Coolant pressure test 1994 MB SL 3.2

[PositronicRay]

I had a problem with a coolant leak, coolant was pooling under the car from the bulkhead drain. prime suspect heater valve and coolant recirculation pump. These are very awkward to get at and observe, by the bulkhead and under the brake servo.

I replaced both anyway, the heater valve used to stick a bit and the recirc pump wasn't working. I couldn't see any tell-tale signs of leakage, just one rusty screw on bottom the inop recirc pump.

All seems to be okay, 30 mile drive no apparent leaks, I carried out a hot pressure test, no hissing or coolant leaking.

Normally I'd just leave it at that and keep an eye on it. But I'm due to be doing a 2000 mile trip in the next few days, I'd like to be 100% sure it's fixed.

So my plan, hook up my pressure tester (I use an old foot pump with gauge) put a nominal 5psi in with the engine cold. Run the engine up to temp, leave overnight to get cold again, and in the morning I should still have a nominal 5psi. Right?

The workshop manual states a pressure test should only be carried out HOT on this engine, due to the head gasket not sealing until up to temp. Otherwise I'd just put 15psi in cold and expect it to hold pressure for a few hours.

Or am I over thinking the whole thing and just paranoid?

[stevieturbo]

Run the engine til warm, them pressurise the system.

Leave the cap off until warm if need be.

Test to ensure it holds pressure, 5, 10, 15psi whatever suits.

Testing cold is sort of pointless, and pressurising cold, running and expecting it to come back to same pressure again....I doubt it.

[PositronicRay]

Thanks

[PositronicRay]

I put 14 psi in, pressure held for 15mins, after 20 maybe 1 psi lost. Probably due to the engine cooling down, I'm thinking that's ok. Right?

[stevieturbo]

Dont think I'd worry too much about that

[PositronicRay]

Thanks, I'll put a spare bottle of coolant in the boot. Just in case.