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1995-2002 Range Rover P38A
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Discussion Starter #1
My 97 P38 4.6 has blown another (genuine) coolant header tank. This is the third I have had in the last 5 years. First was a fracture around the throttle heater return pipe connection, second was a fracture in the back wall of the tank, third was three fractures on the top half, and now a split where the neck joins the body. The temp gauge has also shown signs of rises in temperature when stick in traffic in the last month, and the latest was a week ago where the temperature went up while I was in traffic but didn’t stabilise when I got onto the highway. When I looked under the hood, there was a hissing and fine mist coming from the header tank neck, and coolant dripping on the floor from around the thermostat area. Couldn’t get under the car to look as I was wearing my suit. I suspect this is down to over-pressure in the cooling circuit, and may be the reason for my history of fractured tanks. I thought the header tank cap had a pressure release valve.

So, on Sunday I took the thermal camera from work and got the car up to normal temperature. These are the images of the radiator looking from the engine towards the front. Looks very cooler towards the bottom centre. Blockage in the rad perhaps?
 

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JACK'S GRANDAD
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Looks like the radiator is doing it's job to me.
As far as pressure goes, it can only make it one way really. So not understanding you blaming a thermostat for the blown tanks? Or was I reading that wrong?
Ever done a sniffer test on the coolant tank?

Martin
 

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1995-2002 Range Rover P38A
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Discussion Starter #3
Hi Martin. No, I wasn't blaming the thermostat, just noticed coolant leaking from around that area, as well as the neck of the header tank. I thought the pressure may be so high it was leaking form somewhere around the stat. Engine sounds fine, and no abnormal sound when I start, which I believe is a sign of gasket or liner. Am I correct that the cap on the header tank has a pressure release??

Here's an image of the plumbing from the header tank

. FLIR0036.jpg
 

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A sniffer test is a kit you purchase at the auto parts store to see if you have exhaust gasses in your coolant.

Yes the cap controls the pressure in the system. Cheap to replace if you question it at all.
 

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When you say header tank, I'm assuming you are actually referring to the expansion tank. Expansion tank cap does have a pressure release function. It's possible that the cap is malfunctioning, or the wrong spec cap has been installed in the past. I believe the correct pressure setting for our expansion tank cap is 140 psi.
 

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I believe the correct pressure setting for our expansion tank cap is 140 psi.
You believe wrong, it's 1.4 bar or around 20 psi. 140 psi would burst every coolant hose on the car and probably pop the top cap off the radiator too. The pressure cap is the same as a 5 series BMW of similar vintage to the P38 so easy to get hold of.
 

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I suspect your cooling system needs some TLC & diagnosis (not diagnostics).

First bleed the system properly according to RAVE procedure.
Second check the pressure cap is not blocked or rusted up.
Third do a proper pressure test using a gauge (i.e. no more than 20 PSI as above).
Fourth, bleed the remaining air out you missed last time.

Also where are you getting the header tanks from ? I had some issues with Leyland Rover tanks many years ago, but these were nothing to do with LR.
 

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1995-2002 Range Rover P38A
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Discussion Starter #8
The header tanks are genuine Land Rover and coming from Brit Car. The cap was replaced a couple of years ago.
The system has been bled when I last changed the header tank, and all was well. I also bled is last weekend when running the car up to temperature to take the thermal images. I'll get my local to do a sniff test and take it from there. Oddly, when running it up to temperature at the weekend, the temp was normal, no escaping coolant from the neck of the tank. Seems to be intermittent, as with so many things on the RR. Still love 'em!
 

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JACK'S GRANDAD
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I'd personally lose the fancy camera and replace it with a $50 (over here) head gasket test kit.
Something is pressurizing the coolant system, and that can only really come from one source. Assuming the system can hold the requisite pressure.

Martin
 

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JACK'S GRANDAD
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