Pressure in radiator hoses

[Chris1Roll]

You need to get OP to squeeze yours, then squeeze his, and decide which is harder.

[Casheye]

Originally Posted by Chris1Roll

You need to get OP to squeeze yours, then squeeze his, and decide which is harder.

I'm down for some pipe squeezin' I've got family in Stoke so the next time I'm up your way I'll let you know to get your engine warmed up

[Casheye]

Just a quick update;

So after not having had much time to mess around with this car I've ordered a new expansion bottle (which came with the lower pressure cap - 11psi) to fit at a later date and in the mean time, I've drilled and tapped a pressure gauge I had lying around into the side of the existing bottle.

I let the car get up to temp while idling and the pressure increased but only in line with what you'd expect from the coolant getting hot. Then I took it for drive up the ring road and gave it some beans, when I got back to the workshop the hoses were very firm (both top and bottom) and the gauge was reading at 1bar / 14psi.

I didn't have time to take it out again to see if it would increase further but I might have some time today to give it a drive.

The pressure dies right off after the engine is left to cool down and there is no apparent lost in coolant.



I know with the original volvo 22psi cap, there's still some way to go before the car his release pressure but does anyone know if there are any figures for what pressure the cooling system should be running at?

[Rversteeg]

The cooling system is basically a closed system. Under normal circumstances no air or coolant can either get in or out. That means that after the system has cooled down, there should by no under/overpressure left. If there is overpressure, exhaust gass has probably been blown in the system.

Looking at the pressure gauge, your system is working as it should.

[Forrest]

I would agree that 14psi does not sound excessive, although this will vary with ambient temperature and driving conditions.

From a recent post I made in another thread, the following pressure caps are available:

grey = 150 kPa (22 psi) superseded by the green cap
green = 150 kPa (22 psi) standard issue for all 700/900s
white = 100 kPa (15 psi) uncommon
black = 75 kPa (11 psi) standard issue for 140/240s
yellow = 50kPA (7psi) intended for industrial plant.

Change to a black cap and your coolant pressure won't exceed 11psi. However, this will also reduce its boiling point and likely cause your car to overheat under certain conditions.

I would only start to worry about a situation like yours if my coolant were routinely exceeding the 22psi limit the manufacturer intended. I replace my coolant periodically with fresh and flush the system. This all helps to keep it working efficiently.

[230ina245]

"From a recent post I made in another thread, the following pressure caps are available:

grey = 150 kPa (22 psi) superseded by the green cap
green = 150 kPa (22 psi) standard issue for all 700/900s
white = 100 kPa (15 psi) uncommon
black = 75 kPa (11 psi) standard issue for 140/240s
yellow = 50kPA (7psi) intended for industrial plant. "

Why the difference between 140/240's and 700/900's?
Tim

[Forrest]

Most of that information comes straight from the FAQ with the exception of the yellow cap which I included for completeness.

I think Volvo started using the higher pressure grey/green cap on later Turbo cars, presumably to increase the boiling point of the coolant in response to greater heat output from the Turbo. Because the earlier 140/240 systems were not designed for the higher pressure the new, high-pressure caps are not backwards compatible. Apparently, using one on a 240 can damage the radiator. People do swap to the black cap on 940s to mask problems in their cooling system. If you keep the cooling system properly maintained you should have no difficulty using the cap Volvo intended.

The coolant reservoir and cap are on the side from which the pump draws coolant, so the pressure could get a bit higher on the downstream side of the pump.

[baggy798]

To mask inadequacies in the cooling system? To improve emissions? To improve efficiency?

Looks like the 240 atcc cars ran the white cap...

https://www.youtube.com/watch?v=tJuVsW0r50A