88 C4 Coolant Leak

Spring is here and I brought the 'vette out after her winter storage. I'm the 2nd owner having acquired it summer '90 which now has 180,000 Km / 110,000 miles on this auto coupe with the Z49 option.
First thing I noticed was a very slight fluid leak under the car that appears to be coolant dripping off the oil pan.
Second thing I noticed was the DIC telling me I had LOW COOLANT that was ON / OFF - mostly ON. Last time I noticed this symptom was years ago and only when driving through the New England mountains.
Checked the rad level and overflow tank - rad good, overflow way down - and no oil that I could see. Checked the underside of the oil filler cap & the PCV valve - everything looks clean and no sludge. Can't see any obvious leaking points checking the block, hoses, rad, etc. No signs of contamination in oil -- not off-white / creamy.
Am I looking at the initial / middle / final stages of an intake gasket leak i.e. coolant leaking into the engine ? If so anyone able to advise on any long term engine damage ?
She'll stay garaged until I can schedule some shop time.
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Vette88 wrote:

Not to put a damper on an otherwise great wrench-bending session but, how about a pin-hole leak in the upper (left side) radiator hose?
--PJ '89 HookerCar, '02 e-blu 6-spd coupe
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Hope it didn't freeze in your storage!
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I have had several coolant leakage problems with my '87.
I had a frequent small pool of coolant at the right rear of the intake manifold next to the head. It was a small leak and no coolant showed up in my oil, but occasionally you could smell the coolant. I lived with it for years until I removed the intake manifold and replaced the gasket. I used GM grey silicone on the gasket and tightened the bolts carefully (with thread lube) and a little tighter than spec. This job is a lot easier if you have a very long T40? Torx wrench for the manifold bolts. It solved that problem which I have been told is very common in these cars.
I also replaced the vacuum operated valve in the rigid coolant line leading to the heater. The valve is used to stop coolant flow to the heater when using the air conditioner. It is a poorly made valve and I tried to repair it but the cheap plastic valve is not available and I was unable to find a replacement seal, so I bit my lip and purchased the complete dual tube assembly from GM for way too much money.
There is a service letter regarding the low coolant light. It is document ID #268592 the title is 'low coolant warning light may be caused by trapped air #88-43-6B' You should be able to get a copy of this letter from any good GM dealer. I do not have a URL for a GM knowledge base to access this type of service letter on the web. If someone knows how please post it here. I did purchase the spec clamps but they are just normal heavy duty worm screw clamps.
I understand there is also a common leak from the water pump mounting surface which is also fixable with a simple gaskets change. I have noticed some drops of coolant under the front of my engine but I will live with it for a while.
I am inclined to think that the aluminum thermal expansion cycles are the cause of most of these leaks and that the cure is a THIN layer of silicone on both sides of the gaskets and a little extra torque when tightening bolts. I suggest tightening the bolts then letting them sit overnight to let the gaskets and silicone to flow a bit and then retorquing them before completing the job. I am also a big believer in using a nevr-seize type thread lubricant on the bolts to improve the clamping force.
It is nice to get all the little leaks fixed but it was a lot of work and the air conditioning heater valve was very expensive.
Good luck, YMMV
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