Hi all.
Ive been lurking for a while, picking up tips here and there, but despite the pages and pages that have been written about P38s overheating, Ive not found anyone with my exact problem.... so I open the mystery to the collective wisdom of this forum....!
A bit of background:
The car is a 2000 P38 4.6 V8 with an LPG conversion.
Ive owned the car for about 4 years, and despite various problems with the LPG system which were eventually resolved properly last year, Ive had no major problems until this overheating started.
Probably worth mentioning, I did have a gradual coolant leak that I kept on top of by topping up every couple of days (I was pretty lax about antifreeze though, so it ended up a very weak mix).
I had the car booked in to my local independent garage for an MOT, trying to solve the coolant leak, and some service issues (not a Land Rover specialist, but a very good mechanic IMHO). I could see part of the coolant leak around the throttle housing, so this was due to be fixed....
The evening before my garage-date, the car decided to do a proper overheating number on me all the fluid blowing out of the cap. I topped it up and eventually got home by stopping periodically to let it cool down.
At the garage, the initial diagnosis was a faulty thermostat, so this was changed, along with work on the throttle housing. This throttle housing work does seem to have solved the gradual leak.... (NB dry footwell also), but the car does seem to lack a little power since this work.
Got the car back, a couple of days later, same problem new radiator this time.
A couple of days later, same again - new water pump.
Losing patience, and running out of money, I decided to have a go myself. Ive re-done the thermostat, and re-routed some of the LPG plumbing to reduce the height of the pipework relative to the header tank, and installed a bleed valve on the LPG pipework at a high-spot.
My work seemed to have solved the problem, lasting a week this time, but the old problem has returned. A summary is this:
I suspect it is a circulation problem / airlock, but I cant work out how or why or where or more crucially, how to test or fix.
I suspect some will start suggesting slipped liners.... Ive seen it suggested many times, but Im unsure exactly what the symptoms of that would be? I dont claim to be an expert, but does that fit with being intermittent? Also, how would it explain my cool radiator? I did read only today about a bloke whod had his liners done, then got his car back and it still overheated...!
Sorry for the long post, but Ive tried to be thorough.
Any help, suggestions, or answers gratefully received!! Id especially like opinions about whether the throttle housing work could have anything to do with it.....
Many thanks in advance!
Ive been lurking for a while, picking up tips here and there, but despite the pages and pages that have been written about P38s overheating, Ive not found anyone with my exact problem.... so I open the mystery to the collective wisdom of this forum....!
A bit of background:
The car is a 2000 P38 4.6 V8 with an LPG conversion.
Ive owned the car for about 4 years, and despite various problems with the LPG system which were eventually resolved properly last year, Ive had no major problems until this overheating started.
Probably worth mentioning, I did have a gradual coolant leak that I kept on top of by topping up every couple of days (I was pretty lax about antifreeze though, so it ended up a very weak mix).
I had the car booked in to my local independent garage for an MOT, trying to solve the coolant leak, and some service issues (not a Land Rover specialist, but a very good mechanic IMHO). I could see part of the coolant leak around the throttle housing, so this was due to be fixed....
The evening before my garage-date, the car decided to do a proper overheating number on me all the fluid blowing out of the cap. I topped it up and eventually got home by stopping periodically to let it cool down.
At the garage, the initial diagnosis was a faulty thermostat, so this was changed, along with work on the throttle housing. This throttle housing work does seem to have solved the gradual leak.... (NB dry footwell also), but the car does seem to lack a little power since this work.
Got the car back, a couple of days later, same problem new radiator this time.
A couple of days later, same again - new water pump.
Losing patience, and running out of money, I decided to have a go myself. Ive re-done the thermostat, and re-routed some of the LPG plumbing to reduce the height of the pipework relative to the header tank, and installed a bleed valve on the LPG pipework at a high-spot.
My work seemed to have solved the problem, lasting a week this time, but the old problem has returned. A summary is this:
- Ive tried my best to bleed the system completely, but I cant be certain...
- New radiator.
- Two new thermostats.
- New water pump.
- New pressure cap.
- Problem seems to be intermittent.
- Top hose pressure seems ok until I get to the point where the coolant is boiling over then it is very hot and very firm.
- Bleed pipe from top of radiator isnt blocked.
- It has got worse since the work on the throttle housing... coincidence...?
- Power seems down slightly since the work on the throttle housing.
- Coolant has been tested negative for combustion gasses, though I have to say, the fault never appeared whilst the car was in the garage (typical!)
- The overheating only seems to occur when the car is travelling rather than being stood on tickover.
- No sludge in oil.
- No obvious oil in coolant.
- It has spent a lot of time over the last few months with a very weak mix of antifreeze.
- Usually, when it is overheating, the middle of the radiator is cool.
- Passenger footwell is dry.
- Im in the UK. Weather not particularly warm or cold, and doesnt seem to be a factor either way.
- Even when the car has been behaving over the last week or so, when looking under the bonnet immediately after going for a drive, the pressure cap has been hissing gently releasing gas.
- I cant think of anything else.
I suspect it is a circulation problem / airlock, but I cant work out how or why or where or more crucially, how to test or fix.
I suspect some will start suggesting slipped liners.... Ive seen it suggested many times, but Im unsure exactly what the symptoms of that would be? I dont claim to be an expert, but does that fit with being intermittent? Also, how would it explain my cool radiator? I did read only today about a bloke whod had his liners done, then got his car back and it still overheated...!
Sorry for the long post, but Ive tried to be thorough.
Any help, suggestions, or answers gratefully received!! Id especially like opinions about whether the throttle housing work could have anything to do with it.....
Many thanks in advance!
