I don’t mind admitting this one has me completely stumped.

Brief history, low mileage car/engine with fully reconditioned head which I fitted sometime in April 16, since then the engine has never been 100% at tick-over with a slight wobble but not a miss.

At the time I had concerns when setting up the cam timing due to not being able to get exact TDC reported here, this I put down to chain stretch (as per thread) as I tried both tooth positions either side of TDC settling for the one shown.

Pic of final set-up showing 5 degrees or so ATDC



E300D timing chain stretch

After the rebuild compression figures looked like this with probably wet bores from assembly (please see follow-up post, as these figures may have been achieved using 14 BTDC configuration).

Cylinder bar

1 26
2 25
3 22
4 27
5 25
6 27

Since the rebuild I have carried out another compression (about six months ago) test followed by two this week

The figures from six months ago showed a significant drop but not as bad as the first set this week below, cylinder 3 and 4 have actually failed as per MB spec hence the decision to pull head.

Figures this week, timing still set as above

Cylinder bar

1 21
2 19
3 16
4 16
5 19
6 19


The compression tests this week showed a huge amount of oily carbon build up not only on the injector faces but also caking the heat shields across all six, oil was also seeping heavily out of breather pipes indicating blow by, smell of burnt oil was strong too.

As the compression test this week revealed a fail on cylinders 3 and 4, I immediately thought the timing is out clipping some of the inlet and exhaust valves, perhaps some worse than others due to variations on compression results, this was the only thing that seemed to make sense given the oily build up. So, out comes the parts list for a replacement head, parts ordered including dial gauge to make sure TDC is correct and the pointer hasn’t been moved during a water pump overhaul, however after reading another thread where the chap zip tied cam sprockets (same as my approach) but had an almost identical issue (loss of compression but resolved by moving cam timing),

Post 2

606 head removal

I thought give it a try, after all nothing to lose lose as swapping out head anyway, results are below.

Cylinder bar

1. 24
2. 27
3. 24
4. 22
5. 28
6. 22


Well there's a surprise similar to that experienced by the poster above, cylinders 3 and 4 are now well into spec but the problem is crank marker reads roughly 14 degrees BTC



So in summary, I have two settings, one ATDC and one BTDC both of which give different compression readings on different cylinders, returning duds to almost new pressure. Is there anything in-between, another adjustment perhaps, would moving the chain on crank sprocket as opposed to cam sprocket make any difference (clutching at straws here) ?

Not sure whether to pull head or not, over to you guys

__________________
David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)