Any Guesses What I've Broken?

[Pugly 1]

Hi all, first proper post on here.

 

Did my first full trackday in my 1.6 GTI on Sunday - I bought the car already converted to a track/race car. Engine has reportedly been balanced, fitted with twin Weber 40's and head ported and polished.

 

Ran like a sewing machine all day until the last 30 mins of the session. Suspect the engine has eaten a small stone kicked up by the car in front and has got in through a hole in the airbox (which was noted just before heading out but decided it would be ok as a small hole that was well hidden behind other more solid things - error!).

 

There was a rattle for a second or two followed by an (involuntary) rise in engine RPM at which point I hit the kill switches and coasted to a stop. Smoke coming from oil breather.

 

I am not a mechanic but willing to try my hand at most things - does anyone have any suggestions what I've broken and where to start? I was planning on taking the head off and having a poke around but not sure what I am likely to find. What are the chances of a knackered piston if a valve has bent?

 

Cheers,

 

Matt

[Slo 283 1 Cars]

Unlikely to have damaged a piston, however in my experience any piston to valve contact usually results in not only bent valves but also a snapped timing belt or the woodruff key snapping off the camshaft pulley. Does it start?

[Pugly 1]

Unlikely to have damaged a piston, however in my experience any piston to valve contact usually results in not only bent valves but also a snapped timing belt or the woodruff key snapping off the camshaft pulley. Does it start?

 

That sounds like good news (I think!) - yes it does start, we tried it briefly after being towed back to the pits and it ran but sounded very rough (possibly only running on 3) so knocked it off pretty much straight away.

[Tom Fenton 1,526]

First off remove the spark plugs and see if it will turn over using a spanner on the crank pulley bolt. If it does 4 revolutions of the crank without any stiffness, then the next step is to do a compression test (Google for more info if you are not sure).

If that checks out ok then put the plugs back and try to start it.

[Slo 283 1 Cars]

When you say rough running do you mean misfiring or missing or general lumpyness or is there mechanical noises?

 

And as above a compression test is a must to determine if you need to pull the head off to look.

 

If it has sucked in a stone i'd be inclined to take of the inlet manifold to have a peek in the inlets.

[scbond 15 1 Cars]

To be honest, I can't see a stone being able to get in through the airbox. If, by incredible odds, one did get through the hole in the airbox, it would then need to get through the filter. You can very quickly rule that one out by checking the filter to see if there's a noticeable hole in it, but it's unlikely I would've thought.

[Pugly 1]

When you say rough running do you mean misfiring or missing or general lumpyness or is there mechanical noises?

 

And as above a compression test is a must to determine if you need to pull the head off to look.

 

If it has sucked in a stone i'd be inclined to take of the inlet manifold to have a peek in the inlets.

 

It sounded like it was only running on 3 and very rattly - I can't be sure as it was only run for a brief time as it really didn't sound good! I had a GoPro running at the point when things started to go wrong (but not the start up afterwards) so I will check the video for any clues and upload it to YouTube for a more expert ear to have a listen.

 

I've borrowed a compression tester so will try hand cranking it and doing the compression test this weekend (away for the rest of the week).

 

To be honest, I can't see a stone being able to get in through the airbox. If, by incredible odds, one did get through the hole in the airbox, it would then need to get through the filter. You can very quickly rule that one out by checking the filter to see if there's a noticeable hole in it, but it's unlikely I would've thought.

 

The filter itself is fine - the air intake on this car is a hose routed down to the fog light with a filter just before it opens up into the plastic airbox covering the carbs. I am thinking some foreign object has got in because there is a hole (That shouldn't be there) in the airbox directly in front of one of the trumpets on the carb (not sure of the correct term) after the filter. I'm at work at the moment but I'll upload a picture later on that shows what I mean.

 

 

 

Thankyou to everyone for your help!

Edited July 8, 2014 by Pugly

[Pugly 1]

Just managed to squeeze in a bit of time on the car.

 

To answer the question of how something got in past the air filter, the hole in the airbox can be seen below:

 

 

The missing piece was sat inside the airbox wedged in between the foam seal and the bottom of the mounting bracket for the air box. The missing piece fits perfectly in the hole so it's not a piece of plastic that's gone in.

 

I removed the spark plugs and found this on cylinder 2 (Looking from the front of the car, left to right) which whilst not immediately in front of the hole in the airbox, is still close enough to suggest that something found its way in through the hole and into the engine proper.

 

 

I tried hand cranking the engine but as expected from the state of the plug, it went stiff.

 

So, head off this weekend to have a look at the valves!

[Slo 283 1 Cars]

That does look like something went in but it probably sounded like it was running on 3 afterwards because the spark plug gap is shorted out. If there's anything in there its more than likely killed the valves.

[2052NV 24]

That kind of looks like a valve has dropped, or the head of the valve has snapped off. What were the reults of the leak down?

[Pugly 1]

As an update to this topic...

 

 

 

I think the technical term is, that's buggered!

Edited November 15, 2014 by Pugly

[Anthony 1,000]

Yup, you broke that good and proper!

[Alastairh 47]

Good effort!

[omega 82]

so did it get in through the air box or was it something else ?

[calvinhorse 870]

Daaaaaamn

 

Looks like the damaged airbox was a red herring, valve has snapper off by the look of it!

 

Does the airbox go to a cone filter? I like the look of it, bet it keeps the noise down for track days

[Pugly 1]

In all honesty I am not sure if the damage was caused by FOD or not. I have the moment it broke on GoPro footage and there is definitely a few bits from the edge of the track kicked up by the car in front and a rattle which makes me think there was something ingested but then during the strip down yesterday I couldn't see anything that had got in (But as can be seen, there's a lot of mangled metal!).

 

Yep the airbox does go to a cone filter - cold air is fed in from a feed by the O/S driving light, through ducting and the filter and then into the airbox. It is quite a neat setup and I had no problems with noise regs.

 

On the up side - opportunity for more power. Hopefully a 1.9 engine going in this week with a few nice bits fitted. Was tempted by a 16v of some sort but it's only for trackdays so don't need the extra power and can use my existing ancillaries on a 1.9.

[2052NV 24]

I was bang on! Id say that the valve has failed more so than a forign object entering the intake..

[Slo 283 1 Cars]

have you taken the sump off yet to see whats inside?