16v bent valves but running fine?/Headgasket misfire??

18th July 2010, 21:21

my friend is going to see a 16v 106 gti
and he said to me hes apparently heard previously the car has bent a valve. about 6 months ago)

would you notice a running difference in the car if a valve was bent?
any ways to check?(without taking it apart)

18th July 2010, 21:23

It wouldnt work at all if the valve was still bend. Would need a shit load of work

18th July 2010, 21:23

Could use an endoscope to look at pistons through spark plug holes - should be able to see some damage where the valve has caught one.

I imagine the car would be a bit down on power?

18th July 2010, 21:27

mine did this, run fine for 5 month jus a little tappy then one day whilst driving hard bang n smoke it dropped a valve n cut through my piston

18th July 2010, 21:28

havent drove a standard gti/vts in ages lol

would i hear any noise from the valve catching?(if still bent)

18th July 2010, 21:28

Yes, depends which valve it is. Inlet or exhaust. If either are bent on the compression stroke it will be blowing back out the valve. So detonating up through the inlet or out the exhaust. If it is bent badly then, depending on how stiff the springs are it could damage the collets dropping the valve. All sorts of bad shit really. The list could go on
So yes the power would be limited and the will be noticeable and rhythmic

18th July 2010, 21:35

mine had a slight misfire

18th July 2010, 21:53

ok
if a headgasket had gone between 1 and 2
would this create a missfire at all?

18th July 2010, 21:56

Quote:

Originally Posted by Aaron

ok
if a headgasket had gone between 1 and 2
would this create a missfire at all?

I'd say so, yeah.

A mate's VTS had the timing belt jump a tooth or two - the engine ran with a misfire, but had bent valves IIRC.

Either way, it sounds like your mate will have a head re-build on his hands at the very least.

18th July 2010, 22:03

I'd be very surprised if it ran at all with 16 bent valves.

Get a compression test done before buying, you can do it yourself, only takes a few minutes and will tell you a lot

18th July 2010, 22:04

Quote:

Originally Posted by Aaron

ok
if a headgasket had gone between 1 and 2
would this create a missfire at all?

most definately, just changed the head gasket on an S that had blown between 2 pots, best way to confirm thats the problem is a compression test

18th July 2010, 22:04

he has bought it yet.
hes planning on buying it.

rang the guy
he said
Well i bought it with the headgasket bust
so i fitted new headgasket with cambelt/tensioners/aux/waterpump.
so ill be able to see if thats been done and if so then should be all ok.

compression test eh.
wher can i get the kit from?

what psi will i be looking for?across all four pistons?
how do you perfom a test on a 16v engine?

18th July 2010, 22:06

+1 to rauchz, 16 valves bent= zero compression. if they are all bent it'll crank over bloody quick on the starter lol

18th July 2010, 22:06

if he's just done the hg, then I'd say either the timing is off, or the hg is fitted incorrectly/headbolts not torqued up properly.

I'd budget for a cambelt kit, headgasket kit, and then fluids too, ontop of the cost of the car

18th July 2010, 22:10

Put it this way - I'd 99% say the head needs to come back off, but a compression test would confirm this. So, with the head off, you can then see if valves are bent and fix it depending on the problem.

18th July 2010, 22:11

compression testers are cheap enough, approx £10 for DIY one on eblag, remove spark plugs, screw tester into each plug hole in turn, crank over and record reading. approx 150psi across all 4 pots is ok, the one we just did was 145,30,30,150. Guess where the gasket had split?

18th July 2010, 22:11

think you getting the wrong idea?
he has done all the work the new owner now selling.

but my friend has heard from a lad wher he lives that about 6 months ago he was told it had a bent valve(i think one bent valve)
so my friend will be buying it apparently fixed

18th July 2010, 22:13

so does the car run fine or not?

has it got bent valves now or just hearsay that it 'bent a valve' 6 months ago ? Did it bend 16 valves ?

Had it just had a new headgasket? why was this done, because of the bent valve?

I hope im not the only one that is confused - we're just trying to help your friend

18th July 2010, 22:14

If your friend is going to buy it fixed, then any sort of misfire when your friend drives it and it's not been fixed so he shouldn't buy it

18th July 2010, 22:19

right ill explain again lol
no i can understand your confusion.

the car is for sale
according to the new owner.
its running mint
its had a new HG,cambelt,pump,aux etc.

so my friend wants to buy it.
He told his friend he was buying it and his friend says theres a thread about it on 106 oc. so he checked and saw im selling my car because one of the valves is bent and not running well.(this was about 6 months ago)

by this time the new owner has bought it and done all the above
But i askd about the valve and he said "they looked fine when changing HG" and didnt know anything about a apparent bent valve.

It wasnt 16v bent valves
I mean 16v (new sentance), bent valves but runnning fine. not all together so for this.
i dont do writing anymore lol

ill do a compression test to make sure.
are they all the same?the kits..

18th July 2010, 22:22

yeh, compression test it and ask for receipts for the recent hg/cambelt etc.

compare the compression test results across 4 cylinders, and then repeat with a teaspoon of oil dropped into the cylinder bore. Compare across the cylinders, and the difference between dry, and with oil in it.

This'll give you a rough idea as the the ring condition and whether any valves are bent. Post up the results on here if you want a second opinion.

People chat rubbish sometimes, so someone saying the valve is bent 6months ago might just be a shite diagnosis by him so I wouldn't take that as the truth without proof.

If you drive it, you'll know if it's misfiring. If it drives fine and misfires occasionally then clearly a valve isn't bent. Might be the coilpack or injector fault.

18th July 2010, 22:22

Can borrow my tester if you fetch/ bring it back

18th July 2010, 22:27

olly sent you a cheeky text...

ok will i notice a difference between a bent valve missfire and a icv/coilpack missfire?

what reading should i be getting on all four pistons?
ill just do a normal test. didnt really want to be doing the wet one?

18th July 2010, 22:30

Quote:

Originally Posted by Aaron

olly sent you a cheeky text...

ok will i notice a difference between a bent valve missfire and a icv/coilpack missfire?

what reading should i be getting on all four pistons?
ill just do a normal test. didnt really want to be doing the wet one?

Well upto you really, I'd do a wet one if I was looking to buy it and was doing a compression test anyway.

Well I'd expect a bent valve misfire to be constant, whereas a coilpack misfire might be intermittent.

reading wise it can vary but around the 180-200psi mark isn't unknown - you're more interested in the difference in psi between cylinders.