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thats just what mine did a few months ago, started pushing coolant(225k old 42t running 30psi), lucky i was lazy and just kept emptying and topping up the rad as a few months later i broke a crank.
so pulle3d the motor and the big girl got everything you just said plus balance the entire rotating assembly. first and last time it gets opened..lol
The td curse..

Ouch! Mine is 330K N/A recently turboed. Think I will rip the head off this weekend and check it out. Hopeful it is just a gasket but may as well give it a good going over while it's off! Bit annoyed that I only fitted the turbo set-up 3 weeks ago and now have to pull it all off again... :(:(:(
 

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nissan 4.2td patrol
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to machine the head means you have to remove precomps from head. not hard to do but most better to replace them once removed. They require protrusion when installed.
just something to consider.
But i would be sending the head for a skim and pressure test regardless of whats involved. just make sure that if your machinist machines the precomps flat with the rest of the head. clock him over the head with your head.
Just want to quickly clarify, cause my brain is a little confused ......
I understand that the sleeves need to protrude ( I think it is about ) 0.07mm or something like that, or can be flat, but never below the deck of the block, but I think the precombs have to be 100% flush with the head, as the whole precom doesn't sit in the cylinder chamber but 1/2 in the chamber, 1/2 on the head. (this was my TD42 head after a little overheating issue I had, but shows the position of the precoms.

I think you meant to say that you need to Scotch Kiss the machinist if he skims the block and the sleeves flat....hahaha
 

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Just want to quickly clarify, cause my brain is a little confused ......
I understand that the sleeves need to protrude ( I think it is about ) 0.07mm or something like that, or can be flat, but never below the deck of the block, but I think the precombs have to be 100% flush with the head, as the whole precom doesn't sit in the cylinder chamber but 1/2 in the chamber, 1/2 on the head. (this was my TD42 head after a little overheating issue I had, but shows the position of the precoms.

I think you meant to say that you need to Scotch Kiss the machinist if he skims the block and the sleeves flat....hahaha
The book says liners can be .020 - .090 proud of the deck surface but I'd suggest you don't go less than .050 above the deck. I've only seen a few TD42 heads machined and they all were machined with the precom chambers in place.
 

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nissan 4.2td patrol
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Ok... If I'm wrong, my apologies.

I could have sworn they should be flat. So how much must they protrude, or be below deck?

The head I got from Nissan many years back looked to replace the on in the pic earlier was definitively flat, when I had a straight edge across it. I never thought to check with a micrometer though. This is interesting.....
 

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Discussion Starter #27
Well it went into the mechanic's today and he said I'm stressing over nothing. He reckons just leave it for now and keep an eye on it.
 

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The book says liners can be .020 - .090 proud of the deck surface

Im not sure why they need to protrude but this is what the manual states. and given that most people who open up td42s never have a reliable engine afterwards. Id be sticking to what mr nissan says pretty closely.
 

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Yeah You are spot on with the liners having to be between .020 - .090 proud of the deck surface of the block. This helps give a better seal and squeeze on the gasket between the head and block, but the precom chambers (you mentioned "just make sure that if your machinist machines the precomps flat with the rest of the head. clock him over the head with your head), must be flush with the rest of the head. If the precoms are not flush there will be a weak point on the head gasket and the seal will not be even all around the metal ring on the head gasket.
 

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Discussion Starter #31
Just a little update I've done around 500ks since I noticed the leak and topped up the overflow bottle. The level doesn't seem to have dropped any but I still see a small droplet of coolant on the bottom of the bell housing. The Nissan mechanic I took it to said he doesn't think we should take the head off just yet he said it won't just blow out and leave me stranded I just hate knowing there is a leak. Will it cause any corrosion damage to head or block if just left alone? He said I shouldn't have to touch it until 500,000ks it only has 285 on it now. Just asking for some advice from all the nolagble people on here. After reading all the stories of machining it this way and that way. I just don't know if it's best left alone or not???
Thanks. Stressed td42t owner
 

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nissan
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There is the right way and then there is the redneck get you out of trouble way!

Mine was pushing some oil out between the head and block so I pulled the head, checked all surfaces with a straight edge and inspected for cracks as best I could with a bright light - again its not technically correct in that I didn't get it machined but did clean it thoroughly and check protrusions etc with a dial gauge, put a new head gasket on with new head bolts along with any gaskets that needed to be done since the inlet/exhaust/thermostat housings were off and put it back together again.

Did this job nearly 2 years ago and it runs like a champ. Not everyone is going to be this 'lucky' but I have confidence she is good to go anywhere at a moments notice with no fluids leaking out of it.

I wouldn't be able to drive it around knowing it was leaking something!
 

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GUII ZD30DI Wgn
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Don't know about that one, but this stuff was recommended to me by a mate who works for a car dealer, He gave me a couple, I've never used them myself but have given some to people who have had issues and it solved them. I'm told engine re-conditioners use it, I carry it as a just in case for trips.

https://gngtraders.co.nz/products/sealwel-cube-cooling-system-sealer-and-conditioner
 

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Discussion Starter #36
Just went to Dewer's performance engines and he sold me some of that block stop leak stuff. Just put it in, will keep my eye on it and see if it fixes it. He was pretty confident that it will work.
 

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Discussion Starter #37
Well the little magic block of stop leak stuff seems to have done the trick. No more leaks.
The bloke at Dewar's said it could of started leaking because of the recent coolant change with the mix maybe a little bit to strong. I just used Nulon premixed.
 

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Discussion Starter #38
Well it's leaking again. Might be time to pull the head off. Could that be a cause of my running hot issues?
 

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Yeah definitely rip head off and do it properly have the head crack tested to be sure, new head gasket and head bolts and you’ll be good to go.
 

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Discussion Starter #40
Was thinking about getting JP Performance in wodonga to do it for me. Does anyone know what his head work is like?
 
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