[rhauff]

I went to start it the other day, it cranked a couple time & I thought it started, but was quiet when I let off the key. Cranked again & it sounded like no compression & starter running fast or starter not engaging.(it was engaging)

Checked timing belt, it is on and cams are in time. The odd thing was, the belt WAS loose. Pulled plugs and cranked to do compression test on a couple cylinders, got 90 & 40. Timing belt is now tight. Probable sticking tensioner -- Must replace.
Now, did leakdown test & all 6 cylinders have a leak out intake or exhaust or both. Check with borescope, can't see any valve collisions with piston.

What's going on?? What are the odds of timing belt jumping 360 degrees on crank & going right back to home??? Impossible.

Car is 2003 4-mo wagon with 208k miles, belt & tensioner where replaced at 140K and it has run perfect the whole time. No codes showing.

 

[ylwagon]

Belt was loose, then got tight again? Was it loose when cold or hot? That seems odd, unless your area is really cold, and the tensioner didn't move as the engine contracted. My old 12-valve 2.8 did not have an automatic tensioner. Once you set the belt tension, that was it. I found that the tension was different between a hot and cold engine; it would tighten up when hot, presumably because the sprockets all moved slightly apart. My habit with that motor was to set the tension when warm/hot.

 

[rhauff]

Car was cold, parked in garage overnight, probably about 45F. It has the automatic hydraulically-dampened tensioner.

 

[Tomvw]

I suggest you remove the VCs and check the intake cam timing.
Check the timing marks, the 16 roller count, and check the condition of the 4 CCT pads.

 

[rhauff]

Got the valve covers off, here's the left head:

Right head:

Bank 1 Exhaust cam:

Bank 1 Intake cam:

Bank 2 Intake cam:

Bank 2 Exhaust cam (Appears off a little due to parallax):

Crank position is perfectly aligned on mark. I'm not sure what you mean by 16 roller count. I only see 2 CCT pads, they are fine. While turning the crank around CW, the cam chain tensioners move up and down and I hear oil suction'y sounds, is that normal? Oil level is full on dipstick.

 

[rhauff]

Ok, found info on the 16 roller count. Bank 1 is exactly 16 rollers. Bank 2 has cam chain tensioner down when crank is at TDC so there is a little less chain between the cams. Measures about 15.5 rollers.

I placed a feeler gauge between cams (that were off lobe) and the lifter/bucket. Have no measurable clearance, I tried down to 1 mil. Should there be clearance?

Seems to me if the valves were truly bent, there would be quite a bit of clearance.

 

[rhauff]

Just checked bank 2 again. Because the CCT is down, it causes the exhaust cam to be rotated a little more CW, and hard to get a straight on view due to coolant hoses in the way. It IS 16 rollers between the cam marks.

 

[Tomvw]

There are 4 pads, 2 are under the CCTs.

It should NOT be 16 rollers BETWEEN the marks.
NOTE: Haynes incorrectly states and shows "16 rollers between timing marks"
After some research, I have discovered that some of this wiki.ross-tech info is also incorrect,
the V6 Bank 1 timing is the same as the 1.8; NOT as shown in the diagram.
See the images at the bottom of this page: 16730/P0346 - Ross-Tech Wiki
Note offsets.

See post #6 in this thread: http://www.passatworld.com/forums/volkswagen-passat-b5-discussion/525434-2-8-30v-timing-help.html


If all cylinders have excessive valve leakage, you need to remove both heads and re-build them.


When you refit the heads I suggest you replace the following:
A) Timing Belt
B) TB Tensioner Damper
C) TB Tensioner Roller
D) TB Idler Roller
E) Water Pump & Gasket
F) Thermostat & "O" Ring & maybe the Housing

Also consider replacing:
G) Serpentine (Accessory) belt
H) Serpentine belt Tensioner
I) Check all coolant hoses, replace if required
J) Coolant

 

[rhauff]

Yes, that Rosstech diagran is what I used earlier I have 16 rollers from cam to cam. I re-did the leakdown test, last time some of the cylinders were at the top of exhaust stroke & it appears the intake valves begin to open. This time all 6 were at the top of compression stroke, and it looks like all the leakage is out the exhaust valves.

So the big mystery is still -- What kind of catastophic thing could cause the exhaust valves to start leaking while I was starting it?

 

[Tomvw]

The only things that could suddenly cause the symptoms you have described would be retarded valve timing, this would bend exhaust valves.
Or advanced valve timing, this would bend intake valves. This could have been caused by a failed TB tensioner.

DO NOT crank the engine before replacing the TB Tensioner.
I suggest you replace the TB tensioner and tensioner pulley.
Then remove all plugs and do a compression test on all cylinders.

 

[zmaninco]

I have this scenario twice before. The car almost started but did not. Gas cleaned the cylinder walls and the car did not start so no oil in the cylinder walls are washed and hence you have no compression. Pull the spark plugs, squirt some oil in each one, then crank it. It will take about 30 seconds but the engine will catch slowly with a couple cylinders and then others will follow. After running poorly for about 15 seconds the others will catch and you will be back.

This is true. I have seen it twice.

Z