poss head crack?

[SUMNIDE82]

Hi there. part ex'd my 91 range rover v8 for a j reg 2.4td surf on friday.
thought i'd got a good deal. surf overheated on sunday nite!
heard before i bought it these trucks are prone to coolant probs/heads cracking etc. car had so called recon engine fitted a few months ago.
looks as if this is now having problems.
flushed coolant system last nite,topped up coolant, ran car with rad cap off, overflowed a bit.
put cap on, ran car for approx 30secs, coolant system immediatly pressurised.
went to ease off rad cap and blew off with massive force nearly took my mates head off! surely the coolant system should not pressurise as quick as that.
anybody now any sure way to diagnose a head crack situation without taking
the head off?
i've got a 3 month parts and labour warranty on the car, and before i did the deal i asked if this would definatly cover any head probs and the answer was yes.
only prob is i think the dealer covers this himself and i know he's likely to not want to take the head off just as a precaution. took it back last nite and by the way he was talking he's prob not going to do anything with it until he sees it overheat himself.
any suggestions appreciated!!

[NiftyNev]

Do not do anything to the vehicle yourself.The dealer may see this as a way out of warranty and suggest that you broke it.Take it back and let him see for himself even if you have to tow it there.

Neville

[Guest]

Do not do anything to the vehicle yourself.The dealer may see this as a way out of warranty and suggest that you broke it.Take it back and let him see for himself even if you have to tow it there.

Neville

Neville's right, get the dealer to do it. If the coolant system is pressurising that quick I think you can definately say that the head has gone. Bear in mind the pressure when running shoul be no more than the rad cap pressure which is 0.9 bar (or maybe 1.1 bar like mine). 0.9 bar will not blow the rad cap off with that much force.

Only real way to test without removing the head is to use a pressure tester. When my head went I used a pressure tester and the system was pressurising to over 3 bar within 10 seconds of starting the engine.

Cheers and good luck

[Koi]

12 psi won't knock your head off, so I suspect for starters the rad cap is duff as it should allow any excess pressure out.
As said let him sort it don't touch anything else or admit to having done so already. If he wants to see it overheat then let him drive it til it does, you drive it round til it overheats and he'll say it was your fault for continuing to drive it knowing there was a problem.