Blown head ??

[5inchgq]

G'day all,
I recently fitted a hitachi turbo (standard GU fitment) to my TD42 and had the pump tuned to suit and after about a 1000klms it started to pressurise the cooling system. Ok so I thought the worst and replaced the engine with a good second hand one and have no dramas since. Now I have literatly (sp?) just finished pulling the head off the TD42 that I removed from my truck and there are no blown bits of gasket or visible cracks anywhere ???????

One thing I notice when removing the head studs is that a few seemed easier to 'crack' than others, so what are the chances that the head was lifting enough to put pressure into the cooling system ??? Has anyone else come across this ???

Cheers,

Dan.

[THE-Burger-Ring]

thats a tricky one. how much boost were you running? it could be a hair line crack that opens when motor is at operating temperature or under load temperatures.. how did you notice it pressurizing? what did the temperature gauge do.

[5inchgq]

thats a tricky one. how much boost were you running? it could be a hair line crack that opens when motor is at operating temperature or under load temperatures.. how did you notice it pressurizing? what did the temperature gauge do.

I was running 11lbs as from what I understand these Hitachi units aren't good for much more than that.

I noticed it had filled the overflow bottle for tha radiator so I drained it down to the 'minimum' level and checked the water level in the rad and topped it up. And it took about 50klms of driving to fill it again.

After I turboed it I noticed the temp gauge sat at about a third which was up from where it sat when the truck was N/A,(I was told to expect this) But the hottest it got was about half way on the gauge with an EGT of 430 deg.

I spoke to a head specialist yesterday and he mentioned the whole hair line crack scenario which I had also considered, he also mentioned that he has seen cracks in the pre-combustion chamber, which is something I have never heard about a nissan.The other thing he mentioned was that the TD42 blocks can crack the parent bore.

I'm stumped because at 270 thousand k's every thing else looks great, no ridges in the bores only hone marks, the carbon on the piston crowns I can wipe off with my finger etc.

Cheers,

Dan.

[sswaffie]

Hay mate just a thought? is the radiator cap holding a pressurised system?
Might explian the over filling of the o/f bottle, and make sure the o/f bottle
little spout inside is connected correctly to the hose coming from radiator,
I have seen the little hose connected to the wrong outlet on top of the
O/f bottle so when system cools down it can't recover coolant from the bottle
Just an idea you may have already checked these things , i have seen heaps
Of radiator caps not sealing in neck of Radiator . Most prob not the running
Warmer problem but you may have more probs than one , as for precombs
cracking, yes is very common
Swaff

[5inchgq]

Hay mate just a thought? is the radiator cap holding a pressurised system?
Might explian the over filling of the o/f bottle, and make sure the o/f bottle
little spout inside is connected correctly to the hose coming from radiator,
I have seen the little hose connected to the wrong outlet on top of the
O/f bottle so when system cools down it can't recover coolant from the bottle
Just an idea you may have already checked these things , i have seen heaps
Of radiator caps not sealing in neck of Radiator . Most prob not the running
Warmer problem but you may have more probs than one , as for precombs
cracking, yes is very common
Swaff

Everything you mentioned I had done by you after I fitted the second motor even though I still havn't gotten around to dropping the radiator yet it is on the list after I get my front diff back in

What usually causes the the precombs to crack ?

Cheers,

Dan.

[sswaffie]

Could be a few things , overfueling or over a period of time from being hot
then cold so many times . They have sharp edges on them and this is where
they usally start to crack , you could put turbo precombs in wich have a larger
ports and addition of relief holes, you could then still clean any sharp edges
off around the main port to help prevent cracking. Some people dont worry
to much about the cracks and run them again but i like to give every thing
the best possible chance , on assembley.

[garth]

gudday

if you are going to go to the trouble of replacing the pre coms (i have never bothered unless they are heavily cracked) you should do the inlet seats at the same time.
The head specialist who did some work on my truck found the standard nissan inlet seats are not made from the same material as the exhaust seats and had worn considerably. Yet the exhaust were like new.

It depends on how hard you are wanting to push the engine though and how deep your pockets are.

precoms cracking can be a few things but the main one is high egts, dissimilar metals cool/heat at diffent rates hence cracking, as said radiusing removes weak spot and can help, there are very good after market ones available - I can hunt down the name of them if needed.

good luck