This one has me stumped. My 94Z with 169,000 miles on it has finally got me.

It appears that the coolant is going into the coolant recovery tank and not returning to the radiator. Mainly happens when the car runs warm, just cant figure this one out. There are no signs of leaks anyware, I changed the rad cap, flushed the coolant overflow, flushed the system, changed the thermastat and even had the radiator checked while running for exhaust gases (figuring maybe a head gasket). Its had this problem for months and I just cant figure it.

I'm thinking maybe i'll change the water pump next.

Anybody have any ideas? Thanks

 

I just spent another hour looking everywhere and I can still find no signs of leaks. Even the weep hole under the water pump is totally dry. Hasn't anybody had a similar problem?

 

You may want to check and be sure that the coolant overflow hose from the coolant recovery tank is connected to the radiator properly. The coolant overflow hose should connect to the upper port beneath the radiator cap. The port on the radiator below that should connect to either the throttle body or the steam vent line. Shoebox has a picture here:

http://shbox.com/1/93-94_hoses.jpg

Just to clarify, based on this picture, hose #27 should be connected to the upper port on the radiator just below the cap. Hose #4 connects to the port below that.

Your symptoms are similar to those experienced when these hoses are swapped. Hope this helps.

Brian

 

In order for your coolant to return into the radiator your system must be totally sealed. The way I see it you have one of two problems. A leak in the system or a faulty radiator pressure cap(well, I guess that is a leak in the system..hehe).

Get a Cooling system pressure tester. That will help you see if you have a leak in the cooling system. This device replaces the radiator cap and allows you to pressurize the system to the levels on the pressure cap. I rented(bought) mine from Autozone....as a matter of fact I kept it, because I liked it so well. You can also test the pressure cap as well with this too. However, caps are cheap. I'd just get a new one and make sure that where the cap seals to the radiator is completely clean. This is provided that that your system holds pressure without leaking.

Also, GM has pellets that seal minor leaks in the system. P/N 3634621

GM recommends adding 2 pellets(crushed up..not whole) to the system under the following conditions:

1. Vehicles encountering water pump seepage or minor coolant leak/loss that cannot be corrected through normal service procedures.

2. When cooling system is drained and coolant is replaced with new coolant due to engine repair or at recommended coolant change intervals (five years or 100,000 miles).

3 Whenever engine water pump is replaced. The addition of pellets provides a mild lapping of the new water pump seal that improves conformability of the mating surfaces. Water pump seal seepage is minimized by the addition of pellets.

All of the above is from a 1996 GM F-body service manual.

IMHO, it has to be a leak somewhere.

 

A simple crack in the hose connecting the radiator overflow connection to your overflow tank can cause that problem. Coolant gets hot, expands, flows through the pressure cap and down the hose into the overflow tank. Radiator cools off, vacuum builds in the radiator, and the pressure cap opens to allow the vacuum to pull the coolant out of the overflow tank and back up the hose. A crack in the hose breaks the vacuum. Might be worth checking the overflow hose for cracks.

 

Ditto on Injuneer's comment.

My car experienced the same problem. Drove me crazy for weeks until I removed the battery and saw the coolant overflow hose was discolored. I bought a new hose from the dealer and never had another problem.

Thomas.

 

i have the same exact problem only happens after the car runs for a long time and then my coolant light will pop on, ill check out the hoses tomorow finally got a day off

 

I removed the bottle and checked the hose running to the overflow. Looks fine (I even flushed it out while I was at it). I'm thinking of changing the water pump and doing the pellet trick (maybe that will work, water pump is old anyway what the heck), looks like an interesting weekend.

 

Where did you get the new radiator cap? I replaced mine a while back, and heard bad things about non-dealer caps; so I got one from the dealer. I don't remember the price, but it wasn't too expensive.

If the overflow tank is not leaking, the overflow hose is not leaking, and the cap is working correctly, you must have a leak somewhere else. I would not recommend the stop leak pellets (even if GM says they're ok). It's better to find the leak and fix the problem. Get yourself a radiator pressure tester and pressurize the system to find the leak.

Good luck!
Thomas.

Interesting thread on radiator caps: http://camaross.com/forums/showthread.php?t=427546

 

I go tthe cap from chevy, I think I was wrong though, I just added about 2 qts of coolant to the radiator. So much for my theory of it going into the overflow. I'm beginning to think head gasket even though it passed the chemical test (no signs of exhaust gasses in the rediator at all. ).

Anybody else have any ideas on where to look?

 

I assume you looked at the oil for any signs of coolant. So have you pressure tested the radiator to see if it holds? Pulled any plugs to see if they show signs of burning coolant? Does it run rough or noisy until it warms up then runs smooth?