I'm a fairly new Corvette owner. I've had the car for about 6 months and this is the first problem I've had. The car is a red '89 coupe, L98 auto, w/ 67k miles.

I've searched the archives and found several possible causes, but none that suggest the most common or what to try first.

My problem: For the last couple of weeks I've been smelling antifreeze when the car is hot and I stop at a light or pull into my garage. Today, I took the car for a drive, city (stop & go) then hiway for about 45 mins. While on the hiway (about 10 mins from my destination) the low coolant light came on. I stopped immediately at a "Stop & Rob," filled up the overflow tank from their hose, and bought a gallon of water just in case. I continued on toward my destination and the light came on again. I stopped and poured a little more water into the overflow, which was still full. The light went out and did not come on again. However, I did notice antifreeze pooled in the valleys of the intake manifold on the driver's side. I continued home and parked the car for about 45 mins. I went and checked and all the antifreeze had either evaporated or drained off. I tried to recreate by running the car to operating temp w/ the heater on but the antifreeze didn't pool up like I saw earlier in the day. I believe there was a hint of antifreeze/water beginning around the front two intake torx bolts just under the TB, but I couldn't let the car continue to run because I had to pick up my daughter from school. During this entire time the operating temps stayed normal (I think). 190-195 hiway & 200-210 in stop & go.

Should I start w/ tightening the intake torx bolts? If so, do you have to remove the TB and plennum? Some of them look impossible to get to w/out doing this. What else should I try? It didn't appear to be coming from the thermostat or TB coolant line. I think these would be fairly obvious to spot.

If I take it to a shop or dealer, any idea what kind of pricetag I'm looking at?

Thanks in advance for any info or advice.

Hap :seeya

 

You can try to tighten the bolts, but I believe you are looking at replacing the intake gasket. SBCs are notorious for these type of leaks.

 

You may be lucky and have a Throttle Body coolant leak. The throttle body's front plate is the area where coolant circulates. They don't seem to leak all that often, unlike the intake manifolds. If you have coolant showing up on the throttle body, would start there first. I would submit if the manifold is leaking, the fluid would not likely migrate upward towards the throttle body. You could have two things leaking. Standard gaskets sells a throttle body gasket kit. Believe it or not, the NAPA folks couldn't find a gasket set for TB only, part of the intake gasket set. If the throttle body is removed, best clean everything up since you have it removed.

Good luck with your repair.

dlmeyers 90 coupe zf6 3 speed shocks

 

Good call. I hadn't thought about that as I have had my TB bypassed for some time.

 

If you find loose intake base bolts you can remove them, clean and coat the threads with some Permatex #2. Then torque them progressively to 35lbs-ft; use a high quality T-45 Torx bit so as to not scuff the bolts.

If you need to have the intake base removed and resealed by a shop I would bet on 4-6hrs of labor and maybe $100 in parts.

 

Is it safe to drive in this condition as long as I keep an I on the coolant level?

I am very meticulous about checking fluid/coolant levels frequently.

 

Well "safe" is relative.

The L98 cooling system uses vacuum to pull coolant from the resevoir at appropriate times. So a leak that breaks this closed system prevents the coolant in the resevoir from being pulled back into the radiator.

I suppose if you keep spare water with you and monitor the low coolant light you can drive it. That being said...I too have a coolant issue that prevents coolant from being pulled up from the resevoir so, though the low coolant light is on, I monitor coolant temp to avoid disaster.

 

:iagree: Tightening bolts at this point is probably pointless. These things do develop intake manifold leaks and sounds like what you have!

:seeya

 

you thermostat gasket may be bad or the hose is leaking at the connection spraying water back into that trough.

Sounds good anyway.

 

Replace the thermostat gasket first. If the intake gasket is leaking, the water has already created a path and retorquing the bolts will not stop it. Be careful of the thermostat bolts, they corrode and can break off easily. Good luck.. :chevy

 

How far down the valley did the water go?
I had the same problem after I put a dry gasket in the T-stat housing. Once I replaced the $6.00 gasket with a $1.00 one with some RTV, I was good to go.
Good luck.

 

Did you check the hose fitting to the thermostat housing? I had a 5.7 liter in a chevy van with a casting ridge on the housing and leaked until I smoothed it out. Coolant would pool in the front valleys around there. That said, when I got my 85, I could loosen the intake manifold bolts with two fingers, cant count the number of leaks there. For that I decided to have the block bored out and stroked, and.... well it was probably overkill for a leaky manifold. :crazy: :lol: