Stumpped by low coolant level
Thread Starter
Joined: Dec 2007
Posts: 12,967
Likes: 389
From: Chicago, IL
Stumpped by low coolant level This one has me stumped. Anyone have any ideas?
I am getting a low coolant light on start-up. The FUNNY thing is it is a good sensor and the fluid is really low! (OK - Its not funny.)
I have replaced the radiator pressure cap with a GM part, tested the flow of the reservoir feed tube, and pressure tested the system. All three are perfect and there are no leaks - anywhere.
When the car is hot, the radiator level is full and excess fluid is discharged in to the reservoir - as normal.
Once the car is cool, the radiator fluid contracts, the level drops, but it does not pull excess fluid back from the reservoir.
I've tested the reservoir feed tube with a mighty-vac and it holds vacuum just fine. The only thing I can think of is a cracked nipple between the resovoir hose and the pressure cap. (Maybe at a high point that would not leak.) I'll test that tomorrow but am looking for any other ideas to try out.
I am getting a low coolant light on start-up. The FUNNY thing is it is a good sensor and the fluid is really low! (OK - Its not funny.)
I have replaced the radiator pressure cap with a GM part, tested the flow of the reservoir feed tube, and pressure tested the system. All three are perfect and there are no leaks - anywhere.
When the car is hot, the radiator level is full and excess fluid is discharged in to the reservoir - as normal.
Once the car is cool, the radiator fluid contracts, the level drops, but it does not pull excess fluid back from the reservoir.
I've tested the reservoir feed tube with a mighty-vac and it holds vacuum just fine. The only thing I can think of is a cracked nipple between the resovoir hose and the pressure cap. (Maybe at a high point that would not leak.) I'll test that tomorrow but am looking for any other ideas to try out.
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Joined: Oct 2009
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I had the same trouble and found the water pump gaskets were leaking. Another time I found a small leak at the water pump heater hose connection. Both time it did just like you posted, check for leak cold. I started the car with a cold engine and watched everything carefully. As soon as it warmed up the leaks were gone.
Thread Starter
Joined: Dec 2007
Posts: 12,967
Likes: 389
From: Chicago, IL
I was getting to that conclusion. I confirmed the entire system is tight, holding pressure with no leaks.
When the car is hot, there is no air in the system but the coolant is cloudy. When it sits, the siphon to the overflow reservoir is good and there is fluid in the tube.
It seems the fluid is holding air, which is settling out when it sits. The only thing I can think of is bad water pump seals letting air in and mixing it in to the coolant like a blender.
Does this sound right???
When the car is hot, there is no air in the system but the coolant is cloudy. When it sits, the siphon to the overflow reservoir is good and there is fluid in the tube.
It seems the fluid is holding air, which is settling out when it sits. The only thing I can think of is bad water pump seals letting air in and mixing it in to the coolant like a blender.
Does this sound right???
Thread Starter
Joined: Dec 2007
Posts: 12,967
Likes: 389
From: Chicago, IL
It was... the pump. Replaced it and the radiator is happy again.
Upon inspection, I didn't see any evidence of fluid coming out of the weep hole, but guess that a bad seal was letting air in and getting blended with the coolant.
Upon inspection, I didn't see any evidence of fluid coming out of the weep hole, but guess that a bad seal was letting air in and getting blended with the coolant.
I'm going to keep an eye on this thread, I had coolant and P/S contamination. I just changed to the non-p/s cooler hose and ran a separate cooler for its needs. I just need to see if that fixes my issues which were like yours, loosing coolant with no signs of leaks.
im in the process of doing the same thing, but where can i get a cooler??
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Thread Starter
Joined: Dec 2007
Posts: 12,967
Likes: 389
From: Chicago, IL
- A bad head gasket is letting in exhaust. (You can pressure test the cooling system to confirm.)
- The siphon between the expansion tank and the radiator is broken. (Hook another plastic tube up to the siphon tube and suck on it and see if you can hold that suction in the line.)
- The pump is pushing air in to the system. (Symptoms are like above.)
Regardless, the cooling issue needs to be fixed. Here's a thread that links to all the best info I've found on multiple options: https://ls1tech.com/forums/general-m...g-success.html
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