Cooling system pressure test

[wigginzoid]

Is it possible to do a coolant pressure test from the reservoir? I havnt found any threads or parts that are compatable with it

[VMRWheels]

You're supposed to do it from the radiator cap, the reservoir was never meant to be pressurized.

[old guy]

Yes you can do it from the reservoir cap. Typically the coolant system pressure is controlled from the radiator cap and the reservoir handles the overflow. However, with the B6 the radiator cap and reservoir cap are incorporated into the same function. Consequently the reservoir is pressurized and the reservoir cap has an overflow that empties underneath the reservoir.

[VMRWheels]

^ ah, I stand corrected!

[wigginzoid]

Yes you can do it from the reservoir cap. Typically the coolant system pressure is controlled from the radiator cap and the reservoir handles the overflow. However, with the B6 the radiator cap and reservoir cap are incorporated into the same function. Consequently the reservoir is pressurized and the reservoir cap has an overflow that empties underneath the reservoir.

Is there a special part that connects to the reservoir?

[old guy]

Is there a special part that connects to the reservoir?

No. the reservoir cap is a pressure release cap just as a pressure release cap you would typically fine on a radiator core. As long as the pressure tester seals on the reservoir you are good to go.

What is the issue you are trying to diagnose?

[wigginzoid]

im not sure if the pressure tester will seal on the reservoir but i'll give it a shot thanks

[wigginzoid]

I have a coolant leak and i can seem to find it.

[old guy]

I have a coolant leak and i can't seem to find it.

Take a close look at the back of your motor. The rear coolant flange is a common source of coolant leakage. Mine started leaking around 100K miles. The coolant runs down the transmission and isn't readily visible from underneath the hood.

[wigginzoid]

already had that replaced last year

[old guy]

Another common leak source is from the radiator end caps. Also, have you removed your belly pan and looked for signs of leakage from the water pump?

[audinaut]

Got Bentley? It calls to pressurize system to 1 bar (14.5 psi) for leak testing using hand pump tool VAG1274 with adapter for cooling system tester VAG1284/8. You don't need those tools to pressure test, but it show's you what the book calls for and maybe give you an idea of how to McGuyver something yourself. In addition to area's Old Guy suggests checking, other known areas of coolant leak are the reservoir tank ends the hoses slip/clamp over and the J-Plug located drivers side of block next to the thermostat.....but leaks in these areas usually drop coolant on the ground and are easily seen/noticed.

[audinaut]

Mine started leaking around 100K miles.

How were you so lucky?!!? It seems more common for people to experience the DIY "joy" of coolant flange replacement just north of 50K.