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Performing a Coolant Pressure Check on an '84 Diesel Rabbit

I've got an '84 diesel Rabbit. The radiator doesn't have a cap on it. The expansion tank is where you fill/top off the coolant. Now, I've got a small coolant leak that I need to track down. I just had the head gasket replaced in January, so I'm pretty confident that the source of my coolant leak is either the expansion tank, hoses, or radiator. The leak isn't big enough though that I ever see it leaking. I can usally get away with topping off once a month.

According to the Bentley manual, the way to work through this problem is by doing a coolant pressure check. Essentially, you hook up the pressure check device to the cooling system, pump up the pressure, and then watch it to see if the pressure goes down over the next few minutes. If it does, you have a leak. Apparently, when the system is under pressure, it will also be easier to find the source of the leak.

However, all of the pressure check devices I've found so far, attach directly to the radiator fill cap (which I don't have). Does anybody know if these devices can also be connected to the expansion tank? If not, can anybody point me to a source that sells such a device that will work with my particual Rabbit?

Thanks, Bryan

Reply to
Bryan K. Walton
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There are adapters for that (somewhat unusual!) VW tank! But... Some thoughts:

  1. Don't ever rule out the head or other related gaskets. It can happen that they fail right away for a number of reasons (including improper installation, warped head/block, etc.)
  2. Consider this... Clean the engine well. Very well. Bypass the heater core (it's summer, right?) What happens?
  3. Does the cooling system pressurize really quickly? Like in the first few seconds of running? Does the pressure relieve ever kick in? That is a sign of a leaking head gasket.
  4. You cleaned the engine in #2 above. Now, a few weeks later, carefully look for leaks. Did you knwo that Antifreeze when dryed is not green usually? Look for light brown. Spray water, if that brown turns green, that is where the leak is.
Reply to
PeterD

You can pressurize the system through that little hose going to the expansion valve. Be creative since you could probably use a tire/wheel valve, cut it so it can fit, in that hose and a bicycle pump. ;-) Of course block off the expansion bottle nipple and you can check pressure by using a tire pressure gauge.

Remember that you probably shouldn't be able to put too much pressure in the system since the cap will safely release excess pressure. I have seen bad caps not hold enough pressure.

Geez I just thought of that idea and will have to use it myself? So let me know if it works! lol

Reply to
One out of many daves

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