Diesel Rebuild

[jimjamjo]

Hi

 

I've just rebuilt my 1.9 tdi with honed bores, new std pistons and recon head.

 

Took it down the road and it's smooth but a bit oil smokey. Will that go away as it beds in?

 

Cheers

 

Paul

[chromedome]

I'm not sure if this is still relevant for modern engines.

 

In the past you had to take the shine off the bores by lightly rubbing them with wire wool. This enables the oil rings to bed in and stops the oil smoke.

 

A friend of mine rebuilt his Jag engine and didn't take the shine off the bores. After a few hundred miles it still smoked so he had to strip it down again. :(

[GSMGuy]

Don't skimp on the throttle, and work it a little bit to prevent the bores being polished, as this will also increase oil use..

 

Mike

[johnb80]

The fact that the bores have been honed will mean that the glaze has been removed so forget the wirewool (you wern't going to take it apart again anyway were you). It will take time for the rings and the bores to bed in together, do not give it too much right foot to start with, freely revving and lightly loaded. The machining that has taken place will not be of the same standard as when new so go carefully. When you do start to use the throttle do it for very brief periods and gradually build it up. You should expect the oil useage to decrease as the miles build up.

 

Regards - John

[Masked Marauder]

If it is not a PD, then don't use semi-sythetic or synthetic oil for running in a rebuilt engine. Do the first 500 miles on a mineral oil.

[jimjamjo]

Thanks

 

It's getting a lot better now after about 40 miles. I'm using semi synth though - bummer it cost

[Guest marcusheawood]

...that'll be the problem then, synthetic bases are a little too thin which is why they're not useful for new engines.

[jimjamjo]

Isn't the thickness down to the grade e.g. 10W40?

 

The smokes gone althogether now after 100miles - apart from a bit on a cold start. What s the best to use once I've run it it?

[Masked Marauder]

Quantum semi-synthetic.

[jimjamjo]

Thanks

 

I'll go for the Quantum as its VW and cheap.

 

I've done about 250 miles so far and get a cloud of oil smoke on the first start of the morning.

 

After a couple of seconds, it's fine. That makes me think the valve seals are suspect which is unlikely as they were changed when I got the head reconned?

[Guest marcusheawood]

I doubt it, more likely that the bores are still bedding in....it is possible that you've glazed it slightly with all that early smokin', still should be good to boot it now.

 

The best way to bust the glaze and bed the rings/bores in is to thrash it hard through the gears (downshifts too), and DON'T do motorway type miles, take the scenic routes everywhere until it's settled down.

[jimjamjo]

It only smokes first thing in the morning - there's a puff when you first start it which makes me think that oils draining down rather than creeping up the sides of the bore overnight?

[Masked Marauder]

Did you re-condition the head or was it someone else?

 

The valve stem tops where the cotters fit in are very sharp on VW engines, and if you don't use a guide it is very easy to tear the soft faces on the stem seals when you push them over the valve.

[jimjamjo]

Hi MM

 

 

I took the head to a workshop - I'd trust the guy though - very competent.

 

Going back to the bores - when I took the old pistons out there was still some crosshatching from new. I gave each cylinder about 40 secs with a honer on the std medium stone (after removing the piston cooling jets) using plenty of brake fluid as lubricant. I ended up with a pretty coarse finish although it was hard to get a crosshatch more than 40 degrees as I didn't have a slow drill. So I think the smoke on the first 100 miles was due to oil planing up the coarse crosshatching.

[jimjamjo]

I've looked at the title of this post and thought I've give some background on the rebuild and the car - it had done 120k as a taxi when I got it. The engine was always clean and quiet when running... apart from pinking under load. I changed the oil and filter every 10k and did 40k in 3 years.

 

This summer we took it up to the Lakes and over the infamous Hard-Knott pass. It overheated on the pass with the needle touching the red. I've got an old TR6 so didn't think the needle touching the red was a big deal :blink:

 

Anyway, a couple of weeks later, I noticed it running rough at the end of a long journey. Next day, I started it up, oil smoke everywhere, smoke out of the dip stick and missing a cylinder. Chap from the AA said that it would get worse if we tried driving it home so... we drove it home 100miles. Surprisingly, it got much better on the motorway.

 

Took it apart and found a lot of carbon, the piston crowns all had hairline cracks - the worst on cylinder 3 which you could put a fingernail in. The bores looked ok but on 3 it looked like there was a blow by on the top ring. 3 piston looked like the top ring was pinched in at one side with no play.

 

Also, I'd never checked the coolant - looked like drinking water when I drained the system.

 

Got some new German std pistons for

[Guest marcusheawood]

Jesus! Thats a bit excessive with the hone, coarse is only for busting the glaze, once you're through it you need a fairly fine stone to finish. 45 degree crosshatch at a slow speed, should only take a few seconds per bore.

 

I think it'll take you ages to run this one in.

[jimjamjo]

Depends if you are glaze breaking or trying to remove a lip. I checked several sites which recommended at least 30 seconds on each bore, at least 14 strokes