iani Posted June 11, 2022 Report Share Posted June 11, 2022 My 2.5l GT6 was running just fine when I noticed steam coming from the exhaust and the temp had shot up, pulled over and awaited recovery. I removed the head, no obvious sign of damage to the head gasket and I'd convinced myself it was a poor quality part. I checked both faces for straightness against a steel rule, all looked well so I reassembled with a new head gasket, filled with oil & water and thought all was ready. I am awaiting a new exhaust manifold so couldn't start the car up, I decided to turn it over on the starter to distribute the oil, water vapour was visible from the no2 piston exhaust valve, on stripping the head again I discovered that the head has a crack. Lesson learnt, if I ever have another seeming HGF I will take a wire brush to all chambers and check before refitting. Please wait while image is uploading... Quote Link to post Share on other sites
astontr6 Posted June 11, 2022 Report Share Posted June 11, 2022 1 hour ago, iani said: My 2.5l GT6 was running just fine when I noticed steam coming from the exhaust and the temp had shot up, pulled over and awaited recovery. I removed the head, no obvious sign of damage to the head gasket and I'd convinced myself it was a poor quality part. I checked both faces for straightness against a steel rule, all looked well so I reassembled with a new head gasket, filled with oil & water and thought all was ready. I am awaiting a new exhaust manifold so couldn't start the car up, I decided to turn it over on the starter to distribute the oil, water vapour was visible from the no2 piston exhaust valve, on stripping the head again I discovered that the head has a crack. Lesson learnt, if I ever have another seeming HGF I will take a wire brush to all chambers and check before refitting. Please wait while image is uploading... That head may still be salvageable with an valve insert, I would take that head to a reputable engine machine shop. They will probably tell you it will be at your risk. A good M/C Shop will be able to pressure test there work for leaks. Bruce. Quote Link to post Share on other sites
Tim D. Posted June 11, 2022 Report Share Posted June 11, 2022 My friend had similar on a stag engine. He rebuilt it at great expense after a valve collet let go. Fired it up first time and water level plummeted and steam out the exhaust. Thought it was a duff hg so replaced and same again. Despondent he went on hols. Came back and took it all apart and there was a 5mm hold in the combustion chamber. The firm who machined the heads missed it. They were a good firm and aluminium welded it and it has been fine ever since. Cheers Tim Quote Link to post Share on other sites
Nigel Triumph Posted June 11, 2022 Report Share Posted June 11, 2022 Unlucky... But well spotted! Nigel Quote Link to post Share on other sites
RogerH Posted June 12, 2022 Report Share Posted June 12, 2022 23 hours ago, iani said: My 2.5l GT6 was running just fine when I noticed steam coming from the exhaust and the temp had shot up, pulled over and awaited recovery. I removed the head, no obvious sign of damage to the head gasket and I'd convinced myself it was a poor quality part. I checked both faces for straightness against a steel rule, all looked well so I reassembled with a new head gasket, filled with oil & water and thought all was ready. I am awaiting a new exhaust manifold so couldn't start the car up, I decided to turn it over on the starter to distribute the oil, water vapour was visible from the no2 piston exhaust valve, on stripping the head again I discovered that the head has a crack. Lesson learnt, if I ever have another seeming HGF I will take a wire brush to all chambers and check before refitting. Please wait while image is uploading... Hi Ian check the area carefully as that does not look like a normal crack. To me it looks like there is a void behind the 'crack' and it has broken through OMG Roger Quote Link to post Share on other sites
iani Posted June 14, 2022 Author Report Share Posted June 14, 2022 On 6/12/2022 at 5:51 PM, RogerH said: Hi Ian check the area carefully as that does not look like a normal crack. To me it looks like there is a void behind the 'crack' and it has broken through OMG Roger the head is scrap Roger, I have obtained another one. Quote Link to post Share on other sites
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