84 300 SD radiator pressure test
 

I had a leak in my coolant system and it seemed to be coming from the gasket behind the water pump housing. To make a long story short, I replaced the suspicious gasket and the water pump (and its gasket) after taking the housing off.

Now I am trying to do a pressure test before I refill the system. I cannot find the pressure I should pump the system up to and I am searching for it. Does anyone know offhand? Even at 5 psi I saw a leak previously, so that pressure may suffice, but I don't want to overpressurize and cause some more damage...

Thank you

the radiator cap will have a pressure marked on it [measured in atmospheres] this is the pressure not to exceed[approx 14.5psi].

radiator cap
 

Thank you, David. I did not see a # listed on the cap (which was all in German..) but I will look again and go with your # for the test. Thank you!

Dan

pressure test ct'd
 

I pumped up the system to 10 psi and observed a hairline leak in the auxiliary reservoir. My question is, is it reasonable for me to drive before fixing it?

I did use RTV blue to coat the region of the hairline (which is along the central ridge that separates the upper and lower halves). I question whether that will seal it, but am letting it cure before I retest it. I have a road trip next week and would really like to take the Merc. My other leaks seem to be resolved at this point (and they were more like at 5 psi and from the gaskets).

I am really glad I bought this radiator pressure tester. Its really helpful to see where I have leaks before filling the radiator system!

That's not exactly true. The bar/psi stamp on the cap is the opening pressure of that cap, not a "do not exceed" pressure for testing.

Just about any cooling system should be able to hold at least 25lbs for 30 minutes without dropping.

I would be very reluctant to exceed the rating on the cap. There are a lot of components in the cooling system that would probably survive just fine for many more years without entering into what seems the danger zone. Heater core and cylinder head gaskets come to mind. The cap should open at it's rating. Why exceed the normal presure looking for a leak?