Hi guys

In October of last year, I replaced the head gasket on my 1993 5.7L Trans Am. Everything was great until earlier this month when I noticed that I was losing coolant. I saw some hoses that appeared to be leaking at the clamps and I replaced them. In doing so, I also replaced the thermostat and the water pump. I tested the new thermostat in a pot of boiling water, and it tested good. Immediately afterwards something different started happening. On a daily basis I'm finding a puddle of coolant under the reservoir tank. The radiator is low, and the reservoir tank looks overfilled. In fact, the coolant seems to be coming out the top of the reservoir tank, and leaking on the ground. There is no coolant in the oil, and the car is not overheating. I do not see any coolant or white smoke coming out of the exhaust. I also pressure tested the system and found no leaks and it held 18lbs of pressure. All the coolant lines are attached to the right places, including the reservoir line and the steam pipe line. The cap appears to be in good working order.

Would anyone have an idea of what could cause the coolant to be backing up from the radiator to the reservoir on a daily basis? It's a PITA having to fill the radiator up every morning!

Thank you so much in advance

 

Did you replace the thermostat with an LT1 specific unit? It isn't the same as a conventional thermostat. The LT1 utilizes a reverse flow cooling system, and requires a thermostat for the LT1.

 

Are you refilling the radiator each time you find it low?

Check the overflow line from the fill neck to the reservoir for damage. If there is a leak in that line, the vacuum that forms in the radiator as the coolant cools down and contracts, can't pull coolant from the reservoir to refill the void formed as the coolant cools down.

Also, check the metal tube on top of the reservoir for holes. At this point that piece is starting to show problems with corrosion.

 

I would replace the radiator cap, making sure to use the correct one. The cap has two functions, each with separate parts. One is to hold the pressure to a pressure point and then release the coolant to the overflow reservoir at a higher pressure point when needed. Later when the coolant cools and contracts, a separate vacuum valve in the cap opens to let the coolant back into the radiator. Perhaps the cap has damage or a defective vacuum valve.

 

You can take GaryDoug's advice to the bank.When I had my radiator serviced they put on a stant cap and the problems began.I replaced the cap with a genuine ac delco exact replacement cap and that fixed that.Hope this helps.