Doing head gaskets on a 00 discovery,4.6.was just wanting the torque for the heads and intake,i beleive the heads are 80lbs or around that.





Thanks,tim

 

I've been reading and following all the threads I can find on this subject as I'm doing the head gaskets on my 01 D2 and here's my take on a few of theses issues.

On head bolt torque: To be honest, I think the 90/90 deg method proscribed in the manual is probably a more accurate way than using a torque wrench setting. These are machined bolts and surfaces and turning them a specific amount will put the exact same amount of stretch and tensile force on them. When using a torque wrench you are measuring the force required to turn the bolt and that can be affected by lubricity of the threads, the alignment of the bolt in the bore and lubricity of the bolt head against the landing area. Any kind of dirt or a bur of some sort can alter the torque reading, which in itself is not a direct reading of the tensile force but a rather imperfect indication using a completely different datum. The shortcomings of torque readings are well known. The head bolts for the Rover are engineered to be stretched to a specific point, they cannot be reused due to the fact that they will not achieve the same specification in a second application. I'm going to follow the manual.

On head gasket leakage: There are only two coolant ports (one at each end) where water transfers from block to head. The distance between the coolant jacket and the end of the head/block or the edge of the first or last cylinder is only 1/4 inch. If you find either middle cylinder with a steam cleaned piston it is not due to a head gasket failure. It could be a cracked head, intake manifold or block, maybe possibly even an intake gasket failure but definitely not a head gasket issue.

On pressurized cooling system and overheating: Seems to me this is probably a cracked block, behind a sleeve. Why they crack there I don't know, they shouldn't but I've seen a couple of reports and a video of a pressure test where air pumped into the block coolant jacket escapes between a bore and sleeve. My question is, if combustion gases are going between sleeve and bore and pressurizing the coolant system, why aren't they also pressurizing the crankcase? This one leaves me scratching my head.

One thing is for certain, start looking for talk about Disco head gaskets and you'll have enough material to keep you reading for weeks. If you are doing a head gasket job (like me) you can rest assured that you have plenty of company, world wide. So the question is, has it always been this way with these motors? Because the Brits have been using them in practically everything for about 50 years now and, other than increasing the displacement, they haven't made any major changes to them.

 

I bought an after market thermostat from AB. It arrived yesterday; comparing it to the one I bought from the LR dealer here in town they are dead on ***** exactly identical. They were made by the same vendor; there is no doubt whatsoever. I haven't installed it yet but I have a very bad feeling and suspect the Disco will start over heating again with the newest thermostat is in place. If it fails, I'll install bypass I rigged up, eat a big plate of crow and forget about it; at least it won't be overheating. I'll be installing it tomorrow, I'll post the outcome.

 

See "D2 inline thermostat mod ?" thread of this forum.

 

The problem persists. I am going to tear it down to the block again. I was convinced the block was okay as it had passed the pressure check all assembled. Now I feel it has to be the block and only fails after the block heats up; system pressurizes, loosing coolant very quickly but no signs of a leak, There is little if any coolant flow through the radiator; which is just plain weird. The upper loop through the block and heater core appears to be flowing well; so the pump is working. I believe the restricted flow through the radiator is caused by the back pressure created from the leak/compression of #4 cylinder. Once I verify the leak at #4 with the soapy water test(I suspect it will fail with the head removed). I will replace the block. I have read on the forum that a motor from a P38A is the best swap. I was hoping to update to a 4.6 but I don't recall if any of the P38A were 4.6. I like what I have read about Turner Engineerings motors but that is getting into some serious $$$. I did get a quote of $2K on a used 4.0 with 43K miles and $2.5K for a 4.6 with 58K miles. I'd love to go with the Turner option but that's more $$$ than the thing is worth. I like the idea of leaving the radiator I/S and protecting with a sheet of ply wood; definitely going to give that a try. I will most likely start the tear down on Tuesday. The guys at the machine shop are going to lend me some of their port seals so I can perform the soap/pressure test with the block still in the truck. If it doesn't verify I'll have to give up and sell it for parts; this is my final attempt to fix the darn thing.