Engine Oil Loss - Bad News
Monday, June 30th, 2008
I have pursued the oil loss issue harshly. Some external leaks were evident already, mainly accumulating on the bottom left side of the flywheel housing. It now seems that this was due to a split rocker cover seal, which is being replaced. That’s the easy bit.
I also found approximately one pint (1/2 litre) of engine oil in the air filter. This has been deposited by the crank case breather, which on my installation connects to the intake tract between the snorkel and air filter (normally it connects between the filter and turbo on Tdis). The level built up over the 2,500 miles that the vehicle has done since the engine was fitted, and could not drain out because I had left the wading bung in the bottom of my custom filter drain, not having expected any such problems.
I checked the breather hose and the hose from the cyclonic filter (the black plastic pot on the right side of the head) to the sump, and both were clear. The amount of breathing was low - about 1/3-1/2 that of the 300Tdi in my Range Rover, which doesn’t loose a drop of oil. I have fitted a new cyclonic filter, as the old one clearly wasn’t separating the oil vapour from the venting gasses. However, always suspicious, I decided to remove the cylinder head to check for any abnormalities. I was horrified to discover heavy coking (carbon deposits) around the edges of the pistons and scrubbing/polishing marks on the bores (looking a bit like scoring) from the carbon on the sides of the piston crowns. On removing and cleaning the pistons, I found the oil control rings on pistons 2 and 3 to be cracked, but this looks like it may have occurred as the pistons were removed (the delicate rings binding on the coke lip at the top of the bores), as there is no actual bore scoring.
I am now waiting for delivery of new rings, which Turner Engineering are rushing to me. Turners have been extremely helpful, with plenty of advice and diagnosis. The strong belief is that this coking and subsequent oil loss is a result of running on SVO (vegoil), despite the heat exchanger and relatively low mileage that it has done on the fuel (it has only used about 25 gallons/100 litres of it). There is some slim hope that it may be down to me switching back to diesel too late on each run to fully purge the vegoil from the injection system before the next start - I have been using a distance of three to four miles, but this may need to be drastically increased.
The rings should arrive tomorrow, at which point I can start to reassemble the engine - I have all the other parts required. The trouble is that I’m back at work for the next five days, and then next days off are meant to be a short, four day “shake-down” trip with the family to get used to the tent, the camping equipment and stowing all the kit in the 109 before the Alps trip in three weeks. I’m praying that I don’t get called in on the two stand-by days in this week’s work!
As a small note, here’s another problem I had with this work. Those who read about the alterations I made to mate the flywheel housing to the gearbox bell housing will remember that I used four countersunk bolts to secure the flywheel housing to the ladder frame below the block, and fitted new studs to the blind holes to use the bell housing’s existing stud pattern. This arrangement is the neatest and strongest way to mate the Tdi to a Series box, but has the problem of covering the countersunk bolts once the box and engine are connected. The units have to be separated to remove the ladder to gain access to the crank shaft and big ends.
I didn’t fancy removing the gearbox again (a day’s work), so I came up with a quicker and more viable long term solution: I drilled the bell housing in line with the countersunk bolts to expose their heads - they can now be removed through the bell housing without separating the bell housing from the flywhell housing. The holes were drilled just large enough for the socket-head bolts (round headed, Allen key type) to pass through, and leave the clutch area water tight. This means that I still have the full strength of the complete bolt set from flywheel case to engine, and the full bell housing stud pattern. If anyone is going to fit a Tdi, I strongly urge them to do this mod to the bell housing while the flywheel housing is off the engine - it’d be much easier and quicker with the flywheel housing as a template and working from inside the engine bay that from between the cross members under the gearbox!
The main lesson from this post, though, is to be very wary of using vegoil as fuel. I will be investigating ways of preventing more coking before I use vegoil again.
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