head coming off again

[Andre Steyn]

After a nice almost 2500km basically non stop trip, from cold to humid and extremely hot, I noticed a lot of air in the cooling system. After bleeding it out and driving again for a few km's I still get air in the system. So filled up the radiator again at watched it while idling, I noticed varying bubbles from big now and then to coke like tiny bubbles constantly, is this a head again or just the gasket gone bad?

[ricster]

Hmmmm..... difficult to say. When you bled the system was the heater on hot? If not, put the Patrol on ramps in front or get the nose up a bit, and run the engine till hot with the radiator cap off. Vary the revs to push any air out of the system. I recall on mine it took a few weeks to get the air out the system totally. Take it for a test at a radiator place to see if there is exhaust gasses in the water. This will give you the best indication.

Before stripping the motor, I would re-torque the head again. I don't know if you have done the second re-torquing of the head or not, but everything has now probably settled into place and making sure the head IS 100% torqued to the block is essential !!! Remember 22.7:1 compression ratio is MASSIVE and a leak can easily sneak past. If this doesn't solve the problem, then the problem is a little more involved.

There are a few things that could have gone wrong mechanically. Firstly, the head gasket. What make was it? Secondly the sleeves in the block. Were they a fraction proud of the top of the block ( I think 0.07mm ), or flush with the block or were they a fraction below the top of the block. Under 22.7:1 compression, air can squeeze past the head gasket and push through into the water ports. This would need you to remove the head and measure the sleeve height. If the sleeves are the problem (be aware that maybe one side of the sleeve is flush and the other side might be a fraction below the block), then there are 2 options available to you.

First and most difficult would be to strip everything again and send the block in to get them to adjust and pin the sleeves correctly. This is a VERY difficult task, and may land up that they skim the block which has other repercussions like piston protrusion. So this is possibly not the way to go.

Second option, you could piano wire the block. I used stainless steel shim stock on mine to ensure sleeve protrusion, that I cut out into rings exactly to the size of the sleeve to build it up to either flush or anything up to 0.07mm ( double check my measurement as I may be wrong on this IMPORTANT measurement )higher than the block. Use a NEW head gasket ( Nissan part ), and torque the head properly. Run the motor for a while ( +/- 500Km ) and re-torque the head again. I couldn't believe how much power I needed to finish torquing the head !!!

Keep us posted !!

[Andre Steyn]

It was a payen head gasket, never had issues with their gaskets in the past. But the retorque wasn't done yet so that has made me think will check that first. Must admit I'm worried about the sleeve protrusion, for that was done by the enginering. What should the torque on the head bolts be?

[ricster]

Head bolt torque???...... @%$&*$#@ tight ..... haha. I cant recall off hand, but there were 2 different ways mentioned. The Max Ellery book, if I recall correctly, mentions 2 or 3 torque settings to get the head to the correct torque, then you mark the bolts with a line, then you turn that head bolt ( I think ) 110 deg, but it may be 90 deg. to do this you need a looooong bar to get enough leverage to crank that bolt the full 110 or 90 deg. Use 2 people one to hold and ensure the socket stays firmly on the head bolt and the other to crank that lever !! This was the method I used.

The other way that I think is in the Nissan manual is a series or torque settings to get to the final torque. I'll have a look tonight in my Max Ellery book for the settings if you like, or maybe someone has them handy to post here.

[ricster]

Taken off the Aussie Patrol Forum... so please double check.....

Get new bolts or you won't get any warrantee on your gasket. Head bolts are done up in three stages. 1st 49-59 NM, 2nd 98-109 NM then 90 degrees.

http://www.patrol4x4.com/forum/engine-d ... lts-78150/

Did you replace the head bolts? This could also be a problem area ( they may have stretched ). If you replace them then torque and re-torque after a few Kms. If they are new bolts, then just re-torque

[tour de frans]

Remember- you can not re-torque if the finel pull was on degrees! I suppose you could but then someting else is wrong.

[ricster]

hey hey howzit Mr Frans !!!!

Frans.... Can one loosen the bolts and then re-torque them as above?

[Andre Steyn]

Hmmmm, that sounds like bad news. So the head has to come off again. Ai! Oh well the exhaust manifold gasket is leaking somewhere as well so 2 flies with one klap. Plus with the head off I'll also be able to check how the bore looks seeing that I had seating issues before the long trip, at least the hard starting is sorted now. Cranks about 3 times with glowplugs disconnected when cold so at least thats fixed.

[ricster]

May not be a bad thing really. You can look at the head to ensure there is no cracking..... excluding the small hairline cracks that are normal on precom chambers. You can even for piece of mind send the head in for pressure test. That can be a nice thing to have in the back of your mind when the motor is all back together.

[tour de frans]

Hello
A stretch bold can only be used once. I know they will give a 2nd life , but not on the patrol.
With bubbles in the cooling system, 9 out of 10 the head will come off. Bad news, but for the best.
Good luck