4.2 GQ cylinder heads

Submitted: Monday, Jun 16, 2003 at 21:26
ThreadID: 5488 Views:3370 Replies:3 FollowUps:3
This Thread has been Archived
People,
In these threads I read consistently about the rugged reliability of the trusty Nissan 4.2 diesel motor, I have one myself and I'm of that opinion as well, however, I recently installed a 4.2 turbo engine which I rebuilt from a tired out normally aspirated engine I snaffled from an engine wrecker, the engine had done moderate k's around the 200 thou I was told, with the internal wear this seemed to fit, when it came to the cylinder head it was cracked in two places, the biggest crack being in the number 4 cylinder, I then searched high and low to find another cylinder head, a good crack free head was impossible to find, rare as rocking horse droppings after a couple of months I found one with a certificate from an NDT mob telling me it was crack free, I must of looked at 15 cylinder heads to get this one, I only had two crack tested, the first one failed.
A work collegue has just gone through the same exercise, whilst away his engine started using water there was no external evidence, only a little bit at first but as he crossed the bridge in Perth on his was back home the engine expired, his GQ got him home and didn't die in the scrub, see they are reliable and bomb proof. This head was cracked through the no 4 cylinder and also number 2.
Tonight I've just taken the old cylinder head off my original engine which had done around the 195 thou and wasn't using water, again the head is cracked through the number 4 cylinder exhaust to pre comp chamber, there is evidence of a slight moisture around the crack, but this head is U/S. I was planning to do the engine up and sell it, well that plans gone out with the tide right alongside the cylinder head.
A new cylinder head is around the $1400 mark with out anything like valves and springs and other important bits, it cost my collegue over $3000 to get the head replaced by the garage, he took the easy option.
This is an information thread more than anything else, only based on my experience others may have better experiences, just be aware.
I'm not rushing out to buy a Landcruiser, sorry, all makes and models have their shortfalls, this is one I wasn't aware of when I was changing the engines over in my GQ, I had to jump over a pile of Landcruiser camshafts to get to my recon head, but that must be another thread.................
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Reply By: Truckster (Vic) - Monday, Jun 16, 2003 at 22:13

Monday, Jun 16, 2003 at 22:13
Good Post.

Mate bought a Petty GQ round 2 mths ago, then the head went, but GQs on LPG have a habit of this... Same thing with the head, lookin for one, but his rebuild is $1000. Its ready to pick up, but hes waiting to get the $$ ...

Wanna sell ya old tired motor? :)
AnswerID: 22721

Follow Up By: Martyn (WA) - Tuesday, Jun 17, 2003 at 11:02

Tuesday, Jun 17, 2003 at 11:02
Truckster,
If you want to buy it it's up to you, I was just going to build it up as a bit of a project, it's my hobby. I have another motor I'm now starting on for my Rangie so if you wish to inject some cash into that project by buying my old 4.2 be my guest, if you want to give me your email address I can send you a list plus photos of what you can have and we can agree a price, can I assume by your login that you have a trucking business? Otherwise the cost of getting the engine to you could be prohibitive, your call, the answer is yes I'm willing to sell the old motor, plus manifolds injectors, injector pump, and other bits, send me your email. Keep the shiny side up
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FollowupID: 15012

Follow Up By: Truckster (Vic) - Tuesday, Jun 17, 2003 at 11:11

Tuesday, Jun 17, 2003 at 11:11
Mail me offline.
vfr750fv
at
yahoo
dot
com

Na not in a truckin busso just like Chevie Chase, his Family Truckster type holiday to Wally World seems to be what happens to us everytime we leave home!! GQ is solid as a truck, and carrys my family!

Also just after a project and to learn about diesels internally. Never had one apart. Had plenty of bikes in bits over 20yrs!
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FollowupID: 15013

Reply By: Member - Simon- Tuesday, Jun 17, 2003 at 07:18

Tuesday, Jun 17, 2003 at 07:18
I have heard that Nissan 4.2 diesel engines often cannot be reconditioned, especially when they have been overheated. It is common for the the cylinder blocks to crack because the cylinder walls are thin, and you dont find out about it until you press the old liners out. A friend of mine in the secondhand engine parts business told me that he once had to go through about 10 cylinder blocks pressing the liners out until he found one where the cylinder walls were not cracked. I would be wary of reconditioning one where the head was cracked because it would be sure to have been overheated.

Simon
AnswerID: 22744

Follow Up By: Martyn (WA) - Tuesday, Jun 17, 2003 at 08:52

Tuesday, Jun 17, 2003 at 08:52
Simon,
Not to sure about the "sure to have been overheated bit", my understanding was it was the actual head design and where the head has dead areas in the cooling water jacket, so it's more of localised internal overheating of the cylinder head rather than the whole engine being run at elavated temps. If it was one or two heads that had cracked I could accept that, but I can't believe that all the engines that were taken apart trying to find one uncracked head had all been knowingly overheated, sometimes we have to accept that yes this is a bad design and you, we and I have to live with it, if you have a 4.2 GQ that is. My work collegue has had the new head drilled and by-passes fitted with a vent so the dead areas can be vented, this to me seemed to be a tad OTT, everything is down to choice. I can't see myself going to this much trouble. I have a thermo couple fitted in the turbo outlet, I keep an eye on this so I'm aware of the exhaust gas temp, with a good radiator fitted it's amazing how hot the exhaust can get without having a big impact on the temp gauge in the dash I now understand why the radiator overflow bottles crack..... Keep the shiny side up
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FollowupID: 15008

Reply By: desert - Tuesday, Jun 17, 2003 at 09:48

Tuesday, Jun 17, 2003 at 09:48
Spot on Martyn. One thing the TD42 will not tolerate is overheating. Cook it once and you're done. Likewise, the pre-chamber diesels will not tolerate high cylinder temps from "boosted turbo's", and suffer cracking as a consequence. Over fueling is the main cause of cylinder head overheat. Owners trying to get that little bit more out of the old design, pay the price in the end.
AnswerID: 22756

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