Land Rover Defender

Help required: Overheating Defender TD5

Had an email this week from James, who is having problems with his Land Rover Defender TD5 overheating. Here’s the email:

I have a TD5 which recently I noticed that the internal heating had stop as no hot air would come out. Then when driving on the M25 it decided to overheat and there was a lack of power. Pulled over and most of the coolant had gone so refilled 10Litres and carried on (and had heat in the cabin again).

Drove around for a day, then on the way back the same happened again.
Took it in garage and they said heat gasket had gone, so had the head skimmed, replaced the gasket, also replace the radiator, thermostat, water pump, replaced oil and filters and had a pressure test with no exhaust gases and bloke tested with no issues found.

No I’ve taken it back from the garage as cost was going high and you can drive it normal but as soon as you give it some acceleration it blows out the top of the expansion tank.

I’m after some suggestions of what else to check?
Do you think it could be a blockage in the heater matrix?
Oh, no pipes are leaking..

Can any of you readers help out James with some suggestions as to what might be causing the problem?

My initial thoughts were cracked head, but some of you serious mechanics out there might be able to shed some more light on the situation.

Leave your comments below, or you can email me, and I will pass them on to James.


  1. First question i will ask: does the coolant get pushed out of the expansion tank when the engine is at running temperature or almost straight away when cold now the gasket has been replaced?

    Second question: was the head stripped and pressure tested when the head was skimmed because that is one way to find out if the cylinder head is cracked or not. I would naturally do this with a vehicle if it had been overheated.

    Generally if the vehicle throws out all of its coolant then there is a big issue there especially if the vehicle was still driven whilst there was no coolant in the system. The heat would have increased and possibly caused some damage. The lack of power would also indicate that the pistons would have expanded larger than usual. Was there scuffing in the bores from overheating when they took the head off?

    . Amazing that 10 ltrs of coolant can be forced out quickly.

    I would have suspected a cracked cylinder head immediately and would have advised a pressure test on the heat even if the head gasket was blown. Generally as the engine warms up any crack will open out and sometimes when a gas detector test might not show up any gas because the engine takes ages to warm up if tested with the vehicle static. Hope this helps.

    When accelerating to force the fluid out is that when the vehicle is static and engine hot?

    We see occasional problems with truck engines where the cooling system gets pressurized but no exhaust gas is present. The air compressor head gasket can fail pushing compressed air into the cooling system pushing the fluid out. Not that it happens on the Land Rover engine however.. but the pistons act like an air compressor if there is a crack or the head gasket has failed.

    Was the top deck of the block checked for distortion?

    trailerfitter :)

  2. Hi

    Sorry for delay in responding as I have been overseas for a while. Now back I need to address this again. In answer to the questions above;

    1. The coolant is pushed out almost straight away (within 2 miles or driving)
    2. The head was pressure tested and skimmed but I have recently been advised that a common fault is around Cylinder 1 on the inlet manifold side and this isn’t necessarily tested when doing a standard pressure test. I don’t know if that is true or not unfortunately.

    do the blocks normally crack as I have had 2 garages to do a compression test and both put some device in the top of the expansion tank which had some kind of liquid in it, then ran tests which showed no change in the colour of the liquid initially, then after 3-4 tests it fails the test.

    any suggestions much appreciated

  3. Have you found the cause of this please as my td5 discovery is doing the same thing. It’s fine if you drive carefully but blows the coolant out if you give her some “beans” any hard driving dumps the coolant. I’m currently driving carefully with a bottle on the overflow tube to catch the coolant .
    Hopefully you have cured yours now. If not I wish you well with her.
    Kind Regards

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