Hi all,

I need some help and advice. I have a 2-06 4.2 SC which is overheating after a few miles of driving. On idle it’s ok for 20 odd minutes then coolant out of the expansion tank.

Following have been done

Pressure test all good, holding pressure fine. Done by AA and local specialist garage,
New Rad, thermostat, expansion tank cap and water pump.

Still overheats. No water leaks just overheats. Heating is blowing cold too.

Any ideas please what it could be?

Thanks

Ifty

Sounds like an airlock, have a google for your specific model, probably need the front of the fatty as high as possible to bleed.. Pete
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They are a for air locking! Persevere sir…

I agree, also don't forget to bleed the electric pump as well.

Keep opening the bleed screw on the expansion tank many many more times than you would think

It took me a whole afternoon last time I did it!


David Range Rover 4.2 Supercharged 2006
Ford Focus EcoBoost 1.5 2017
MG TF 2003

Previous Cars of note
Land Rover Discovery 2
Jaguar Mk2 3.8 - Company car
MG Midget 1974 - Concours

I just replaced the hose clips on mine as they were letting by once up to pressure so after this it took an age to bleed it did it ran it for a day or so did it again same procedure 4 times each time running it for at least 40 mins cycling through all the heater controls also when I was in there changed the fan with the thermo coupler mine was weak and also had a cracked vane so it was a good end result.
Just for info mine was holding up under a pressure test but wasn't holding the correct pressure when hot. The clips on the hoses get weak so replaced mine with jubilee clips
Worth a look

I would suspect the auxiliary coolant pump iv got a 4.2 sport known issue was they were wired the wrong way round from factory and fail.
Or its wired correctly and just failed with the ignition on engine off you should both be able to hear the pump going happily on its own and feel it if you put your hand on it.

With cold heating check the heating auxiliary valve and poss air lock at the matrix you can fill the heating matrix up easily if you pull a hose off the heating valve.

https://www.ebay.co.uk/itm/235842963166?mk...media=COPY

Mine was the same so I bought a vacuum pump kit and it was great. First time no issues.

In the absence of a vacuum pump you can open the expansion tank cap then compress the top radiator hose over as much area as possible like between four fingers and palm of hand then close the tank cap while compressing the hose . That creates some draw on the coolant and the air has more chance to release . Works for me .
It can take some time for the air to release . Maybe leave the hose compressed overnight .

Gsxr1250dave wrote:

I would suspect the auxiliary coolant pump iv got a 4.2 sport known issue was they were wired the wrong way round from factory and fail.
Or its wired correctly and just failed with the ignition on engine off you should both be able to hear the pump going happily on its own and feel it if you put your hand on it.

With cold heating check the heating auxiliary valve and poss air lock at the matrix you can fill the heating matrix up easily if you pull a hose off the heating valve.

https://www.ebay.co.uk/itm/235842963166?mk...media=COPY

Radiator sealer is most likely causing a blockage somewhere . I had a brand new Freelander V6 with the heater matrix leaking after a few thousand miles and only a few months old and the dealer decided to “ fix “ it using a radiator sealant which very quickly destroyed the engine .
Going to be fun trying to clean out that V8 engine

Has it been tested for carbon monoxide in the coolant in case of cylinder head gasket failure .

Yes it has been tested for exhaust gases.

I have a friend whose brother is an AA patrolman and he said it’s possible it’s more blockage then head gasket. He said put an engine flush through it. As soon as temp is normal wait a few minutes and switch engine off. Wait say 10 mins and restart car to bring it up to temp again and let it run. If it starts to overheat then stop engine and remove coolant and see if it has any it’s of the rad sealer. If it does then keep running with engine flush.
He said you have to make sure all hoses are clear of blockages too, make sure water pump and auxiliary pump are working and remove thermostats to allow flow.

That’s good to have some professional help from the AA tech . A lot of flushing is key . There could be some tricky bits like the heater valves which might need dismantling , could maybe find a rebuild kit if you want .
The heater matrix can be difficult to clear .
It’s possible to rig up a pond pump drawing and feeding back the flushing mixture from a large bucket to flush in the opposite direction from the normal flow through the matrix hoses where they go through the bulk head .
The same flushing is possible for the engine and radiator with the thermostat removed .

Time makes a difference . The longer you leave the pump flushing the cleaning agent the better . Could take days . Much more flushing with clean water to remove all the flushing chemical . Many buckets and containers required . Think how long it takes to soak a baking tray or roasting tin and that’s an easy job compared with the time it could take to flush an engine .
Good luck

A good filter required for the pond pump suction pipe

Andra wrote:

That’s good to have some professional help from the AA tech . A lot of flushing is key . There could be some tricky bits like the heater valves which might need dismantling , could maybe find a rebuild kit if you want .
The heater matrix can be difficult to clear .
It’s possible to rig up a pond pump drawing and feeding back the flushing mixture from a large bucket to flush in the opposite direction from the normal flow through the matrix hoses where they go through the bulk head .
The same flushing is possible for the engine and radiator with the thermostat removed .

Time makes a difference . The longer you leave the pump flushing the cleaning agent the better . Could take days . Much more flushing with clean water to remove all the flushing chemical . Many buckets and containers required . Think how long it takes to soak a baking tray or roasting tin and that’s an easy job compared with the time it could take to flush an engine .
Good luck