Pressure in header tank

hi all,

Looking for some advice. My defender has a tdi lump from a disco in it with the old disco temp sender in it so gauge always sits high. What Iv noticed is the system is pressurising badly and temp gauge rising quickly.

I’ve tested for exhaust gases but don’t have any in header tank and oil filler cap seems nice and clear. What could be causing excess pressure in header tank?

Kyle

Warped cylinder head, blowing between no. 2 and 3 cylinders. Possibly caused by overheating in the past. Cure? Head off, pressure test the head, if it's ok skim and refit with the correct thickness head gasket. Pressure test and skim will be about £80. Gasket £20, only buy a genuine or oem one. Or you could try one of the bottles of miracle goo out there, k-seal, irontite or similar but I wouldn't waste my money, just do it properly once.

Thanks for the quick reply, you mention correct thickness of head gasket. I dint realise there was different thickness ones so what should I be looking for?

spurs said:

Thanks for the quick reply, you mention correct thickness of head gasket. I dint realise there was different thickness ones so what should I be looking for?

Click to expand...

There's a 'tab' on the gasket that sticks out of the side of the cylinder head. There are holes stamped through the tab and these holes tell you how thick the gasket is. You get 1 hole, 2 hole, 3 hole, 4 hole and no hole. 1 hole being thinnest and no hole thickest. If you have to have your head skimmed, you may need to get a thicker gasket.
EDIT
Should have said that the clearance between the top of the piston and valves is pretty slim. If you need to get the head skimmed you will reduce this gap. I thicker gasket compensates for the loss. It's more complicated than that, but essentially that's the gist of it.

Basically the more you skim off the head the thicker gasket you need to use. The machinist who skims your head should be able to tell you how much they took off and how much has been taken off previously by looking at the old head gasket, they have either 1,2 or 3 holes denoting thickness. Googling will tell you which is which.

Just slap a gasket on it no need for a skim, it will be fine, I have done several, the bolts will go again so minimal cost.