P38A 4.6 V8 MY2000 overheating. Intermittent

Hi Andy,

Did you drain from the block or just whip off bottom hose? How much came out on first drain?

andymalham said:

Update. Still getting a lot of bubbles back into the expansion tank even when cold. Coolant stinks of exhaust fumes. I have just put some K Seal in and took it out for a short drive. Seemed OK. radiator warmed up and the LPG switched over and stayed switched on. Will take it out for a longer run tomorrow. Our local LR specialist says that porous liners is a common problem and that K Seal works about 60% of the time. Fingers crossed.

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blocks crack behind the liners and when hot gasses can escape down behind liner into coolant

biketeacherdave said:

you mite just be air locked at the stat very common

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I have had that, no end of hassles.......

Falk said:

Hi Andy,

Did you drain from the block or just whip off bottom hose? How much came out on first drain?

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Just the bottom hose. Don't know how much came out. Didn't measure it.

jamesmartin said:

blocks crack behind the liners and when hot gasses can escape down behind liner into coolant

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I don't think the K Seal worked although I am going to take it out for another gentle run today just to be sure.
If I do decide to take it to the next level i.e. repair, is there anyone you would recommend from personal experience that could supply a replacement engine with all the mods done correctly? I would expect a recon engine to have new pistons, valves, valve guides, seats recut, etc, etc and not just an old engine that has been steam cleaned to make it look good.
Although we are a motorcycle repairer we have the skills and equipment to change an engine.

Ok. If it was me I would drain the coolant from the block and reflush. i would agree with most on here saying you have an airlock, causing hot spots in the block. By pass the stat (I would just get some spare hose and connect in place - a stat is only for decreased warm up time so no adverse effect)

It would also be worth pressure testing your system. The rating should be on the expansion tank cap, or on rave. If you are getting a reading that is dropping away you have coolant loss in the system (sorry for pointing out the obvious!), or of it is fluctuating then air lock is possible. All my own opinion, before some one jumps all over it !

andymalham said:

I don't think the K Seal worked although I am going to take it out for another gentle run today just to be sure.
If I do decide to take it to the next level i.e. repair, is there anyone you would recommend from personal experience that could supply a replacement engine with all the mods done correctly? I would expect a recon engine to have new pistons, valves, valve guides, seats recut, etc, etc and not just an old engine that has been steam cleaned to make it look good.
Although we are a motorcycle repairer we have the skills and equipment to change an engine.

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If it is a cracked block / liner. I would suggest either getting your existing block top hat linered or buy a new top hat short engine. Check out Turners / V8 Developments. Not cheap though!

martynv8 said:

If it is a cracked block / liner. I would suggest either getting your existing block top hat linered or buy a new top hat short engine. Check out Turners / V8 Developments. Not cheap though!

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Seen a Turner engine for sale at £1195. Very Tempted. No cyl heads but mine have been skimmed and pressure tested so I am pretty confident they are OK

Falk said:

Ok. If it was me I would drain the coolant from the block and reflush. i would agree with most on here saying you have an airlock, causing hot spots in the block. By pass the stat (I would just get some spare hose and connect in place - a stat is only for decreased warm up time so no adverse effect)

It would also be worth pressure testing your system. The rating should be on the expansion tank cap, or on rave. If you are getting a reading that is dropping away you have coolant loss in the system (sorry for pointing out the obvious!), or of it is fluctuating then air lock is possible. All my own opinion, before some one jumps all over it !

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I ran with a stat that had failed open (effectively bypassing it) for ages. When hot it only just got out of the blue zone. Ran fine though, no issues at all. I almost prefer it as these things run way too hot in my opinion. As soon as I put a new genuine LR stat in my problems started

Right, I've done it. Ordered a Turner engine from a LR specialist in Suffolk. If that doesn't fix it there will be a Range Rover shaped Guy on the bonfire this November 5th.

andymalham said:

Right, I've done it. Ordered a Turner engine from a LR specialist in Suffolk. If that doesn't fix it there will be a Range Rover shaped Guy on the bonfire this November 5th.

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A bit rash, but in my experience you've done the right thing (no point in throwing money on a standard rover V8 beyond a 3.5). Not heard a bad word against turners. A good price for a turner built short engine and to buy a new engine from turners usually involves renewing your entire cooling system to get the warranty.

Turns out my decision was a bit rash. Latest part of the saga. So I got the new Turner motor in. Fairly straightforward job but getting the Torque convertor on was a 4 hour struggle. Fired her up and I got the same problem. After a few minutes the temp gauge went into the red and the coolant boiled up. Got my local BMW guy over and he did the sniffer test on the coolant and this showed no problem with combustion gases in the coolant. He suggested fitting some bleed valves onto the hoses so that I could be sure that I got all the air out. Reluctantly I took the hoses off and fitted two motorcycle tyre valves. One to the top radiator hose and the other to the top cabin heater hose. After 45 minutes of bleeding we finally got a good flow out of each valve. The car was a lot better. It took a long time to overheat but eventually the old problem came back. I noticed that the LPG Reducer/Vaporiser hoses were red hot on one and cold on the other. The cabin heat was almost non-existent. Decided to bypass the LPG completely and have the hoses running straight to the cabin heater which is how it would have left the factory. Guess what? It fixed it. Just done a 240 mile round trip to Staffordshire with no problem. We took the Reducer / Vaporiser to bits and it is full of pink salt! Absolutely clogged up with the stuff. I have ordered a rebuild kit and this might fix it. If not I will get a new unit.
So I now have a perfectly good engine for sale.

hi andy .well done great result ,,,, I had same problem 18 months ago ,,I have exact same car, same year with lpg zavoli multipoint.... sent engine off to wards of rugby ,complete rebuild with top hat liners ,, no problems but not cheap !!!!!! but that's the joy of owning a p38 ????? ,,now all good ,, just wondering about what you said about cleaning reducer / vapouriser on lpg system ,,,, although I have the lpg system serviced every year as of the engine serviced separately . would the service of the lpg include the cleaning and checking of said reducer/ vapouriser ????? if not where is this so I can clean it myself ,,,,as I never actually got to bottom of my problem as to why my engine went in first place !!!!!!!! all know was that one of the liners no 6 I think had gone due to overheat ,,, would welcome your answer re reducer/ vapourisor or a photo would be great if possible ,,,,kind regards and best of luck with the future ,,,Mozz

biketeacherdave said:

the fact that the bottom hose is cold when it overheats indicates either a faulty stat or the stat is air locked seeing as the car was ok before you swopped out the coolant id say the stats air locked.
i chased air locks and leaks for months mine was in the end hg failure but refilling the coolant seems to be an art form in its own.
you can drill a 4 mm hole in the outer part of the stat to aid bleeding and filling

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jamesmartin said:

a persistent air lock is usually pressurisation

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Glad you got it sorted tho people are to quick to condemned the block when often its not

Note to ourselves for the future.
"Disconnect any LPG system before attempting any overheating diagnosis."
I've heard also of gaskets in vapourisers splitting and so the LPG enters the cooling system pressuring it and adding gas which can lead to airlocks.
There's a chance that LPG in the coolant might also trigger the sniffer tests for HG failure perhaps?

^^^^^ +1 tbh its first port of call & common sense to bypass the water side of the lpg reducer & disable lpg (usually just as simple as a fuse near the + pole of the battery) when diagnosing overheating issues

mozz smith said:

hi andy .well done great result ,,,, I had same problem 18 months ago ,,I have exact same car, same year with lpg zavoli multipoint.... sent engine off to wards of rugby ,complete rebuild with top hat liners ,, no problems but not cheap !!!!!! but that's the joy of owning a p38 ????? ,,now all good ,, just wondering about what you said about cleaning reducer / vapouriser on lpg system ,,,, although I have the lpg system serviced every year as of the engine serviced separately . would the service of the lpg include the cleaning and checking of said reducer/ vapouriser ????? if not where is this so I can clean it myself ,,,,as I never actually got to bottom of my problem as to why my engine went in first place !!!!!!!! all know was that one of the liners no 6 I think had gone due to overheat ,,, would welcome your answer re reducer/ vapourisor or a photo would be great if possible ,,,,kind regards and best of luck with the future ,,,Mozz

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Well, I couldn't get hold of a Rebuild kit for the Reducer/Vaporiser so we just made a new gasket (old one had extra holes stabbed into it), out of a motorcycle inner tube. Cleaned everything up and put it back together. The system took about an hour to bleed but eventually the LPG switched over and the cabin heat came back. Took it for a good blast and the temp needle was nailed at the 12 o'clock position, plenty of cabin heat, gas was on and stayed on and no bubbling in the evap tank which kept its level. Radiator was nice and toasty hot. No whiff of gas when it switched over.
So, to break it down, I think I had an existing problem with the Reducer/Vaporiser which I didn't know about cos it appeared to work OK. I did a service on the car including changing the coolant and I didn't bleed it properly. Although these motors do suffer from slipped/cracked/corroded liners mine is actually OK.
Ref getting the LPG serviced. I don't know what is involved in an LPG Service but I very much doubt that the techie will remove and strip down the reducer/vaporiser if it appears to be working OK. If you were thinking of taking the car to an LPG man to have the system serviced I would strongly recommend that you insist that they do this. Like I said, mine had about half a kilo of pink crud in it and still appeared to be working OK.

MrGorsky said:

Note to ourselves for the future.
"Disconnect any LPG system before attempting any overheating diagnosis."
I've heard also of gaskets in vapourisers splitting and so the LPG enters the cooling system pressuring it and adding gas which can lead to airlocks.
there might be a chance that LPG in the coolant might also trigger the sniffer tests for HG failure perhaps?

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I did consider that the gas might be getting into the coolant somehow so I disabled it (disconnected the solenoid) early on in the process. I think the pink sludge was intermittently blocking the coolant flow as the feed pipes were hot and then cold and the gas was on and then off. Cleaning out the reducer/vaporiser has certainly fixed the fault combined with proper bleeding of the coolant system. I couldn't say what proportion each issue made to the fault but I'm certain that both issues played a part and both needed to be resolved to get the car working OK. Just need to turn my attention to the auto box now as it doesn't feel quite right.

hi andy ,,, thanks very much for your reply ...will get a diagram of the vapouriser/reducer and will get grandson to strip it down and clean out ,,.. I know what you mean about bleeding , its a nightmare if you don't do it right ,, its just patience and bit by bit , we changed the rad over once but fortunately having read about it before it as I said took a long time but got there in the end ,,,ok andy best of luck for future and enjoy your rangie ,kind regards mozz

mozz smith said:

hi andy ,,, thanks very much for your reply ...will get a diagram of the vapouriser/reducer and will get grandson to strip it down and clean out ,,.. I know what you mean about bleeding , its a nightmare if you don't do it right ,, its just patience and bit by bit , we changed the rad over once but fortunately having read about it before it as I said took a long time but got there in the end ,,,ok andy best of luck for future and enjoy your rangie ,kind regards mozz

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Best of luck with that Mozz. Auto box seems fine now. Had to put nearly two litres in yesterday. I think the box should be viewed as a Sponge rather than a vessel. I am going to go through the process again next week and see if I can squeeze a few more drops into it. Strange thing was that I knew that a large amount of oil had poured out during the engine change but the level test said I didn't need to add any oil. I had followed the instructions i.e. drive it around to get it warm but not hot, check the level with the motor running, go through the gears, check it again, add oil until you get a small stream. Didn't need any extra oil. Did the same thing yesterday after doing 250 miles over the weekend and I needed to add nearly two litres. No leaks visible so I can only assume that the transmission is a sponge!
P.S. shifts are silky smooth now.