Strange Coolant/Cap/Overflow Tank Problem
Thread Starter
Racer
Joined: Dec 2003
Posts: 349
Likes: 0
From: Hong Kong
Think I finally pin pointed the problem here.
I added some red UV dye to the system to see if there were any leaks, I didnt even need a UV light to see, have a look at the below images...
It seems that the expansion tank is getting old and leaking a small amount, which probably is why there is vacuum, but not enough to suck back from the overflow tank.
I'll order a new expansion tank and re-post the results. Cheers for all the help so far!
I added some red UV dye to the system to see if there were any leaks, I didnt even need a UV light to see, have a look at the below images...
It seems that the expansion tank is getting old and leaking a small amount, which probably is why there is vacuum, but not enough to suck back from the overflow tank.
I'll order a new expansion tank and re-post the results. Cheers for all the help so far!
Thread Starter
Racer
Joined: Dec 2003
Posts: 349
Likes: 0
From: Hong Kong
I think it was a tiny tiny leak somewhere in the seams that was pulling air back into the system instead of from the overflow. This dye was a great help, recommended to anyone with the same problem!
Racer
Joined: Mar 2011
Posts: 304
Likes: 0
From: Victoria Australia
The new expansion tank arrived yesterday, installed very easily. This morning, the coolant level in the overflow is back down to the cold mark! hurrah!
I think it was a tiny tiny leak somewhere in the seams that was pulling air back into the system instead of from the overflow. This dye was a great help, recommended to anyone with the same problem!
I think it was a tiny tiny leak somewhere in the seams that was pulling air back into the system instead of from the overflow. This dye was a great help, recommended to anyone with the same problem!
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Lets hope your problem is solved and not bursing from being filled wiht crankcase pressure.
Similar symptoms as you. Leakdown proved nothing
Head gasket leak was temp sensitive so only after XX minutes of driving at XX temp the crack would open up then the motor would get warm overflow a lot etc. Eventually blew the lower hose off one day after I parked it. Was the head gasket. never any moisture in the oil I Could see.
Keep us posted.
Similar symptoms as you. Leakdown proved nothing
Head gasket leak was temp sensitive so only after XX minutes of driving at XX temp the crack would open up then the motor would get warm overflow a lot etc. Eventually blew the lower hose off one day after I parked it. Was the head gasket. never any moisture in the oil I Could see.
Keep us posted.
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Racer
Joined: Mar 2011
Posts: 304
Likes: 0
From: Victoria Australia
Hi Guys,
Finally got my surge tank from the US and installed. Last night I did a 50 mile drive including parking (cooling off) and driving home.
This morning yippee I checked my surge, its dead full and the over flow tank is not filling up. In fact vacuum is working to spec as I filled it a touch under the cap neck line and its above that now. Queue my favorite repair success smilie.
For those of you with 1990-1993 cars, I would seriously check the surge tank if you are noticing coolant filling up at the white over flow tank. Mine was not like dailo's where you could see the leaks. The leak came from the copper fitting where the cap goes on. Between there I can see some green (corrosion for copper) compared to the new one.
Another tell tail, after a drive I use to hear hissing from the cap area and of course this meant when it was cool, it would draw air from there (least path of resistance) than the over flow tank.
I am thinking, with this car getting on to 25 years maybe 17psi (RC-44) is a little too much for the cooling hoses and system. For the LT1's they fitted the 15psi cap (RC27). might change caps to ease pressure.
Finally got my surge tank from the US and installed. Last night I did a 50 mile drive including parking (cooling off) and driving home.
This morning yippee I checked my surge, its dead full and the over flow tank is not filling up. In fact vacuum is working to spec as I filled it a touch under the cap neck line and its above that now. Queue my favorite repair success smilie.
For those of you with 1990-1993 cars, I would seriously check the surge tank if you are noticing coolant filling up at the white over flow tank. Mine was not like dailo's where you could see the leaks. The leak came from the copper fitting where the cap goes on. Between there I can see some green (corrosion for copper) compared to the new one.
Another tell tail, after a drive I use to hear hissing from the cap area and of course this meant when it was cool, it would draw air from there (least path of resistance) than the over flow tank.
I am thinking, with this car getting on to 25 years maybe 17psi (RC-44) is a little too much for the cooling hoses and system. For the LT1's they fitted the 15psi cap (RC27). might change caps to ease pressure.
Racer
Joined: Nov 2005
Posts: 310
Likes: 47
Sounds like the upper tank is not holding pressure. This is not a unusual problem. I replaced the upper tank and cap back on my 1991 in 2005 and things when back to normal. I replaced it even though I could not find anything visually wrong with it but did it anyway as it was the concensus of all the mechanics at the service station that does all my work. Upper tanks are relatively inexpensive.
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 178
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
Just solved this problem on mine. Byaccident with the car hot and running inoticed water dripping from the cap on the radiator. It was coming out the cap instead of going to the overflow tank. Two new caps same problem. Pinched carefully the cap to pull tighter to the radiator. Filled the radiator. No more low coolant light and fluid now goes to and from the overflow. Hope this helps. Good luck.
Intermediate
Joined: Jul 2004
Posts: 44
Likes: 1
Today my sons car overheated and he called me to come and help; and when I arrived on the scene I noticed the overflow bottle's cap had blown off and that seemed to be where the coolant bubbled out from. Perhaps I should replace the radiator cap as a first step?
Thanks all.
Tony
Brick, NJ.
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 178
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
[QUOTE=c4urself;1580573521]I'm sorry, can you reword or rephrase that sentence so that I can really get the meaning of it.. Not too sure what you mean by "pinched carefully the cap. . ."
Today my sons car overheated and he called me to come and help; and when I arrived on the scene I noticed the overflow bottle's cap had blown off and that seemed to be where the coolant bubbled out from. Perhaps I should replace the radiator cap as a first step?
Thanks all.
Tony
Sorry. Took a pliers and squeezed the tabs that pull the cap down tight onto the radiator which put more pressure on the seal. This didn't allow the fluid to blow arround the cap seal. so the fluid had to go to the overflow tank. The cap was flopping around when it was on so the seal to the radiator was not making contact.
If your cap on he overflow blew off your problem is different than I had.
Today my sons car overheated and he called me to come and help; and when I arrived on the scene I noticed the overflow bottle's cap had blown off and that seemed to be where the coolant bubbled out from. Perhaps I should replace the radiator cap as a first step?
Thanks all.
Tony
Sorry. Took a pliers and squeezed the tabs that pull the cap down tight onto the radiator which put more pressure on the seal. This didn't allow the fluid to blow arround the cap seal. so the fluid had to go to the overflow tank. The cap was flopping around when it was on so the seal to the radiator was not making contact.
If your cap on he overflow blew off your problem is different than I had.
Intermediate
Joined: Jul 2004
Posts: 44
Likes: 1
Sorry. Took a pliers and squeezed the tabs that pull the cap down tight onto the radiator which put more pressure on the seal. This didn't allow the fluid to blow arround the cap seal. so the fluid had to go to the overflow tank. The cap was flopping around when it was on so the seal to the radiator was not making contact.
If your cap on he overflow blew off your problem is different than I had.
If your cap on he overflow blew off your problem is different than I had.
Thanks again
Tony
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 178
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
