Head Gasket?

[Trevor450]

I have noticed an issue over the last few months with my 450. I first spotted it when the heater wasn't working as well as it should be so I bled the cooling system.

The car keeps blowing coolant out of the expansion cap lid when I come to a stop. When the car has cooled down, the expansion tank is full to the brim but the swirl pot has a good two to three inches of air in it as does the radiator. I bleed the system again and it is good to go but the problem keeps repeating.

I have ordered a new cap for the expansion tank and I have also ordered a block tester kit to test for hydrocarbons in the coolant.

The engine seems to be running OK and doesn't feel down on power and it isn't overheating either. It is using oil but I have a leaky rocker gasket and there doesn't appear to be any coolant in the oil as far as I can tell. The exhaust is quite wet especially on startup but I don't get clouds of steam as I would expect if the HG was goosed.

[ChimpOnGas]

Remove each spark plug in turn and examine.

If one or more looks super clean it's because it's been steam cleaned by the presence of coolant entering the cylinder.

Rotate the engine one revolution as you remove each plug, are there any spits of coolant coming out of the plug hole as you turn the engine over by hand.

Do a compression test on all cylinders, are the figures consistent?

If the block has gone porous coolant will act as a lubricant between the outer face of the liner and the block, the liners are just an interference fit.

The result will be a slipping liner which can give very similar symptoms to a failed head gasket, again look out for that steam cleaned spark plug.

[TJC46]

Trevor450 said:

I have noticed an issue over the last few months with my 450. I first spotted it when the heater wasn't working as well as it should be so I bled the cooling system.

The car keeps blowing coolant out of the expansion cap lid when I come to a stop. When the car has cooled down, the expansion tank is full to the brim but the swirl pot has a good two to three inches of air in it as does the radiator. I bleed the system again and it is good to go but the problem keeps repeating.

I have ordered a new cap for the expansion tank and I have also ordered a block tester kit to test for hydrocarbons in the coolant.

The engine seems to be running OK and doesn't feel down on power and it isn't overheating either. It is using oil but I have a leaky rocker gasket and there doesn't appear to be any coolant in the oil as far as I can tell. The exhaust is quite wet especially on startup but I don't get clouds of steam as I would expect if the HG was goosed.

Your on the right track with the new cap and the tester kit.

Also some excellent advice from chimpongas which is worth doing.

You say the car isnt down on power and doesnt overheat....it could be a simple air lock. The cooling system on these cars can be a baard to bleed out and remove any airlocks.

I had a similar problem and like you, the first job was to renew the expansion tank cap. My next problem was i could not undo the nut on the swirl tank to top up and bleed.

My alternative and eventually successful method was to fill the system using the hose from the top of the 2 heater pipes. If you remove the hose off the pipe and slacken the clip where it is attached to the inlet manifold, turn it thru 90 degrees, you can place a funnel in the hose and add coolant thru it.

It now is easily the highest point on the system so gravity makes it work. Undo the rad screw and fill the system till the rad is full. Now undo the expansion bottle cap and fill the system, again thru the funnel, till the level within the expansion bottle starts to rise......you may also find coolant coming out of the now open end on the heater pipe at this point....but that is also a good sign as it means the feed and return pipes,and heater are also full of coolant.

You now need to reinstate everything as it should be,and run the car up to temp, let it cool and repeat again. If it is just an airlock, the above method should clear it!

Good luck and lets hope it is something quite simple.

[blitzracing]

Most garages have a simple chemical test they run on the cooling fluid to show exhaust gas has entered the cooling system. A lot easier than running a compression test on 8 cylinders.

[Trevor450]

blitzracing said:

Most garages have a simple chemical test they run on the cooling fluid to show exhaust gas has entered the cooling system. A lot easier than running a compression test on 8 cylinders.

That's the kit I have ordered. It wasn't expensive.

[Mr Supercharged]

I had a similar problem to you, kept topping up the coolant etc, the rad water level would reduce and so would the level in the swirl tank. It wasn't a major loss, you just had to keep topping up and if the expansion tank was more than half full, which it should not be it would leak around the cap. I finally, after 10 years found out what the problem was, the brass screw on the top of the header tank had been leaking. I had already replaced this with a brass bolt off Ebay. The trouble was that the o-ring supplied with the bolt was not the correct size, and every time you undid it and did it up again the o-ring would suffer damage. So I replaced the o-ring with the correct size (20% compression) and used Loctite thread sealant on the thread. This resulted in no more water loss and no more over pressurisation. It might be worth trying this once you have bled your system again.

here are some useful links:

http://www.ebay.co.uk/itm/LAND-ROVER-DEFENDER-200-...


http://www.ebay.co.uk/itm/LOCTITE-577-THREAD-SEALA...

[Trevor450]

That's interesting. I'll take a look, thanks.

[Trevor450]

My combustion leak test kit arrived today so I gave it a go. It failed so it is pointing towards HG issues. It took a while to change colour so it isn't a massive leak at present but it is going in tomorrow.