intermittent overheat and hevac

Hi all, can anyone please shed some light on this fault. About a month ago whilst driving my 2001 4.0 V8 P38, the temp gauge shot straight up to the red and red light on, i pulled over and it went straight back to normal, checked the engine not over heating. over a month or so it done this a few times, sometimes accompanied by the dreaded book symbol on the hevac. The other day it done this a few times, one time it stayed in red for a few minutes, so i pulled over, steam was coming out of the expansion bottle, water had been spat out the left side of the car and all over tyres etc. after about 2 minutes it was normal, i drve to a petrol station, topped the water up(which spat out under pressure) and drove home with no further problems for about 15 miles. any ideas please as dont want to risk another overheat

Sounds a head gasket failure to me. Do you get bubbles in the expansion tank when you rev the engine?

Sounds like head gasket posably waterpump starting to fail but since it has already overheated ill put money on your head gasket is fecked now! even if it wasent the cause of the overheat
The hevac is a differant issue it has no control of the engine cooling

odysseus said:

Sounds a head gasket failure to me. Do you get bubbles in the expansion tank when you rev the engine?

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Agrr beat me to it

Easy way of checking h/g is run it up to temp and feel the water pipes
If there solid and feel like there full of sand theres a good chance the h/gs ####ed

thanks for the replies. I have driven it around this weekend, the gauge shot up to red once, for about 2 secs and back down. The pipes dont seem hard at all when running at temp, the coolant/expansion bottle is still up to level with blue coolant and the oil is still nice and golden. just not sure why it intermittently shows an overheat for a few seconds. would that defo be the hg

considering selling it but don't want too as the missus said she doesn't want another P38 and wants a disco!

If the pipes dont over pressure you may have got away with it
Errm maby the water pump starting to slip ,thermostat jamed?

darth510 said:

thanks for the replies. I have driven it around this weekend, the gauge shot up to red once, for about 2 secs and back down. The pipes dont seem hard at all when running at temp, the coolant/expansion bottle is still up to level with blue coolant and the oil is still nice and golden. just not sure why it intermittently shows an overheat for a few seconds. would that defo be the hg

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Quite sure your coolant should be Red, it's an aluminium block.

a mate of mine suggested the water pump(that sounds fun) or thermostat. will try thermostat first or go for both? just read up on replacing the water pump so may get a mechanic pal to do it.

Druim said:

Quite sure your coolant should be Red, it's an aluminium block.

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does that make a difference?

does anyone know if either or both the water pump or thermostat would put the hevac light on?

darth510 said:

does that make a difference?

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Doesn't matter IMO as long as you don't mix them.

Datatek said:

Doesn't matter IMO as long as you don't mix them.

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Don't know what's in the blue stuff but the red one contains only Ethylene, Glycol & non-phosphate corrosion inhibitors, recommended for aluminium.

Many forget to change out the coolant, even the long-life is only recommended for about 5 years.

Druim said:

Don't know what's in the blue stuff but the red one contains only Ethylene, Glycol & non-phosphate corrosion inhibitors, recommended for aluminium.

Many forget to change out the coolant, even the long-life is only recommended for about 5 years.

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One is OAT organic and the other is not. It's all either Ethylene Glycol or Propalene Glycol over here and generally green in colour.

darth510 said:

does anyone know if either or both the water pump or thermostat would put the hevac light on?

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Neather would
The hevac has nothing to do with the cooling system other than a fan that blows over the heater matrix to give you your warm air in the car.
To the best of my understanding the only electrical part of the cooling system is the temperature gauge and thats not conected to the hevac in any way

my mate came round tonight and we started it and left running on the drive in the 26 degree heat for about 20 mins, then took it for a drive and again left it for a while running! no problems whatsoever. Only thing i could think of is that the coolant cap wasnt on secure enough for it to vent as it does require an extra turn after it appears tight? and that the coolant temp sensor is playing up now and again?? but need to regain my trust in it as dont want the other half to be miles away with the horses hooked up to it

To get that trust back it may need some further diagnosis. I had pretty much the exact same symptoms and it went into a repair shop 3 times (under warranty) before they decided it was a cracked block. Not that yours is necessarily the same, I certainly hope not mate. But doing checks for exhaust gas in the coolant, and pulling the plugs to see if one is steam cleaned would be further simple checks in addition to those already suggested.

Mine has been fine for 3 years since sorting it, but that's easy for me to say as I didn't have to pay for the replacement block!

Cracked heads, slipped liners duff viscous, water pump or stat etc often will not cause an overheat until the engine is put under load, a steep hill or pulling a trailer, leaving it idling will prove nothing unless the problem is really bad, it just burns money.

ok its been weeks now and no re-occurrence done over 200 miles and not one flicker of the gauge, spoke to a few LR enthusiasts who said mine is the 4.0 Thor engne and 'bullet proof! but i have only driven it normally! i will try putting it under load up a hill and see what that does. just dont have the trust back yet

darth510 said:

ok its been weeks now and no re-occurrence done over 200 miles and not one flicker of the gauge, spoke to a few LR enthusiasts who said mine is the 4.0 Thor engne and 'bullet proof! but i have only driven it normally! i will try putting it under load up a hill and see what that does. just dont have the trust back yet

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:hysterically_laughi:hysterically_laughiBullet proof if you don't count HGF and slipped liners