944: coolant leaking then not leaking

FuelCutOff · 10-22-2009, 03:02 PM

I'd like some help here determining why my coolant leak went away. Car is a 1986 NA 944.

I had the car parked for a weekend. Noticed a wet spot underneath the driver side of the radiator. It was about twice the diameter of a CD...maybe more. I jacked up the car to see where it's from, but couldn't trace the leak. All my hoses were on tight. The leak was from the bottom right of the radiator if facing the car.

About 3 days ago, I stopped the car to fill the coolant reservoir since it was a bit low due to leaking. This was after driving for about 4 miles. Filled it up and went on my way. Since then, I have not noticed any more leaks. What gives?

Not sure if this has anything to do with it, but when refilling the reservoir, I did notice that either air went into the system or escaped as soon as I removed the cap. The motor was moderately warmed up, but not hot enough for me to not remove the cap. I flushed and bled the coolant system about 3 months ago with dextron 50/50 mix. Was the system not properly pressurized, maybe causing the leak?

JohnKoaWood · 10-22-2009, 03:15 PM

Quote:

Originally Posted by FuelCutOff

I'd like some help here determining why my coolant leak went away. Car is a 1986 NA 944.

I had the car parked for a weekend. Noticed a wet spot underneath the driver side of the radiator. It was about twice the diameter of a CD...maybe more. I jacked up the car to see where it's from, but couldn't trace the leak. All my hoses were on tight. The leak was from the bottom right of the radiator if facing the car.

About 3 days ago, I stopped the car to fill the coolant reservoir since it was a bit low due to leaking. This was after driving for about 4 miles. Filled it up and went on my way. Since then, I have not noticed any more leaks. What gives?

Not sure if this has anything to do with it, but when refilling the reservoir, I did notice that either air went into the system or escaped as soon as I removed the cap. The motor was moderately warmed up, but not hot enough for me to not remove the cap. I flushed and bled the coolant system about 3 months ago with dextron 50/50 mix. Was the system not properly pressurized, maybe causing the leak?

My bet is radiator end tank... My N/A did the same thing... leaked on drivers side.. then quit... I found when it leaked was on days when the motor was cold..

Turned out to be the end tank on the drivers side..I replaced with a new radiator and no leaks since... but then I also use GL-9 not dextron...

FuelCutOff · 10-22-2009, 03:21 PM

John, thanks for the reply. I didn't think about the end tank being the problem. Makes sense that's it's leaking somewhere behind the radiator where I can't see it. Still weird how it just went away. Now the leak did happen over a pretty cold weekend, but it's been much warmer lately, so I'm wondering if outside temp is affecting this any. I'll find out when it gets cold again.

krystar · 10-22-2009, 03:24 PM

try a coolant uv dye and light it up with a uv light

GTSilver944 · 10-22-2009, 03:25 PM

Pull the rad fans (disconnect the two wire connectors and remove the 6 screw) and check the small top hose that connects to the overflow tank. Mine was leaking randomly when this hose wasn't tight enough. It seemed to only leak when I drove the car long enough for it to get pretty hot.

V2Rocket_aka944 · 10-22-2009, 03:32 PM

drain plug loose?

JohnKoaWood · 10-22-2009, 04:10 PM

Quote:

Originally Posted by FuelCutOff

John, thanks for the reply. I didn't think about the end tank being the problem. Makes sense that's it's leaking somewhere behind the radiator where I can't see it. Still weird how it just went away. Now the leak did happen over a pretty cold weekend, but it's been much warmer lately, so I'm wondering if outside temp is affecting this any. I'll find out when it gets cold again.

cold weather makes the old rubber seal shrink between the radiator core and the end tank...some radiator shops will repair this, others will not touch it..

my advice..if you pull the radiator and try to get a radiator shop to reseal the end tanks, tell them it is out of a VW, not a porsche... just my advice though...

Mike C. · 10-22-2009, 08:47 PM

Maybe the radiators are improved on the later cars. I went through 3 OEM radiators in a 10 year period. They all failed from cracks in the plastic end caps right at the flange where the aluminum crimps over. The only way to repair this is to find someone who can get new end caps and gasket and re-crimp. Maybe they are available now... they weren't back then (circa mid 90's). Hopefully it is only a loose clamp or leaky fan switch gasket.

FuelCutOff · 10-23-2009, 04:33 PM

Much thanks for the info and advice guys. I really appreciate the help. It looks like there is no other way but to take the darn thing off and inspect it.

951Tom · 10-24-2009, 10:09 AM

Test the system with a pressure tester and you'll be able to quickly find the leak.

bearone · 10-24-2009, 10:56 AM

when you drove the 4 miles the system pressurized, when you opened the cap it vented to atmosphere.

if the leak went away, worry about it when it leaks again but you might try suggestion #10 for some piece of mind.

ernie9468 · 10-24-2009, 12:03 PM

+ 1 GT SILVER I to had a small leak kept trying to find it was hard to spot since they is so much stuff in the way but that where it was leaking from, while your there check around your (thermo fan switche) good luck finding that leak.

10-22-2009, 03:02 PM	#1
FuelCutOff User Join Date: May 2009 Location: Livonia, MI Posts: 19	944: coolant leaking then not leaking I'd like some help here determining why my coolant leak went away. Car is a 1986 NA 944. I had the car parked for a weekend. Noticed a wet spot underneath the driver side of the radiator. It was about twice the diameter of a CD...maybe more. I jacked up the car to see where it's from, but couldn't trace the leak. All my hoses were on tight. The leak was from the bottom right of the radiator if facing the car. About 3 days ago, I stopped the car to fill the coolant reservoir since it was a bit low due to leaking. This was after driving for about 4 miles. Filled it up and went on my way. Since then, I have not noticed any more leaks. What gives? Not sure if this has anything to do with it, but when refilling the reservoir, I did notice that either air went into the system or escaped as soon as I removed the cap. The motor was moderately warmed up, but not hot enough for me to not remove the cap. I flushed and bled the coolant system about 3 months ago with dextron 50/50 mix. Was the system not properly pressurized, maybe causing the leak?

10-22-2009, 03:21 PM	#3
FuelCutOff User Join Date: May 2009 Location: Livonia, MI Posts: 19	John, thanks for the reply. I didn't think about the end tank being the problem. Makes sense that's it's leaking somewhere behind the radiator where I can't see it. Still weird how it just went away. Now the leak did happen over a pretty cold weekend, but it's been much warmer lately, so I'm wondering if outside temp is affecting this any. I'll find out when it gets cold again.

10-22-2009, 03:24 PM	#4
krystar Addict Rennlist Member Join Date: Oct 2007 Location: Schaumburg, IL Posts: 2,182	try a coolant uv dye and light it up with a uv light

10-22-2009, 03:25 PM	#5
GTSilver944 User Join Date: Dec 2006 Location: Denver, CO Posts: 495	Pull the rad fans (disconnect the two wire connectors and remove the 6 screw) and check the small top hose that connects to the overflow tank. Mine was leaking randomly when this hose wasn't tight enough. It seemed to only leak when I drove the car long enough for it to get pretty hot.

10-22-2009, 08:47 PM	#8
Mike C. Super User Join Date: Aug 2002 Location: Eastern CT Posts: 2,664	Maybe the radiators are improved on the later cars. I went through 3 OEM radiators in a 10 year period. They all failed from cracks in the plastic end caps right at the flange where the aluminum crimps over. The only way to repair this is to find someone who can get new end caps and gasket and re-crimp. Maybe they are available now... they weren't back then (circa mid 90's). Hopefully it is only a loose clamp or leaky fan switch gasket.

10-23-2009, 04:33 PM	#9
FuelCutOff User Join Date: May 2009 Location: Livonia, MI Posts: 19	Much thanks for the info and advice guys. I really appreciate the help. It looks like there is no other way but to take the darn thing off and inspect it.

10-24-2009, 10:09 AM	#10
951Tom Addict Rennlist Member Join Date: Oct 2001 Location: Maryland Posts: 1,123	Test the system with a pressure tester and you'll be able to quickly find the leak. __________________ 951Tom '87 951 '01 330ci

10-24-2009, 10:56 AM	#11
bearone User Join Date: Jun 2003 Location: Phoenix, Az Posts: 1,842	when you drove the 4 miles the system pressurized, when you opened the cap it vented to atmosphere. if the leak went away, worry about it when it leaks again but you might try suggestion #10 for some piece of mind.

10-24-2009, 12:03 PM	#12
ernie9468 Addict Rennlist Member Join Date: Jul 2009 Location: caraquet, new-brunswick, canada Posts: 510	+ 1 GT SILVER I to had a small leak kept trying to find it was hard to spot since they is so much stuff in the way but that where it was leaking from, while your there check around your (thermo fan switche) good luck finding that leak.