Excessive pressure in the system after engine overhaul | VAUXHALL

Too much pressure usually indicates a faulty head gasket. Check for oil or exhaust fumes in the coolant.

It's not oil or exhaust gases, I've already tested that, and the head gasket I installed is new, as I said, the engine has all been redone.

The workshop should simply check if there are exhaust gases in the coolant. It's called a CO2 leak test.

Was the head checked for hairline cracks and flatness? Was it correctly installed using guide pins and tightened according to specifications? High pressure usually only builds up on the pistons if they are not sealing correctly.

The head was pressure tested and resurfaced by the reconditioner, new guide pins have also been installed, so I can't explain the overpressure.

Did you have this problem before the engine overhaul as well?

Check the water pump. Water must flow through the thin hose on the expansion tank when the engine is running. Otherwise, bleed the system again properly and check the cap on the expansion tank.

No, before that I only had the problem that it was consuming oil, 1 liter per 500 km.

I did a CO2 test, and it was negative.

How did you do that? When it was cold or warm?

Then it would seem obvious that something went wrong during installation or a defective part was installed. Does it build up pressure even when cold, shortly after starting? I would really remove the head again, replace the gasket again, and have the head X-rayed to be on the safe side.

When warm

Does the cooling fan run when it gets hot? If it doesn't turn on, it will also overheat. As long as you have wind while driving, it's okay, but as soon as you stop, it starts to overheat.

The fan kicks in when the engine reaches temperature while idling. I will bleed the system again.

Typically, every cooling system builds up pressure between 1.2 and 1.8 bar.

Since coolant is incompressible, it cannot decompress when pressure is released. This is only possible with air or exhaust gases in the system.

If venting has been carried out according to the manufacturer's specifications, the problem should not occur unless exhaust gases enter the cooling circuit or the coolant boils.

So first, properly perform and check the basic work. Venting according to manufacturer's specifications today almost always involves filling with negative pressure and, increasingly, using diagnostics to control the venting.

Check CO value, possibly head gasket or crack in the head.

It could also be the valve in the expansion tank cap. If it doesn't open, the pressure will get too high.

Check your water pump, the internal impeller may have come loose. I had that happen before, as these impellers were available in plastic and metal.

The water pump was replaced with the timing belt, so that can be ruled out.