Intake gasket and possibly the intake

chevrolet
1500
gaskets

#1

OK everybody - you have a rookie on your hands as far as this web site goes. The truck is a 1997 4WD Silverado with 189,000 miles. I have been told that the reason my temperature gauge keeps going way up then way down the last few days (sometimes with heat and sometimes not) is that my coolant is low (and it was). I found out this morning that I have to have the intake gasket replaced for around $600. I may also need a new intake depending on how it looks (amount not discussed at this time thank goodness). I would also like to say that this small repair shop has been very good to me over the years. My questions are 1)Does this sound like a fair price for the gasket, 2)What is a fair price if the intakes have to be replaced, 3)Is this the same thing as a head gasket, 4)I thought I just went through this a couple of years ago but it may have been some other expensive gasket (is this possible), and 5)I was told that the green coolant was OK to use now instead of the orange. Any knowledgeable comments would be appreciated.


#2

The intake gasket is between the intake manifold and the head. The head gasket is between the head and the block. The exhaust gasket is between the head and the exhaust manifold. The valve cover gasket is between the valve cover and the head. The gasket itself is not the expensive part, though cost for gaskets have risen sharply in the past few years. The main cost is labor.
If the engine overheated, the intake manifold might have warped. That could cause the gasket to leak. This would be a vacume leak, and there would be associated symptoms such as the engine idle being uneven, and a hissing noise, etc. I doubt if this would lead to the temp gauge behavior. That is more likely caused by a faulty sender or loose wire or bad ground or even rarely a bad indicator. The low coolant will also have a cause and it is not likely to be the intake gasket, though some vehicles do have coolant chanels in the intake manifold to adjust intake mixture temp. In than case the answer could be yes you might need to replace the intake manifold coolant gasket. You need to check the service manual on your engine to determine if this is the case.


#3

This is a common problem on these engines. The intake plenum and intake gaskets are totally seperate from the head gaskets.

What usually happens with these intake systems is if the plenum fails it’s due the EGR gasses passing through the plenum. These EGR gasses erode the EGR port in the plenum where it breaches into the coolant jackets that are supposed to keep that area of the plemum cool from the hot EGR gasses.

If the lower intake manifold gaskets fail, it’s due the difference in the coefficiance of expansion between the aluminum lower intake manifold and the cast iron heads. This difference in expansion rate causes the silicone seal part of the gasket to delaminate from the plastic frame of the gasket. The gasket then begins to leak.

So if the upper intake plenum is the source of the leak, also replace the lower intake gaskets.

Tester


#4

Thanks. After reading your comments, I believe it was the exhaust gasket that was replaced a couple of years ago. I remember many parts laying about so I assumed the major cost was the labor. There has been no uneven engine idling and no hissing that I could detect. I will ask about the possibility of a faulty sender, etc. while he is already in the motor. Thanks again for your expertise.


#5

Thank you Tester. I will bring that up this afternoon. Let’s hope the gaskets are the only problem at this point.