Wayne Alegre

Greetings.
I recently purchased a 91 Corvette L98 with 84,000 original miles. I went out and started it today to take it for a ride and noticed it was leaking anti freeze from the left side of the engine and appears to be behind the cylinder head. Not sure if it's the intake manifold or cylinder head. Has anyone experienced this with the L98? If so I would appreciate any feedback or suggestions as to how to properly diagnose since I really can't determine where it's coming from.
Thank you in advance for your help and suggestions.

Jstan2014

Mostmint

Agree with above post. People do spend time browsing the technical forum that do not visit the Intros forum.

Vetteman Jack

Moved to the C4 Tech section.

Kevova

Coolant pressure test. Some parts stores have them on loaner programs. Intake gasket or freeze plug very possible. Removal of bell housing cover and a " mirror on a stick" can be aid is locating leak. Head gasket less likely but not impossible.

Wayne Alegre

I was really upset about this yesterday and probably wasn't thinking right. I appreciate your advise and I will take care of this today to see where it's coming from. I will let you know what I find after doing the pressure test on her.
Appreciate your advise..

vetteman42

If intake is leaking ..........check "bolts" as mine worked loose years ago causing leak. If not loose, new gasket needed.

Wildride

A known and common problem with nearly all L-98 engines that occurs between 60000 and 100000 miles. The Intake Manifold "China Wall" gasket and sealant breakdown and anti-freeze starts leaking out. Usually just a small drip at first. Google "L98 engine china wall leaks" and you will find pics and more info.

I repaired mine at 69000 miles and used "Right Stuff" sealant. This was in 1999. No problems since.

Twenty years ago this was a frequent subject on the Forum. i suspect that most have been repaired by now but there are always a few lower mileage cars out there.

VikingTrad3r

xrav22

I was at 170000 when my intake gasket blew in the right front. I tightened the neck area to get buy but when I did the intake(not to hard I did it on the street) I found most of the bolts loose.
Alot of them. You could try to tourque the bolts but you are only a dizzy away from removing the intake. Mabey hose pinhole and squirting. Good Luck!

ToniH

Its also really common on L98's to blow driver side head gasket. When fixing that you obviously need to take the intake off. And while putting it all back together there is a risk of putting intake bolts back in wrong order. There is couple which have very minute length difference. If you put the wrong one into the hole closest to the windshield it will bottom out and you think its torqued when its really not. And then you have a coolant leak at the rear of the intake on driver side. Can happen on other side too.

Ask me how I know

VikingTrad3r

ToniH

In my '91 it was so but its the only L98 I've touched so cannot say if all have this issue or different years are somehow different (?). The bolts were so close I didn't originally realize they were different. But after we tore it all open again to find the cause and fix the leak we realized what happened. I tried it, the bolt bottomed and left the intake rear corner loose. Swapping the 2 bolts solved the issue and no more leak!

So, I cannot be sure this is an issue with all cars but something to keep an eye on when assembling the intake back on the motor.

ctmccloskey

When the thermostat housing gasket starts leaking the coolant flows down the left side of the motor and drips off the heads because the car moving forward pushes it back there. Just a thought... It was leaking on mine and that is where I saw the leakage dripping off as well, fortunately I had a trail to follow. Take a close look at the thermostat gasket and the hoses supplying coolant to the throttle body as they both are prone to leak.

My 1988 C4 had a coolant leak on the part that attaches to the bottom of the throttle-body. There are several places the coolant may have come from the front of the engine. Don't forget that many of the C4's have a Coolant temperature sensor in between number 1 and Number 3 cylinders, some times the sensors will leak. There is another temp sensor on the front of the motor that could leak. Dry it all out and wait to see where it comes from.

I wish you the very best in finding the leak you have and hope it doesn't require pulling the heads off the car.

Wayne Alegre

I appreciate all the feedback from everyone. As the leak came, it stopped by itself and has not done it since. I dont know what caused it to leak but I know it's not leaking anymore! I checked the antifreeze and found it to be full so as the old saying goes, "if it ain't broke don't fix it". I'm not gonna bother with it mechanically unless it does it again. But that doesn't mean I'm not curious as to where the leak was cause I am.