Did complete timing belt job on B5 A4 2.8 12V. After 2x 10 min idling warm up, belt broke. Tension to high (stupid 'tension until you barely can twist belt 90 degree').

I have decent instructions for the timing belt job, but they are based on the engine already being properly timed. I know need to do a ground up timing (obviously, with the belt broken, crank and 2 cams are not timed anymore).

Can someone quickly sent or link me to good, detailed instructions?

Cams and crank turn smoothly, so I have still hopes I did not damage the valves. Compression test (after timing) will tell, I guess.

Thanks.

 

It really isn't a whole lot different. My experience is on the 2.8 but the 1.8 shouldn't be much different. All you will need to do is pull the valve cover to see the cam timing marks. There are little notches on the cams that you will want facing up. There is an arrow that they should line up with. Now get the engine to TDC and proceed from there. I will look at my Bently manual tonight and see if there is anything else.

 

I have the 2.8, 12V.
Front timing covers are off, so is crank pulley, serpentine tensioner. Fan is still on, but I can take off. What else?

Valve covers have to come off to see the marks?

I have the software Bentley (unfortunately, a big PAIN to use with the 'virtual machine' crap); will check there.

If you come across good link, please send.

Thanks.

 

I just realized: the cam sprockets have the oval plate with large/small hole, which is indexed to the cam itself. So having both larger holes facing inwards, horizontally (I still have the cam locking tool that goes into the 2x2 holes) should put the cams in the right position. Then crank to TDC (but this time, I need to go through the TDC process (?) to ensure REAL TDC (not 180 offset) without the aid of verifying that the larger cam holes are inwards.

Haynes says to use compression gauge for cyl 1, with TDC approaching (clockwise turning) should show compression on cyl 1. If not, cyl 1 was on exhaust stoke, turn 360 degree.

Can't use a feeler in the spark plug hole to find high point of piston, huh? (because TDC could be either compression or exhaust stroke).

 

Long as the cams are indexed, that's all that matters. A piston at TDC is a piston at TDC. It's the cams that matter in indexing the engine dunce with a piston at TDC, the cams could either have the valves closed (compression stroke) or the exhaust valves open (exhaust stroke). The cams are what need indexing, which you've done. Put the crank pulley on, rotate SLOWLY until the timing mark lines up (listen for valve interference during the rotation), and put the new belt on.

 

I guess that is why they suggest the compression gauge on cyl 1, to determine compression stroke (not exhaust stroke) to find real TDC. Feeler would only tell that piston is 'up'.

Will get Autozone gauge, needed anyway for compression test when timing is done again.

 

That's if the belt is on and you're setting up the car to tear down the timing system. The crank really can't be 360 degrees out of phase. If you align the crank pulley timing mark with the pointer on the lower timing cover you WILL be set up correctly. You already have the cams set via the oval brackets - line up the crank and you're good. Lining up the crank and then turning it 360 degrees would simply put it right back in the position it was in - there is no difference in rotational position for the crank with respect to the cams.

I agree though - get the gauge. you're right that you'll want it to check compression after the car is reassembled.

 

id the timing.
Compression test (slow cranking battery, weaker first to last cyl; compression tester NOT screwed in very tight, since darn O'Reilly hose slips on connector and can't get adapter in plug hole out easily):

Cyl 1-3 (pass side front to back):

90, 90, 100

Cyly 6-4-5 (driver side front to back):
80, 80, 90

Previously: front 2 on both sides: 120, rear on both sides: 150 (with faster crank and tight gauge/adapter).

Since all 6 reading are in the 90 range (low, but considering the circumstances), does it mean valves are closing, are not bent?
What would I expect to see if valve is bent. Really low (like 10 or 20)?

Time to try test starting the car?

 

Engine start/runs fine. Brief test start only, no coolant etc.


Engine test fired and run (briefly only, since no coolant etc. hooked up).

Rechecked tension (2 finger 90 twist) and set a bit lower (got burnt ones) and timing.

Once concern:

The holes on the oval index are NOT perfectly horizontal (within the play of the cam lock tool).

See the deviation from horizontal below, also difference between non horizontal (right on TDC mark) and horizontal (1/8 inch off mark).

Is it off by one tooth? Should I try to get both perfectly horizontal (without possibly sloppy cam lock tool)?

With the passenger side horizontal and crank on TDC mark:


Driver size NOT perfectly horizontal, TDC:


Position of driver cam not horizontal, TDC:


Position of driver cam horizontal, but NOT TDC mark:


Amount of diviation from TDC:

 

All back together, ran short warm up (less than 5 min). Eninge sound good.

Due to the slight offset (1/2 belt tooth) on the driver side, I decided to take the valve covers off and check the EXACT cam timing. There is supposed to be a timing mark.

Does anyone have a photo or sketch showing the marks and how ot use them?

I will post current situation. What are the 'allowable' tolerances?

If not good enough, I plan to wait for the new belt (in the mail), install and then do a "manual" timing (crank in exact TDC, cam bolts loosened, position each cam to exact timing mark).

Then:
- reliable (mine was not) compression test (dry), compare with numbers taken before timing belt job
- wet compression test (to find out if possible low compression is cyl/piston/ring related or valve/gasket)
- leak down test (further narrow down possible causes for low compression)