Stored Pressure in the Cooling System...??

Just been down to the L322 to look for something and noticed a small pool under it again.....now, before you all go ego, trumps and have coronaries, it is not totally *bad* news....

Opened bonnet and the expansion tank top was stained and there was a small pool of coolant under the cap...strange, it hasn't been driven for about a day and a half!!

Opened the cap and it pee'd coolant all over the place - massive over pressure.....

Now, this means the cooling system is leak free as it held the pressure for 36 hours which is the good news, so that eliminates the hoses, joints, rad, heater matrix, valley gasket, heater manifold and pipes, heater valves, LPG vapouriser hoses, gear box oil cooler and the alternator housing.....

But it also shouldn't do it either!!

Now, considering there is no white smoke and she runs a dream, no MPG variances, oddles of power, no lumpy idle, no getting overly hot (apart from on hols as per previous thread) and no oil/water mix....could it be the expansion tank cap failing closed and not controlling the pressure in the system...or do they tend to only fail open and not closed??

Will get a new one anyway, but wanted to hear your thoughts...not only on the cap, but on your thoughts on the current over pressure issue....

(please can we not de-generate this into a L322/P38 battle nor an attack on the L322 in general....that is getting a bit old now, agree to disagree and enjoy whatever Range Rover you choose to drive......unless it is an Evoque or an Underpigeon, then we reserve the right to right royally take the p!$$ out of you! )

Saint.V8 said:

agree to disagree and enjoy whatever Range Rover you choose to drive......unless it is an Evoque or an Underpigeon, then we reserve the right to right royally take the p!$$ out of you! )

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:focus:

ant in all fairness this prob has only appeared since you installed the new rad,is it poss faulty ? but on the other hand your old rad was leaking which obviously would mask any over pressure problems.even though you say everthing appears fine I would be looking at the weakest link the LPG system it only takes a trickle leak into the water system via the vaporiser,had it go the other way on my d2 trickles of water in the lpg & it wiped out all 8 lpg injectors,obviously try a new cap first.

Only thing that can force coolant out like that is air pressure. You may have a problem Ant. Do you know anybody with a static test rig?

wil2813 said:

:focus:

ant in all fairness this prob has only appeared since you installed the new rad,is it poss faulty ? but on the other hand your old rad was leaking which obviously would mask any over pressure problems.even though you say everthing appears fine I would be looking at the weakest link the LPG system it only takes a trickle leak into the water system via the vaporiser,had it go the other way on my d2 trickles of water in the lpg & it wiped out all 8 lpg injectors,obviously try a new cap first.

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Cheers Will,

Going to be thinking about unplumbing the coolant hoses from the vap and join together and run without LPG for a couple of journeys and see what happens.

Keith did mention it may be the vap when I had the original over pressure but LPG MPG is still rock solid so not losing any as far as I can tell, but yer never know!

Also looking to see if I can get hold of BT500 Block Tester kit and do a sniff test on the coolant, also check the radiator bleed/overflow pipe as I have heard this can cause issues if blocked.

As you say, seems strange it has happened since the rad change, but you are also right that the rad leak could have either masked the problem or even be a result of it!

Will try new cap, Run with no LPG for a few days (oh my poor bank balance running on petrol!!) and try and get a sniff test either done or get my own!

wammers said:

Only thing that can force coolant out like that is air pressure. You may have a problem Ant. Do you know anybody with a static test rig?

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Unfortunately I don't Tony....

If it holds pressure as it has done for 36 hours, what further information would a static pressure test give??

Saint.V8 said:

Cheers Will,

Going to be thinking about unplumbing the coolant hoses from the vap and join together and run without LPG for a couple of journeys and see what happens.

Keith did mention it may be the vap when I had the original over pressure but LPG MPG is still rock solid so not losing any as far as I can tell, but yer never know!

Also looking to see if I can get hold of BT500 Block Tester kit and do a sniff test on the coolant, also check the radiator bleed/overflow pipe as I have heard this can cause issues if blocked.

As you say, seems strange it has happened since the rad change, but you are also right that the rad leak could have either masked the problem or even be a result of it!

Will try new cap, Run with no LPG for a few days (oh my poor bank balance running on petrol!!) and try and get a sniff test either done or get my own!

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ant bear in mind its stood 36 hrs the water pressure should naturally go down easy overnight.but on the otherhand theres always a 90-100 ltr pressurised cylinder sitting in the spare wheel well wanting to escape
can you smell even the faintest of lpg in header tank?

wil2813 said:

ant bear in mind its stood 3 days the water pressure should naturally go down easy overnight.but on the otherhand theres always a 90-100 ltr pressurised cylinder sitting in the spare wheel well wanting to escape
can you smell even the faintest of lpg in header tank?

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There is an odd whiff to the coolant, and considering it is fairly new coolant, I would have thought it would have the sweet smell to it, and this is a bit musky I have to say....

I do think you are right as (although it was 30 - 36 hours as girlfriend drove it yesterday mid morning) it should have dissipated by now!!)

Will unplumb and see what happens, then go for an LPG service if it behaves!

Saint.V8 said:

Unfortunately I don't Tony....

If it holds pressure as it has done for 36 hours, what further information would a static pressure test give??

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It would show you a build of pressure over and above normal as the engine runs. Pressure build should be gradual as coolant heats. A rapid build of pressure would tell you a story. High pressure gas will flow through an aperture that coolant won't.

could it be engine pressure head gasket or cracked head you can get a test for coolant contamination at most garages?

My first thoughts where the vaporiser as previous suggestions but that said the LPG tank should be isolated with the ignition off so it maybe a good idea to check if your getting seepage from the shutoff Valve on the tank.

I had a problem with the coolant cap - it ended up that I hadn't bled the coolant tank ( the cross headed screw next to the fill), this produced a weep around the cap. I think this is similar to the P38 rad bleed hose - in that this should be blown through to stop an airlock?
As an aside, my coolant tank actually split, a symptom I have yet to find the cause for, as the new one is absolutly fine.