I have done my second head gasket in 50K, as per this thread on patrol4x4
http://www.patrol4x4.com/forum/nissan-p ... lp-127777/" onclick="window.open(this.href);return false;
And I'll quote my post to make it easy
Hey guys, I am going to keep this brief if not I could write 10 thousand words on the subject.
So, black top motor on gas pre to me rebuilding it i was running up to 14psi boost, laminova cooler and 25% gas, it cracked a piston in pouring rain, blame water down the snorkel as it had been parked, or just abuse over time I dont know, but it cracked number 5, so be it, it had had the gas on for the better part of 100K and motor had by this stage done 300K.
I rebuilt it myself, but I know what i am doing, and what I didnt I had done by professionals.
the block was good, replaced liners and used GU pistons with ceramic coating, decked to the correct height. stage 3 gasket, 1.25mm from memory. The thickest anyway.
verdict from the machinist was the head was shagged, I still have it, they say it was cracked in all 6 cyls, but I think its just the pre-combs they were talking about, But I was in a rush and wanting something that would hold together so I got my hands on a genuine nissan GU turbo head.
rebuild kit and gasket and pistons supplied by SMS diesel spares, head supplied from A.C.E.R.S in Yatala, but as said, is genuine.
left for the cape with 1000km on the motor, on the way north stopped at diesel central, who had supplied the re-co 200hp pump, and set me up with United diesel in WA for the turbo.
made 190ish hp at the tyres on spanky new 35s weighing 4 tonne, so there was a bit of driveline loss, I was happy to call it 200. running 23ish max boost, EGTS well controlled, very rarely over 500
drove the cape fine, got back and after about 20K had been put on the motor every morning the low coolant alarm would be going off, lots and lots of investigating lead me to agree with every one that the head gasket was pressurising the coolant jacket
got another gasket and new bolts from SMS, had my diesel fitter mate come around and check for straight and torque it down.
initial failure was put down to incorrect HG torque, the gregorys has one NM value, and the internet has a similar torque value but then + 90* on the bolt.
retorqued it to this much higher tension with the new gasket on a clean and straight head and block, and for the past 25K it has been fine, til last week on the highway it ran warm, IE the needle went higher than usual then stayed there for a while, but not hot as such. I was towing my car trailer at the time pushing a head wind and its where I come on the high is an uphill run, then never really lays off for a few KM so I just thought it was working hard, 15PSI boost 350 ish EGT, nothing out of the ordinary for the conditions. Now looking at this, it could have been my first sign of leaking combustion pressure into the coolant jacket again. Will never know though.
now this morning flicked the ignition on, low water alarm, topped it up, went to work, had to get gear during the day, low coolant alarm, topped it up, got back, no pressure in hoses, opened it up hot and running and filled it up, drove it home tonight, rad hoses are rock hard, and got a few bubbles out of the overflow line into the overflow tank, which was full to the brim, classic sign of pumping coolant out due to combustion pressure in coolant jacket.
The ute is always let to idle down to ~160 EGT before being shut down, usually 150.
is driven hard and pulls weight and is heavy, but thats what its for?! never revved beyond where its making power, which is 3500 to 4000. gas is now at 10% and almost makes no difference whether its on or off, just cleans up any smoke a little.
So, what can people suggest may be causing this? **** gaskets? They seemed fine, but I wouldnt know...
bad luck?
something with the pump being wrong?
I am stumped, this thing was meant to hang on tight for a couple of hundred K, now its done 2 head gaskets in 50K.
All useful thoughts and opinions welcomed, happy to supply more info if needed.
Please help me out.
Cheers, Andy
I have decided to redo it with a genuine gasket and studs this time,
just wondering where people have got studs from before, their tensile rating, and what length is actually correct? Im tossing up between 130 and 140 but leaning towards 140, not sure how far out of the bottom of the hole the bolt goes, as I measure a bolt shank length at 113mm from tip to underside of head, + 20mm for washer and nut gives 133, and I guess the bolt is usually atleast 5 out the bottom, so if I bottom the studs a 140 is gonna be right?
ARP doesnt have an actual listing for them, but I reckon something must cross over, or people have done before using something?
so, if anyone has info on studs to use, or any ideas on why it keeps going to shit, I would love to hear. and yes, I will check piston liner protusion when its apart
Cheers, Andy
