88 Mav Head Problems! (4th time and counting) :(

[SWB Mavi]

Hi All,

I've been reading on this site for a while and have gleaned alot of info over that time so thankyou. But now i need some help -my dad's 88 Maverick (TB42) has done the head for the 4th time (and only 10,000 km's since the last time). We haven't got it off yet but there is water in the oil, he noticed steam out the exhaust, running rough and the overflow tank filled up -the whole catastrophe!

He's had, at various times, machined the head, reseated the valves, had a crack welded up and the coreplug holes in the head welded too.

Has anyone else had similar probs with the 4.2 lt petrol engine?

And if so is it recommended to replace the head bolts when any work is done on the head? -we've never replaced them.

We've done a compression test and they read as follows:

No. 1 160
No. 2 165
No. 3 170
No. 4 165
No. 5 155
No. 6 170 PSI

Is 15 PSI variation normal or too much?

i should also add he runs on LPG most of the time and uses Valvesaver as well. We've also only just learned about the extended rotor button solution to missing and will be fixing this ASAP.

Thanks to anyone who can assist!

[Brunsy]

Unfortunately aluminium gets harder with time, the process is called age hardening. Thermal loading also does its bit to make the material brittle. Most machine shops wont weld these heads in particular as the welding process causes problems of its own.
I have replaced the head on my TB recently and i believe its mostly to do with the LPG burning hotter and stressing an allready hi kay cylinder head. The only option i was going to take was a new head casting from nissan.
Ring Orger engines in Bayswater vic they will tell you exactly why this happens to patrols, they have done literally thousands of them all successfully.
Mine is 30,000 kms on the new head with flashlube and no probs, now time for the turbo.
I assume you are re-torqueing the head as per specs.
Cheers Brunsy

[MEX]

Check your water pump & front timing case.

I am reassembling my engine at the moment after initially having overheating problems which in turn caused head problems. I initially removed my fan belts to try and rock the pulley of my water pump to check the bearing and this appeared to be ok so I didn't bother removing the pump. Big mistake. I have since removed the water pump when the head finally blew completely and found that although the water pump was ok the timing case which provides the back wall of the water pump housing had a hole corroded through it with the x-sectional area of a 5 cent piece. This hole would prevent the pump from working at its required efficiency which would cause the engine to overheat under load.

If your timing case needs replacing it will cost you $500 from Nissan or around $125 from an engine wrecker.

Beast of luck

[bogged]

A mate went through this a few times too, he was told that repair once then toss them.

Head was $1100 from nissan and fixed his issues.

others have had them rebuilt a few times and been ok.

[damige]

if you want to keep it going get some seal-wel, my tb42 head has been done 3 times and for the last 12 months ive been putin seal wel in to rad and it keeps going i re did tappets the other day and i could see the crack in the head from the centre of rokker post through to outer edge of head on inlet side.
also a freind had a leak in his motor and his mechanic could not find it so i toll him to try it and leak has stoped. it comes in a block about 20mm sq 40mm long and u just put it in radiator.

[Daisy]

has the head been pressure tested?

has it been checked if its straight and has it previously been straightened before?

has it had a check on the hardness... if it is under an acceptable amount... it doesnt take a lot for the head to warp again.

Your best bet is to find another head and take it to a shop and have it tested for hardness if its within the acceptable limit, get it shaved and pressure tested and whack it on.

TOM

[gqtrol]

tb42s and head gaskets is a common thing as far asi have been told did mine 16thou ago still going strong they seem to have a common problem with them especially if they are on gas what i was told by numerous people is that the cooling system some how createes an air bubble in the rear of the head that in turn causes it to over heat then pop especially gas vehicles as gas burns hotter i have been told you can have the head modified what they do is put a cooling hose fitting in the back of the head to stop this air bubble happening i found this out after doing mine so not sure if true or if it works but in your case four gaskets could be worth looking into on the other hand if your problem is over heating causing gaskets to blow make sure your cooling system is bleed properly that the themostat,vicous/themofans and water pump are in working order make sure raditor isn't blocked and cooling galleries in the block haven't coroded up most important if you plan on re-fitting your current head have it X-rayed,pressure tested and make sure head isnt warped before you go and waste $1300 on a new head look into it properly as the head may not be the problem just my two cents hope it helps
GQTROL