Presure Test My 4.0 Block

Colin from Hull · Mar 16, 2011

Hi, I bought my 4.0 Autobiography (manual) quite a while ago,it came to me with the engine partially dismantled (overheating problems). I have decided to re-assemble going through everything then see what happens. So i have made some bits at work and have pressure tested my block at 3 bar, photos added, so what do you reckon maybe not 100% with it been cold but its holding pressure, also all liners are flush and all pistons heads are the same colour (black). Cylinder heads are work,for re-skimming,grinding valves, and replacing stem seals. What I did notice is some play in water pump when checking for play using fan, could the play be in the fan? Any advice will be appreciated. Colin

Irishrover · Mar 16, 2011

3bar is a good check for the cooling side of the block but remember that the pressure generated in the cylinders is around 10 bar+. When the engine is cold, the aluminium block contracts and is less likely to show any liner related problems. As you are aware, aluminium also has a higher coefficent of expansion than your cast iron liners. The wear in the water pump could have an effect on the cooling loss/overheating due to coolant loss when the system pressurises, also, the wear could cause pressure loss which in turn would contribute to higher running temperature.
If the piston crowns all look similar, without signs of "Washing" on one or more, chances are that liner slip is not the problem.
Regarding the heads, put them on a blued up surface plate and check for flatness, if they look pretty good, don't skim them just for the sake of it.

jamesmartin · Mar 16, 2011

i used do do this regulary but we found you had to have block and water inside hot ,for crack behind liner to show with water dribbling between liner and block ,if i remember rigth it was normally drivers side,and passenger on 3.9 as early water used to push water through one side more than other,washed pistons want allways the case as pressure went from cyilinder down to crack into water jacket,they would seal unless hot ,we even removed lots of liners to prove they where cracking as lr wouldnt acknowledge at time ,the mian faul lies in the fact casting still has 3.5 ali cast bore thickness but with 200 thou removed to fit 3.9 -4.6 liner

eightinavee · Mar 16, 2011

jamesmartin said:
i used do do this regulary but we found you had to have block and water inside hot ,for crack behind liner to show with water dribbling between liner and block ,if i remember rigth it was normally drivers side,and passenger on 3.9 as early water used to push water through one side more than other,washed pistons want allways the case as pressure went from cyilinder down to crack into water jacket,they would seal unless hot ,we even removed lots of liners to prove they where cracking as lr wouldnt acknowledge at time ,the mian faul lies in the fact casting still has 3.5 ali cast bore thickness but with 200 thou removed to fit 3.9 -4.6 liner

Exactly - and thats why its a crap engine !

Presure Test My 4.0 Block

Colin from Hull

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Irishrover

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jamesmartin

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eightinavee

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