Bent valve diagnosis

[EsSeX dAn]

Apart from removing the head is there any way to diagnose a bent valve? im thinking compression test. would i be able to remove the cam and tapetts and see it? would it have smashed the pistons up if theres been contact?

[Bandit127]

What engine type? Mostly, if the cam belt has gone you will have bent valves (the Mk3 1.8 was a 'safe' engine I think - I don't know about earlier engines). My AGG is not - broken cambelt = valve piston interference on that. Even at tickover.

People that say "it went bang but I put my foot straight on the clutch and pulled over - do you think it will be OK?" don't understand how many revolutions the bottom end of engine will have done in that half a second or so.

A compression test will definitely tell you if the head needs to come off for further investigation.

Unless you have been really unlucky the V angle of the valves means the valve stem gives before the piston breaks.

On the Peugeot 1.8/1.9 diesel engine (for example) they are vertical and a piston usually gets holed due to the extra strength the valve presents. 

[Wayne]

Doi a compression test as a 1st step.

[EsSeX dAn]

sorry its a 1.9tdi non pd. it didnt snap but the tensioner fell apart a bit so the belt went a bit slack. going to re tension it and go from there. im hoping it was ok as the top and bottom tdc lined up ok but fuel pump was waaaay out. so its new engine really if pistons hit valves isnt it. my current engine has 177k anyway so not worth rebiulding in my opinion

[Bandit127]

sorry its a 1.9tdi non pd. it didnt snap but the tensioner fell apart a bit so the belt went a bit slack. going to re tension it and go from there. im hoping it was ok as the top and bottom tdc lined up ok but fuel pump was waaaay out. so its new engine really if pistons hit valves isnt it. my current engine has 177k anyway so not worth rebiulding in my opinion

Don't know about the valve angle on your engine but the compression ratio means it is not 'safe'.

It sounds like your luck is in as the cam is still timed to the crank.

If not - unless your luck is really bad you might just have a head to take off and put some new valves in. Lots of people just replace bent valves with new ones and are fine. Even if you get a friendly garage to do it, it might be cheaper than a second hand engine.

If your cam and crank stayed synchronised then thank your lucky stars and buy a lottery ticket tomorrow night...    Let us know how you get on.

[EsSeX dAn]

fingers crossed and toes and just about everythin lol as it happens i replaced the head 2 weeks ago so i have 8 valves spare. im hoping its not bust the piston

[Wayne]

Going to be lucky on a diesel to have not bent a valve or 2

[scarr89]

What engine type? Mostly, if the cam belt has gone you will have bent valves (the Mk3 1.8 was a 'safe' engine I think - I don't know about earlier engines). My AGG is not - broken cambelt = valve piston interference on that. Even at tickover.

People that say "it went bang but I put my foot straight on the clutch and pulled over - do you think it will be OK?" don't understand how many revolutions the bottom end of engine will have done in that half a second or so.

A compression test will definitely tell you if the head needs to come off for further investigation.

Unless you have been really unlucky the V angle of the valves means the valve stem gives before the piston breaks.

On the Peugeot 1.8/1.9 diesel engine (for example) they are vertical and a piston usually gets holed due to the extra strength the valve presents. 

Hmmm, where abouts in Soton are you based mate? Remind me to nip over next time I have an engine issue...You sound like R2D2 talking engine jibberish like that 

[EsSeX dAn]

Right,update time. when the tensioner was removed there were bits of it missing,which i found behind the bottom timing belt cover. i refitted the tensioner as a temporary to check all compression and timing etc. so retimed it, put the old tensioner on as a temporary and tried it.........and it fired on the key! so looks like the fuel pump timing was just out. result!

[EsSeX dAn]