretty black. I will be replacing the PCV valve.

Thanks