T5 CFCA: Timing Belt Jumped - Causes & Fixes

I have a T5 where the V-belt disintegrated and the timing belt jumped a tooth. I adjusted the timing using the elongated holes and it started, but it sounds like there's no compression.
I then performed a leak test. Cylinder 1 showed a 28% leak, but I didn't hear anything coming from the turbo (DPF was removed) or the intake manifold, just a little bit from the oil filler cap. Cylinder 2 showed 10%, cylinder 3 showed 16%, and cylinder 4 showed 12%. I also measured the compression, but it was less than 5 bar in all cylinders. After removing the valve cover, I saw that the rocker arms on cylinders 3 and 4 were broken. All the others seem to be okay.
"There are factory-installed camshafts. How can I check if the camshaft lobes have twisted? Also, I'm concerned about the endoscopic image of the first piston."
You can see valve marks on every piston, but the first cylinder is full of oil (carbon).

Hello,

Unfortunately, I can't provide any information regarding your questions. However, based on the observed damage, I would recommend checking whether all the pistons are still reaching the top dead center (TDC) and whether any of the connecting rods might be bent.
It is possible that one or more valves are now stuck in the guides and are therefore not closing properly.

Best regards, Rainer.

Hello!

So, you're going to have to remove the cylinder head anyway.

If the valves are open, they are also crooked.

And then we'll see what happens next.
You'll get that cylinder head working again.

But the oil-soaked cylinder is what worries me more.
If the piston is broken, it usually doesn't make sense to repair it anymore.
Furthermore, there's always the risk that the crank mechanism is damaged.

I wouldn't invest a lot of money in that.

Hello,

I completely agree with Rainer and Steffen, definitely focus on the top end. Measure the piston-to-seal clearance. Remove the oil pan and check the upper bearing shells of the connecting rods; if the connecting rods aren't bent, then at least the upper bearing shells are definitely worn. Also, when checking the broken rocker arms, inspect the lifters and their seats in the cylinder head.


Regards, Mpire.

"Without a proper pressure regulator, nothing works here; the valves are 99.99% defective."

Check the piston protrusion. If everything looks okay, I would leave the lower engine components alone. In my experience as a mechanic, I've dealt with several broken or jumped timing belts, and the lower engine components have never been affected.

One should investigate the cause of the skipped timing belt.

Hi!

Take a look at the piston in the second photo.
Is there a crack visible on the left?
It looks a bit strange to me.

Actually, I'm still not entirely sure why the cylinder is so oily.

Okay, I've tilted my head down now. In the live view, the oil buildup doesn't look as extreme as it does in the endoscope camera. All the cylinders look pretty much the same. I haven't examined the pistons closely yet, but I don't see any cracks in the photo.
It would be a complete disaster, because the valve guides are also extremely worn.

Hi!
Well, I guess I saw the edges of the oil-based crust.

You can let me know how things progress.

I will do that. I'm currently having valve guides installed.

Hello.

Here's a practical tip for crack testing:

We always used a square aluminum plate with 4 holes for the head screws, and a rubber mat underneath. It was screwed onto the top of each cylinder. The plate had an air pressure connection in the center.
Turn the piston upside down on a vise, fill the combustion chamber with brake cleaner, and then press it down. If there's a crack, the liquid will leak out through it; if not, it will remain inside.
You then do that from cylinder to cylinder. It has always worked well.


Regards, Mpire.

It would probably also work with gasoline.
hg
Herbert.

Hi!

This is also a good method for pressing the plate.

But after seeing the new image, I don't think there's a crack in the piston anymore.
Those were more likely to be edges of carbon deposits that I saw in the image from the endoscope.

But even so, the cylinder looked somewhat oily.
I was really shocked when I saw the picture.

Of course, it's still possible to push the cylinder out using a plate and a rubber pad.

If there's a problem with the piston rings, you can often tell because air will leak out of the crankcase from one cylinder, while the other cylinders don't have the same issue, or have it to a much lesser extent.

It's running again.
I only had the cylinder head repaired.
The idle injection deviations look good, around +/- 0.2-0.3 mg/H.

Congratulations! May Möller endure!