My Blown Up Engine :(

[kate205gti 4]

took my car to emerald yesterday to get the new gti-6 engine mapped on the rollers..

 

drove up there lovely, everything seemed fine got it on and started the mapping, working up through the rev range, got to 3k then one second as dave was bringing the revs up and it dropped to 3 cylinders

 

checked the leads and cylinder 2 was not firing - although the lead was sparking on the coilpack - so compression tested it and showed 50 on cylinder 2

 

got RAC'd back and have got the engine out and stripped already, but cant really see anything it looks just a tiny chip out of the edge of one of the pistons

 

there was some slight pitting near the valves:

 

but would this have caused the cylinder to lose all compression?? doesnt look anything major

 

what do i need to do to fix it??

[maturin23 10]

Christ you don't have much luck!

[sorr 0]

Since you have the head off turn over the cam shafts and check that the valves on that cylinder are closing correctly. Given the bore does not look 'torn' up the head is where I would look.

[d-9 0]

Cant really tell in the pic, does the chip in the piston look fresh or is it sooted up? If its sooted up it might be an old damage from when the cambelt snapped in the past (assuming a lot here!)

[Toddy 7]

Could be:

 

Has the belt and tensioners been replaced?

 

Valve to piston contact, Did DW set the lift at TDC or did you rely on the timing holes. (the bottom pulley may have gone out of synce due to it been bonded together using rubber therefore the timing was set incorrectly).

 

The picture is not very clear, can you see where the valves have touched the pistons?

 

You need to take it to a machine shop so that they can test the valves for straightness, also worth checking the guides since the head is in bits.

 

Toddy

[kate205gti 4]

replaced cambelt and waterpump and fitted S16 tensioners before it went in didnt open it up then as it was apparantly a low miler

 

anthony timed the engine up for me using a dial gauge

 

the valves dont appear to have touhced anything (no nicks/marks - they all still carbon coated) and theres no obvious sign of damage to the head apart from the slight marks

 

there was a bit of grit in there, will check the piston later but i think it was carbon coated too? so may have been an old chip?

[Anthony 1,002]

Has the belt and tensioners been replaced?

 

Valve to piston contact, Did DW set the lift at TDC or did you rely on the timing holes. (the bottom pulley may have gone out of synce due to it been bonded together using rubber therefore the timing was set incorrectly).

Cambelt, tensioners and waterpump were done less than 500 miles ago.

 

Cams were timed in using the TDC method by me, as like you say, the bottom pulley had slipped. Valve clearance was checked after timing them in and was OK, so unless the vernier slipped (which given it's only one cylinder that's dropped compression seems very unlikely) I wouldn't say it's related to cam timing.

 

The impact damage to the head looks to be fresh so there's clearly been something bouncing around inside the chamber, and with visable damage to the edge of the piston I'm hazarding a guess that the piston has cracked/broken on the ring lands but I can't tell from that photo. Either that, or it's sucked in some foreign matter, but I would have thought that the dyno room at Emerald should be fairly clean. Not quite sure how much damage to the ring lands you'd need to lose circa 150psi or compression though, and certainly I've suggested to Kate that the valves on that cylinder are all removed and checked for straightness and the seats for damage/cracking as a matter of course.

[Sandy 191]

I don't know what the answer is, but it's certainly shat luck.

 

Valve straightness can be checked quickly and easily by trying to lap it into the seat, then inspecting it to see if the ground area goes all the way around the valve or not. Another slightly back street method, is to tap it with a hammer, a valve that's firmly in the seat sounds different to one that isn't. But i'm not keen on hammering engine parts if there's an alternative.

Edited July 26, 2007 by sandy309

[BuD 0]

From what I have read if the valves were not straight you would expect the engine to have tapped.

 

Make sure you repace the guides if you disturb the valves as not doing so leads to them tapping when rebuilt.

 

Terrible luck - hope you get it sorted.

Edited July 26, 2007 by BuD

[C_W 3 1 Cars]

Kate, I can't believe your luck with 16 valve engines! maybe your only way to reliably run 16 of them is to run two 8 engines!

[Batfink 201]

the answer is get a honda

I can't beleive your luck with engines. Did you drive it to FCS without any mapping done? Could it have been running too lean or something to cause piston failure. (Probably not but just banding ideas around)

Maybe time to go 8v! I thinkk I might know of a 220bhp 8v race engine but it might be sold by now....

[kate205gti 4]

was running too rich (deliberately) and only did about 160 miles at mincing speed

 

what can i do tonight to test it? will try duck oil in the upsidedown cylinder head - anything else??

[Mikey S 29 1 Cars]

its a shame you have taken the head off. i would have done a cylinder leakage test before removing it as it would of given you an pretty good idea of whats happened in there. is it just the angle of your first photo as that exhaust valve looks bent to me?

[mattmk1 0]

Close the valves in turn and pour a little petrol into the inlet/exhaust ports. If the petrol seeps past the closed valve, then it is either bent or very badly seated.

[28CRAIG 2]

I would check the head see if the valves are sealing o.k and get some pistons for it then feed Anthony some kfc and all fixed.

 

Or swap engines with Alastair when he's not looking

[Sam 4]

How did the gasket look? Not sure if you mentioned it in the thread or not. I've had this before, everything checked out buy I'd just used a crap head gasket that burnt between cylinders slightly.

[Sandy 191]

Close the valves in turn and pour a little petrol into the inlet/exhaust ports. If the petrol seeps past the closed valve, then it is either bent or very badly seated.

This method has failed me in the past, it was only when I tried to grind the valves in that it was clear they were bent.

[James_R 3]

When we took the engine apart there was some debris in cyl, which you can see did the damage to the chamber, it's minor, but it's wether it was sucked in or a fragment of piston 2.

 

Since the bottom end's been sat it's had oil in the bores which hasn't gone down at all indicating goodring seal, so next port of call will be stripping the valves out of cyl 2 and seeing if they lap.

 

Past that think we're a bit stuck unless it was the debris holding the valves open slightly.

 

[Alastairh 47]

What did the plugs look like?

 

Soo unlucky

[Richie-Van-GTi 71 2 Cars]

When we took the engine apart there was some debris in cyl, which you can see did the damage to the chamber, it's minor, but it's wether it was sucked in or a fragment of piston 2.

 

Since the bottom end's been sat it's had oil in the bores which hasn't gone down at all indicating goodring seal, so next port of call will be stripping the valves out of cyl 2 and seeing if they lap.

 

Past that think we're a bit stuck unless it was the debris holding the valves open slightly.

 

 

 

surely good news then as worst case now has to be new valves. Id be tempted to have the head presure tested and a light skim while its off just to rule the head out as well.

[Guest Frittjoff]

im guessing something has either got loose on the way into the engine or a fragment has loosen from the piston / rings

as you lost compression i would check the state of the rings if there whole and any dent/marks in the bore, the valves look fine no colour change witch would mean a leak.

[smighall 1]

The head will almost certainly need a skim anyway. The GTI6 head always seems to slightly warp when you take it off, even following the bolt removal pattern.

[Beastie 1]

Has the engine had new rings in the recent past? It's not uncommon for a new top ring to hit the wear ridge in the top of the bore and break with a resulting fragment of ring punching through the top ring land and hammering against the cylinder head (I have a Healey 3000 engine in the workshop right now suffering from just this as it happens)

[James_R 3]

pistons look intacted. if the head if fine then will be time to pull the pistons out, trying to do it one step at a time rather than pull everything down and have to spend more putting it back when it wasn't needed.

 

Looks to be debris sucked in, bit it's wether it's damaged the piston or not, bores etc.. are all fine.

 

Oh and no sign of valve/piston contact at all

[kate205gti 4]

took the valves out yesterday and lapped them back in and theyre fine (thanks james!) so looks like its time to take the piston out now

 

anyone got a good spare gti-6 piston for sale??