Radiator caps

[ytt105]

I had a problem the other week in the hot weather.

My radiator cap started spewing out litres of coolant. I refilled with water and replaced the cap with one I had on my previous P38. Interesting thing is the one on my 1999 P38 has a figure of 140 on it, presumably the celcius temperature that it opens at, where as the one from my 1996 P38 had the number 200.

I'm going to use the higher numbered one as it performed fine on the drive home towing a van.

Should I or shouldn't I.

Regards
Trev

[Scouse]

Both GEMS & Thor engines share the same cap (ESR1480) so maybe one has had a different spec cap fitted at one stage.
Fitting a higher pressure cap is a risk though as the extra pressure might make something expensive the fuse.

Factory spec is 1.0bar or 15psi.

[PeterAllen]

Just checked on mine and there isnt a number on the cap...so cant help you

[mtb_gary]

Both GEMS & Thor engines share the same cap (ESR1480) so maybe one has had a different spec cap fitted at one stage.
Fitting a higher pressure cap is a risk though as the extra pressure might make something expensive the fuse.

Factory spec is 1.0bar or 15psi.

Scouse, sorry to disagree with you but according to the RAVE manual:


The tank is fitted with a sealed pressure cap. The cap
contains a pressure relief valve which opens to allow
excessive pressure and coolant to vent through the
overflow pipe. The relief valve opens at a pressure of
1.4 bar (20 lbf.in) and above.

Gary

[PeterH]

Have a close look at your cap, there should be two o rings, see attached photo of my old and new caps. On the left is the new one with both seals present, on the right is the old one, you can see the end has preished with heat and age, allowing the o ring fall into the expansion tank. I was able to fish out the old o ring which was sitting in the tank. This could cause coolant loss, I'm sure both o rings are there for a reason.
Cheers, Pete.

[Scouse]

Scouse, sorry to disagree with you but according to the RAVE manual:


The tank is fitted with a sealed pressure cap. The cap
contains a pressure relief valve which opens to allow
excessive pressure and coolant to vent through the
overflow pipe. The relief valve opens at a pressure of
1.4 bar (20 lbf.in) and above.

Gary
I'm quoting figures from TOPIx:

COOLING SYSTEM - V8 ENGINE

System type Pressurized, spill return, thermostatically controlled water and anti freeze mixture. Vertical flow radiator with remote header tank and pump assisted.

Cooling fan 9 blade axial flow. Viscous coupling.

Pump type Centrifugal, impeller, belt driven.

Thermostat opening
Up to 99MY 88 C 190 F
From 99MY 85.5 C 185.9 F

Expansion tank cap pressure (system pressure) 1.0 bar 15 lbf/in

[mtb_gary]

Scouse

What if we split the difference and go with 1.2bar :confused:. BTW, I checked my cap this morning 140. I'm wondering if somewhere along the way a Land Rover tech bulletin may have changed recommended specification to 1.0 bar?

Gary

[PeterAllen]

Thanks Peter, My cap looks the same as your old one and no sign of the first O ring. It too is marked 140.
Having a good look at the cap end and the top of the expansion tank I can't see how the O ring would be able to seal against the tank in any event. The O ring is too small a diameter to meet with the sides of the tank. I note these caps are used in a number of other vehicles e.g.BMW and maybe for a different set up although I admit I have no ides how the cap actually works when excessive pressure is applied so may have nothing to do with sealing against the side.

[Scouse]

Scouse

What if we split the difference and go with 1.2bar :confused:. BTW, I checked my cap this morning 140. I'm wondering if somewhere along the way a Land Rover tech bulletin may have changed recommended specification to 1.0 bar?

GaryI wonder which is right, 5psi difference is quite a bit.

[mtb_gary]

What about a quick survey of P38a's?

Whilst your car is cold can you remove the radiator cap from the expansion tank and check what number is on it. As Scouse highlighted the 5 psi is a big difference!

Gary

[ytt105]

Well, as originally posted I have both 140 and 200!

I'm still presuming these numbers represent Celsius degrees, but how does that relate to pressure?

[ytt105]

I may have answered my own question.

140 probably means 140 kpa which is 20 psi which is 1.37 bar
200 kpa 29 psi 1.99 bar

So it seems every one is right!

But, I still don't know which one I should use!

[mtb_gary]

ytt105,
personally I'd steer clear of the 200 and have a maximum of 140 as per RAVE manual. As you've probably noticed Scouse has the TOPIx manual at 100. So 200, IMO is going to be putting too much pressure in the cooling system and potentially causing additional problems.
Gary

[FiveSPDDisco]

For what it's worth all the new caps we get are marked 140

[Hoges]

Cap is several yrs old... 140

[PaulP38a]

I bought several new genuine caps from the UK as spares. They are all marked as 140.

[ytt105]

Ok OK !!!

I've put the 140 one back on, after replacing the O rings just for the hell of it.

I'm now starting to check the fan coupling, its the only part I haven't replaced.

My son just 'refurbished' his coupling by replacing the oil inside. He says it definitely works, but it was on a Nissan GQ (Maverick actually) so will it work on the P38.

Trev

[Craig_Keira]

Trev, are you actually overheating? Or did the cap simply let go?

Today would have been a good test :)

[ytt105]

Craig, it got hot and spewed half the coolant out the radiator cap. Thats when I found my 'spare' cap was 200, not 140 like everyone elses.

Im getting paranoid now watching the temp monitor all the time, but all seems to be OK.

Just a bit worried about the fan coupling, will have to keep an eye on it.

[Hoges]

Sounds to me like you've got pressure building in the coolant system... either an air bubble or head gasket leak. Have have you had it checked for exhaust gases...?

[benji]

I think it could have been your cap that caused it to overheat. If a cooling system can't hold pressure it'll allow the engine to overheat.

For the record mine says 140 too.

[glenhendry]

My old and new ones both say 140.

PeterH, I had the same issue as you with a missing oring on the overflow cap!

[DT-P38]

Off the old or new one?

[BusinessConnected]

I had issues with my Radiator Cap not sealing correctly... Vehicle was overheating on Warm Days...

I replaced the Expansion Tank & Cap (Came as a Complete Set) about 3 weeks ago... Had Melbourne's 9 Days of 30+ including a Trip to Yarrawonga (40 Degrees) no issues...

Purchased from Ebay for $100 Shipped....
Land Rover Radiator Expansion Tank Reservoir Cap Discovery 2 II Range P38 Allm | eBay (http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&vxp=mtr&item=181099670110)

[trout1105]

I have recently had overheating issues with my D2a V8.
I have replaced the bottom hoses because the heater outlet was broken on that plastic 3 way gizmo and I thought that that was the end of it.
It is still overheating so I checked the thermostat and that is just fine (2 yeas old) but I did notice that my expansion tank cap had some damage to it and the top "O" ring wouldn't be seating properly.
I will head into town tomorrow to pick up a new cap and hopefully this will resolve the overheating issue [bighmmm]

Here is the damaged cap.
129860129861

[TheTree]

I only use genuine radiator caps becuase I have had all sort of pressure problems with after market ones!

Steve