Rod bearings

[QuickTD]

I've been hearing a light tapping on light/neutral throttle and vibration felt in the clutch pedal for awhile now so last oil change I decided to pull the pan and have a look. This is what I found



All the bearings had some fatigue damage. No real wear to speak of, just bits of bearing overlay flaking off. No damage to the crank and the journals are perfect (both size and eccentricity) This is my daily driver and has 230000km on it. Pump has been turned up quite a bit, aneroid pin from a BMW524TD, intercooled and boost set at 14lbs for the last 140000km or so. No idea what HP it makes, suffice to say it's Quick   . Driven hard most of the time. Oil has been PC duron synthetic since I bought it with 80000km on it. I replaced the bearings and the bolts and buttoned it back up.

It would appear that rod bearings may be sort of a maintenance item if you drive your modded diesel hard. I have the kolbenschmidt catalog and they show a "sputter" type bearing shell for the TDI 115hp and up. Sputtered bearings tend to have much better fatigue resistance. These might be a good upgrade if you were rebuilding an engine. They would be a drop in for a 1.9TD/TDI.

As a side note the pedal vibration remains the same. The noise/vibration cease when the clutch is fully engaged or disengaged. It gets worse the more fuel you give it and almost completely disappears as the "throttle" is lifted. It's quite audible, emitting a load "graunch" everytime the clutch pedal play is taken up. Seems like a "half order" vibration, about half as fast as crank speed. Anybody have any insight on this? In chasing this pedal vibration I've replaced the release bearing, the engine and tranny mounts, the rod bearings and checked the crank endplay (0.005"). Nothing has helped... I'm starting to wonder if something is amiss in the clutch itself but it works fine otherwise. No slipping or anything. It seems odd that it only occurs under power. If something were warped it wouldn't "unwarp" when the throttle is lifted...

[fatmobile]

. I replaced the bearings and the bolts

 Are you supposed to change the rod bolts with the bearings?

[QuickTD]

On the 1.9TD and TDI the rod bolts are "stretch" bolts and must be replaced. I'm not sure about the 1.6D/TD.

[DieselsRcool]

Have you checked the crankshaft end play?

[QuickTD]

Yes, I mentioned that in my previous post. It's 0.005" which is the tight end of the spec.

I think I finally got the image to work...

[DieselsRcool]

Mmmm....
Could it be a broken flex plate flexing under load? Looks like the next step is to drop the tranny. I had similar noises and thought it was the clutch. I dropped the tranny and after removing the clutch discovered .090" end play. :shock: The thrust bearing sides of the center main had completely failed. When I removed the rod caps you could see how the crank had been pushed to the side causing the rod bearings to wear a crescent shape of copper color in all four. I certainly don't see this in yours.

Keep us informed, I'm curious now.
Larry

[QuickTD]

Could it be a broken flex plate flexing under load?

Thats sort of the direction I'm headed. I hear about a lot of pressure plates failing due to the sheet metal drive straps breaking. I'm wondering if this could be it? If one strap were broken the pressure plate would be forced off centre under load.

I've already checked the flywheel/pressure plate bolts for tightness through the starter hole. Any loose parts or bolts would have fallen out completely by now though, the car's been doing this for 50000km at least. gotten progressively worse though.

Funny you mention the thrust bearings. I just worked on a 90 golf 1.6TD (450000km on the clock) that had similar problems. I repaired a leak at the injection pump throttle shaft and noticed the crank walking around as the engine idled. I shut it off and pulled the crank in and out, it must have had 1/8" of end play! The owner didn't wan't to fix it and sold the car the next day. Odd thing was the clutch pedal was perfectly smooth, in fact the whole engine ran alot smoother than mine at high revs...

[dub]

I just changed my rod bearings too (and oil pump). I replaced the bearing with ones that had a hole in the middle of it. Are these cool to use?

I forgot to check the play in the crankshaft, but I didn't notice it budging when I gave it a wiggle.

I have an 85 jetta 1.6 N/A.

p.s. I need to replace my vacuum pump too. anybody have one?

[fspGTD]

Are you looking for the newer slender radial style vacuum pump, not the older diaphgarm style?  If so, I've got an extra one of those that I've only recently removed from my car and it works great - IM or e-mail me.

[dub]

so has anyone else replaced their rod bearings with new ones that have a hole in the middle of them? (unlike the ones pictured in the above post

[81rabbit]

I just got rod bearings and they have the holes as well. I had the guy double check them and he said they were the right kind I guess I'll find out. :?

-J

[QuickTD]

OK heres the skinny, I looked up rod bearings in the kolbenschmidt catalog. The bearings with holes in them are officially for gas engines. They are the same size, type and alloy as diesel parts. The only difference is the holes. I'm not sure what they feed on the gasser, but they will be blocked in a diesel. I wouldn't loose sleep over it. Many jobbers just stock one set of bearings for all 4cyl VW's since they will all interchange. Main bearings are generally done the same way. The jobber stocks the set with an extra grooved shell. A diesel normally has all solid shells on the bottom. On the gassers the "extra" grooved shell goes on the bottom of the #4 main to improve oil supply to the #4 rod. This is done because the oil passage for the cylinder tends to steal a bit of pressure from the #4 main.

[rabbit_tdi]

If the hole is in the top bearing shell of the connecting rod, I would not use it in my diesel.  The cylinder pressure is higher in a diesel, and consequently the rod bearing loads are higher.  A hole in the top bearing shell reduces the surface area of the bearing which is used to sustain the load on the connecting rod.  :-)

As to why the hole exists: some connecting rods are drilled from the big-end all the way to the piston pin, and is intended to transport oil to the piston pin.

[rabbit_tdi]

The noises and vibration associated with the clutch, sound most peculiar.  The closest thing that I can think of, reminds me of a Jeep which had the springs and hub fail in the clutch disc.  It was many years ago, however I remember it as making odd noises and vibrating.  Perhaps?  :-)

[QuickTD]

I'm posting a follow up in light of the recent interest in this thread. I did end up replacing the clutch, pressure plate release bearing and clutch pushrod seal and bushing. The clutch was worn but not really damaged in any way. I replaced the clutch cable with a manual adjusting version, this actually did help the pedal feel, the self adjusting mechanism would slip a bit under engine vibration before taking a firm hold and the plastic cable liner was worn through giving it a bit of "crunchy" action.  Never did find a real cause for the pedal vibration and it persists to some degree. For lack of a better explanation, I have decided to attribute it to crank flex under load. The increase in pedal vibration seemed to worsen in direct proportion to the increases in engine power that I was achieving at the time. It has not worsened in the past couple of years and the car is now approaching 315000km, still running strong.