Thread: 300 Tdi head gasket replacement - some tips

Hi,
I have just had to replace the head and head gasket on my 98 diesel Disco and here are some things that you might not know about.
1) Diagnosis - an RAA guy told me something that he had only just learnt after 30 years in the job. To check if it is a head gasket, warm up the engine, then take the coolant cap off (obviously carefully) fill the coolant up to the point where you can see the top of it, then turn the motor over with the starter only (so take the wire off the injector pump - or for a petrol, take the coil lead off) and watch the level of the coolant. If the coolant level rises, then it is blowing past the gasket and needs a new one. In my case, it spat out all over the place, even though it was only the starter motor doing it.
2) Head bolts - There are three different sorts and about 18 bolts all up. It is impossible to put the wrong ones in the wrong holes, but if you are buying a new set, then make sure you get the lot.
3) Dismantling - When you lift off the head, if you leave the exhaust manifold on, then make sure you disconnect both oil hoses at the turbo, otherwise you will stretch them and ruin them as you try to hoist the head off. Also, the two rear most head bolts can't come all the way out, so you have to hold them up as you take the head off.
4) Check for softness - I didn't know heads could go soft, but these can if they are overheated and mine was. Time for a new head.
5) Reassembly - Put the thermostat housing on first (and yes, replace the gasket for it, as these can cause coolant loss if not done), as one of the bottom bolts for this is impossible to get back in. I eventually managed it by grinding it shorter and then filing a little bit off the alloy thing in front of it. Obviously put the two rear most head bolts in too and hold these off the block using locking pliers or some other clever arrangement.

It is all back together now and runs fine, but of course it was a pain and cost me about $1500-1600 for parts and about 10 hours work, not counting the swear words.

I hope this helps the next person doing it.

Erik

Hi all,
Well having not long ago done the HG on my 300Tdi, I can tell you if you think ot is gone.....it is. Ususally no question. Yes the heads go soft if they are too hot at all. Get them checked.. mIne was fine to go back on.
New head bolts ONLY. New P gasket ONLY. Exhaust manifiold off before removing head is best.
No need for a Co2. Reasonable pressure in the morning with engine cold will tell you it's knackered.

My 10c. Oh, mine cost NZ$1700 all up to do including head machining etc.