Camshaft alignment on VW 1.8 20v?

Question

After my breakdown 2 weeks ago, I have finally got round to looking at it today. (tapping sound from engine, then nothing, and turned over as if there was no compression, I havent done a compression test yet, but will do one tomorrow.)

Took off the cam cover, and aligment between the crank and exhaust cam is fine.No visible damage at all on the cambelt, and looks to be in good condition. Now, the inlet camshaft is driven by a chain off the far end of the exhaust camshaft. I have no idea how to check if this has jumped a few teeth. The manual I have seen says to mark the cams before disaasembly, and give no clue to their alignment to each other if you are fitting new cams, or checking their relative postions.

Does anyone have this data?

I have had a quick look at the cams, and they dont appear to have a visible mark of any sort, other than a bit of paint, which looks like it was done by me last time they came off.

Ta Alan.

Duncan Wood · Accepted Answer

Mrcheerful · Answer

if the other cam is still turning then it is unlikely that it has skipped teeth on a chain. If it all seems to be turning normally, yet has no compression then the next thing is to find out where the compression is going. In the workshop I would attach an airline to each cylinder in turn with that cylinder turned to tdc on compression, you can then hear where the air is blowing out of. I assume that it is a turbo engine? if the turbo breaks up it can put bits through the engine.

reg · Answer

ive done one of these but i did it on the bench, you will need the tool to compress the hydraulic chain tensioner.try this link  for a pic not sure how clear it'll be you might have to zoom in

A.Lee · Answer

Thanks, I can make it out now when looking this morning. I've found a problem, though maybe not the cause of the breakdown, the timing looked right to me last night, but upon seeing the pics, I realised the cams were 180 degree out. That's strange. So did a lot more testing, and found they were

180degrees and about 4 teeth out. Stripped down more, and found the camshaft drive cog had sheared its woodruff key. That seems rather bizarre, especially as the bolt holding it on was really tight too. So either the shearing woodruff key has caused the fault, or the water pump, or possiibly a dropped valve had temporarily jammed the top end gear when starting up. Either way, it looks like I'll need to take the head off to see if it is worth saving. There was definitely a rattling in the 10 seconds it ran for, so probably the valves hitting the pistons. I dont think it would be worthwhile fitting a new key, re-timing it, then trying a compression test, though I have access to a diver tank, so could try each cylinder in turn, with valve closed on that cylinder to see if there is any noticeable leaking through unseated valves, though having never done it before, it'd be guesswork.

Ta Alan,.

A.Lee · Answer

.....Head now off.11 valves visibly bent, possibly 3 others too.No apparent cause, other than the sheared woodruff key in thecambelt/camshaft drive cog.Rather annoying.Alan.

Nige · Answer

Something has caused it to shear on that shaft, as in that shaft stopped for some reason, or the key was very weak.

Mrcheerful · Answer

or the bolt was loose or was not renewed/loctited/fitted right when it was last apart.

A.Lee · Answer

It was really tight. I read a piece this afternoon from a Company in the US who supply a modified drive cog, held on with both the woodruff key and a dowel, as well as the bolt. They say it is a known weak part of this engine, though it is the first time I have read it. Alan.

Chris Bartram · Answer

Pisser. Is the engine saveable at all, or does that write it off?

Mrcheerful · Answer

Overtightening can cause failure due to distortion, which is why it is important to use correct techniques (mainly holding method and tightening method in this case)

A.Lee · Answer

Probably just about worth saving.£350 ish for parts and associated consumables. If it was £500+, then Idont think I would bother. A day to put it all back together. My work is really quiet duringJanuary, so I should be able to fit it in.The car is in reasonable condition, so if running would be worth£1000-1500.Alan.

Camshaft alignment on VW 1.8 20v?

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