Radiator End Cap Leaks Under Pressure
 

I'm wondering if others have had this experience. My wife and daughter took the '96 turbo to the city one hour away. While driving in the city, the car lost coolant on the ground which my daughter promptly noticed and immediately stopped. There was no "low coolant" light, and the temperature gauge breifly spiked. The car was towed home.

The overflow tank was empty, so I filled it and started the car. The radiator showed evidence of fluid leaking along the passenger side endcap. The engine sounded normal and the tank did not empty, nor did I see any leaking fluid. I idled it for a few minutes and shut it off. After sitting for a few days, there is only a small spot under the car.

I suspect the end cap released when the car was hot and the cooling system was pressurized. Now that the pressure is relieved, the cap keeps its seal.

I'm planning to start the car and let it get to operating temperature to verify this.

Has anyone else experienced this?

Is the "end cap" the radiator reservoir cap? If so ck that it's holding pressure with a tester, or just replace it. Sounds like it may not be holding pressure.

The plastic end tanks on the radiator is what I mean. I didn't even think about the overflow cap - perhaps that's my problem source. Thanks for the tip!

Mine leaked for a long time because the overflow tank's threads for the cap were slightly stripped and it wasn't getting a good seal. The fluid would drip along the line to the thermostat and fall onto the frame of the car, where it would travel and drip somewhere else under the car.

It took me a bit to realize it was the tank, check around the cap for dried up anti-freeze or check the hose coming out the bottom of the tank, if it's leaking that should be COVERED in dried fluid.

Hope this helps, good luck with your leak.

It's the turbo coolant hose on the driver side.

I started the car and let it idle up to operating temperature. As it warmed I noticed bubbles in the small return hose to the overflow tank - head gasket??? Nope - no smoke out the tailpipe and the bubbling subsided. I looked at all the hoses as it warmed.

After running for 10-15 minutes, the temperature remained constant and there were no leaks. So I shut it off - puzzled, but leaving the hood open. Upon returning to the car a few minutes later to shut the hood, I noticed a trail of coolant from the car.

The coolant trail wasn't from the radiator - not even close. I jacked the car up to peer up from below. After placing a jackstand for safety sake, I slid under with flashlight in hand. The coolant was coming from a hose directly above the rear mount. I looked above and below and found radiator and heater hoses intact without leaks. The only hose left was the turbo coolant hose. I had to use a mirror to get a better look.

I found a puffy hose with evidence of leaking! I'm so glad I didn't rush out to buy a new radiator. Instead of $170 for a radiator, it is an $8 hose. It pays to research the source!

Some people really get upset when you tell them you can't diagnose a leak on a forum and they need to get in there and dig. You can give them places to look but that's the problem with a leak. You really do have to get in there and follow the trail. Glad to hear it's only a hose and not the radiator. I replaced that hose a while back as mine was really spongy and looked like it should be leaking !!

Today's radiators are made well and shouldn't leak. Having said this it is one of the weak spots where they take a plastic end cap or tank and crimp the aluminum core to it with a gasket. It is a failure point and as it starts to fail it will leak under pressure and reseal itself as the pressure diminishes. As it gets weaker it will start to leak earlier and earlier until it is leaking with no pressure applied. It was a good guess.

Kiss - I was surprised at what I ultimately found in my 20 minute examination, but relieved.

I recently had an endcap catastrophically fail on another Volvo, ultimately resulting in engine damage because the driver didn't recognize and react in time (interstate driving). I'm a lot skittish about the radiators now.

What Kfrog said!! All the forums in the world can't replace eyes and ears on the ground! :)