1990 C4 COOLANT LOSS

[Frank B.]

I'M LOOSING COOLANT ON MY 1990 C4, NO VISIBLE LEAKS ANYWHERE,REPLACED THERMOSTAT,GASKET,COOLANT FILL CAP,ETC.FINALLY BROUGHT TO DEALER HAD THEM CHECK ,THEY COULD NOT FIND ANYTHING EITHER.THEY PRESSURE CHECK IT SAID ITS FINE?
I HAVE TO ADD A 1/2 GAL. OF COOLANT AFTER 10-12 HOURS OF USE.HAS ANYONE HAD THIS PROBLEM?IS IT NORMAL TO LOOSE SOME COOLANT? ANY INFO WILL HELP...THANK YOU

[Wayne W.]

Re: 1990 C4 COOLANT LOSS

They have a tendency to leak at the rear corners of the intake manifold.

[Jean C.]

COOLANT LOSS

Frank, there is a GM product to stop small leaks. It is in tablet form and is added direct to your cooling system. Don't know the part number but I know Chevy dealers have it. I understand that dealer Service Depts. often add these tablets to any car on which they have worked on the cooling system or loosened cooling system components. Saves rework.

[Tom R.]

Re: COOLANT LOSS

My 90 did that and it drove me nuts. Finally as a last resort, I replaced the overflow hose that runs from the coolant tank to the radiator. The system was pushing coolant out but due to loss of vacuum...it would not suck it back into block.

Try a bypass with some hose and see if it corrects itself. The crimped metal on the hose may have a breach and therefore no longer maintaining a vacuum.

[Jim T.]

Re: 1990 C4 COOLANT LOSS

My 96's service manual reads to use a pellet supplement in the cooling system when changing the coolant. GM sells a packet of the supplement, think about five pellets to a blister pack available at any GM parts counter. If you use the pellets to stop the leak in your 90, recommend you crush the pellets before your install them and the car is going to have be driven to circulate the pellet material to stop the leak.
Check out Bar's Leak web page and check out the pellets they sell. I wonder if what they sell and what GM sells are the same product?
My son has a 96 Ford Windstar that has been loosing coolant for a couple of years and he tried two containers of the liquid Bar's Leak. He put it in and drove about two hundred miles back home and reported no coolant loss since before Christmas. His leak was internal going out the tailpipe and not in the oil.
Anyway my original owner 96 LT4 has no coolant loss yet and when I changed the coolant I did put in the pellet supplement as per the service manual. When I change my coolant I remove the knock sensors.

[Frank B.]

Re: COOLANT LOSS

Tom, thank you !!! that could be it.... I've noticed that the coolant tank has been very full...so i will try that this weekend I will post a message to let you know how I make out !!!

[Frank B.]

Re: 1990 C4 COOLANT LOSS

Jim,
thank you ,will try that also
Frank

[Frank B.]

Re: COOLANT LOSS

charlie,Thank you for the info

Frank

[Don G.]

Re: 1990 C4 COOLANT LOSS

Intake manifold gasket leaks are common on C4's. Occasionally, they will leak internally into the crankcase. An easy way to check is to loosen the oil drainplug after the engine has not run for 24 hours. Catch a small amount of oil in a jar and let it set. If there is any coolant in the oil, it can be seen in the bottom of the jar.