Coolant Pressure

rangiegal · Sep 3, 2009

I was just wondering what the approx pressure should be when the engine is just warm and the top-up cap is released ? Or when cold - should it still be under pressure? I've noticed there always seems to be pressure there, usually open it when slightly warm though.

All this talk about coolant loss.....I've topped up coolant for the past 5 years on my Rangie, but never known exactly where to top it up to as the overflow tank isn't clearly marked with a level indicator, so I do it to top of the lower half of the plastic overflow tank - the correct level indication would be nice, if anyone is able to help!!

My Rangie has served me well, if a tad expensively, for 5+ years now and I suppose the dreaded liners may slip some time, but I hope its not anytime soon. Heads were redone about 2 years ago and only because there was a slight oil leak from one of them. No sinister signs of oil and coolant mixing and plugs when changed a few weeks ago were burning a good colour. But I've always had to top up coolant, ever since I've had it, every few weeks or so, although not by very much.

I think there may be very gradual loss from an aging radiator, some signs of dried coolant streaks in places. No overheating other than once, years ago, before the heads were redone, when the thermostat stuck.

Your thoughts on this would be appreciated as there is a load of experience here....should I be worrying unduly / ditching the Rangie soon / preparing for the worst or just changing the radiator?? Its a 1999 T reg Vogue 4.6 Special Edition

Datatek · Sep 3, 2009

If it's warm there will be pressure but I would not expect pressure when the engine has fully cooled.

I have always been led to believe that the pressure cap should not normally be removed except when the engine is cold as effectively the pressure in the expansion tank pushes water back to the rad etc as cooling and contraction takes place.

change the rad if there are signs of leaks before it fails and costs you! Then see if you still have to top up.

wammers · Sep 3, 2009

rangiegal said:
I was just wondering what the approx pressure should be when the engine is just warm and the top-up cap is released ? Or when cold - should it still be under pressure? I've noticed there always seems to be pressure there, usually open it when slightly warm though.

All this talk about coolant loss.....I've topped up coolant for the past 5 years on my Rangie, but never known exactly where to top it up to as the overflow tank isn't clearly marked with a level indicator, so I do it to top of the lower half of the plastic overflow tank - the correct level indication would be nice, if anyone is able to help!!

My Rangie has served me well, if a tad expensively, for 5+ years now and I suppose the dreaded liners may slip some time, but I hope its not anytime soon. Heads were redone about 2 years ago and only because there was a slight oil leak from one of them. No sinister signs of oil and coolant mixing and plugs when changed a few weeks ago were burning a good colour. But I've always had to top up coolant, ever since I've had it, every few weeks or so, although not by very much.

I think there may be very gradual loss from an aging radiator, some signs of dried coolant streaks in places. No overheating other than once, years ago, before the heads were redone, when the thermostat stuck.

Your thoughts on this would be appreciated as there is a load of experience here....should I be worrying unduly / ditching the Rangie soon / preparing for the worst or just changing the radiator?? Its a 1999 T reg Vogue 4.6 Special Edition

If you look into the header tank you will see a plastic lip sticking up that is the water level. Any filling above that with engine cold will be expelled from the overflow when engine is hot. Standard cap pressure is usually around 15 psi. Each psi of pressure raises the boiling point of water by 2 degrees so the water will not boil at 212f degrees but at 242f degrees. This allows the engine to run at a more efficient temperature. The cap should never be removed with engine hot and water should never be added unless engine is fully cooled or you will never get the correct level. If you fill with engine warm water level will drop on cooling if you fill with engine cold water level will rise on heating. That is why it is called an expansion tank.

rangiegal · Sep 3, 2009

Thanks for that - will look for the lip in the expansion tank. So the engine should actually be completely cold when topping up the expansion tank?

I think I'll have a new rad fitted as well, the old one is the original and is showing deterioration in places. The car runs very well so I suppose although it may pop its clogs anyway at some stage,if all the posts on this site are a reflection of p38 ownership in general, but a new rad may be a good investment. It never runs hot - always bang on the middle of the temp gauge, but there has been minor coolant loss over the years, perhaps because I have not topped it up when completely cold. :doh:

gavbriggs · Sep 3, 2009

best to top up first thing in the mornin!! (or after you got out of bed if you work feckin nigts like me!) i'm sure there is a level indicator between the wing and the exp tank side of the tank. might be wrong.

mine hasnt lost a drop since i did the block and i'm over the moon with it, prolly blow up later now if you are worried, you could maybe source an engine block(i have 2) and go about getting it top hat linered and rebuilt. you can re assemble it yourself and then in the event of failure you have the block ready!!! thats the only way to combat the liners slipping and to be honest i'm intending doing mine as soon as i get a bit of cash!

Coolant Pressure

rangiegal

New Member

Datatek

Well-Known Member

wammers

No longer with us, RIP

rangiegal

New Member

gavbriggs

Well-Known Member

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