308 timing belt drive bearings - FIXED !

PROCEDURE -
Same as for changing the belts, I got to the stage where the AC compressor has to come off. This looked impossible because you can only get to the lower bracket. It was tempting to start removing the fuel tank, but if Verell Boaen says it’s only necessary to lever out the upper rubbers on the upper bracket then that was fine by me and it worked. The tin can thing on top of the fuel tank with 4 pipes coming out of it also had to be removed so that the compressor could hang over the tank out of the way.

To get the damper off the crank, the bolt came off easily with an air wrench but the damper itself needed a hefty pulley extractor (borrowed from work). After removing the belt covers, you arrive at the drive pulleys. In my case both shafts showed no play and as the design had the seal on the outside I thought it better to try and replace all the bearings. Others have written that the wear can be so bad that the ball bearings practically fall out into your lap. Those engines must sound just great.

After draining the oil, the sump has to come off which is OK but you have to remove the oil temperature sensor and the dipstick tube and the bit of tubing that goes down into the sump, (what’s that for then?) first.

Peering up into the sump was when my stomach really turned over. I could hardly see the three bolts holding the oil pick up tube, let alone see how to get them off. It really doesn’t look possible. Basically I went off to cut some trees down in the garden and then got around to ordering the tools that, according to Verell and Robert, would do the trick.

Most important is a ¼ inch 10 mm flexi-drive socket. If you can get a short reach 12 point one then all the better. Makes little difference though because in any case you have to grind it down to a mere wisp. Everything off it’s length until it will just catch a nut, and everything off it’s diameter until it’s about to fall to bits. It’s important also to minimise it’s profile in it’s articulated position (so take off any edges sticking out). Anyway this together with extension pieces to the ratchet, and various normal 10 mm spanners, some ground down, and a great deal of patience, got the nuts off.

 

The pick up tube should just slip off. Mine didn’t. It slid down the studs and collided with the rear wall on the right hand side. However, since the alternative was to take the engine out, I gave it a hefty pull and off it came.

Next step was to double-nut the studs off. It was fiddly to get the nuts on and long thin fingers were a definite asset. It was also difficult to get access for two spanners to lock the nuts against each other. Although once done, the studs weren’t in particularly hard. The right hand stud had so little clearance to the sloping back wall that I had to grind the two nuts to about half their thickness and keep them right up to the top off the stud.

 

Returning to the outside of the engine and what now seemed a relatively spacious wheel arch I set about removing the belts. The camshafts had been marked by somebody else at the TDC position and I marked the pulleys with a horizontal line. Also made common location marks on the belts and pulleys and the camshafts as an extra precaution.

Next all the vertical studs on the outside were double-nutted off. I tried a borrowed stud extractor but this needed more space and more length of stud than was showing. When the nuts on the horizontal studs were off, the timing cover should have slipped off. Mine was close to the water pump but it was possible to use a hack-saw blade to ensure a gap. The oil pump however was sticking down on the inside of the timing cover so that the sump casting had to be levered down out of the way to allow the timing cover to come off. As the cover comes off the pulleys rotate slightly anti-clockwise because of the helical gears

 

The tool to get the slotted crown nuts off was relatively expensive (£130 Ferrari and ~£90 elsewhere) and as we had a M17x1 thread tap at work I was quite keen to make some normal hexagon nuts. It is possible to grind up a tool from a socket but the nuts have to be tightened afterwards with a high torque and I wasn’t confident about doing this with a home fettled tool.

The crown nuts were removed by drilling a hole in their flank. First 2mm diameter, then 3 and 4, a gentle tap and they crack open. By positioning the hole by one of the self-locking slots, that part of the cross section was already free

 

The shafts could now be knocked out with a soft mallet holding the timing cover in the hand. Then after removing the circlips and spring spacers, the bearings could also be driven out with the right sized socket for the outer race.

Removing the inner bearings from the crankcase was a bit more tricky.
I had to grind a bolt shaft to hammer behind the bearings to get them to move a little so that an extractor could get behind them.

 

Then I ground up an extractor from a bolt, although it took some time to get it to fit. There’s probably such things available to be bought. I don’t know. The tips were hardened by heat treating which sounds good huh. Basically it’s just heating it up till the yellow colour gets to the tip and then dunking it in water. (Learnt that in apprentice training along with filing flat surfaces - impossible - and welding up air tight boxes - entertaining-). The bearings then needed a few hefty taps with a slide hammer.

 

Now the re-assembly. Here I was really paranoid about cleanliness. Firstly whatever goes into the sump could be sucked up into the oil pump and secondly I just did not want to be doing this job again anytime soon.

The bearings go in fairly easily using various bits of wood, pipes and sockets to hit the inner or outer races as necessary. I used a trace of silicon rubber on the outside of the three oil seals. The crank oil seal was difficult to get in square although the toothed drive pulley turned out to be the right size to get it in. I primed all the bearings with a smear of graphite grease and oil, just to get them started.

The offending bit of the oil pump cover was filed off.

 

The threaded holes for the pick-up studs were cleaned and greased so that the studs were going to go in really easily. I mean REALLY easily.

 

To get the timing cover back onto the block was a bit tricky. There’s an O-ring on one stud that goes into the pump suction side. Luckily a Biro pen just fitted in the hole to keep the O-ring in place

 

The manual says to fit the timing cover gasket without sealant but I hadn’t been able to clean the crankcase surface properly so I put high-temperature sealant on that side only, taking care to keep it away from the oil passage. I then applied more sealant to the horizontal surface. This is where it gets tricky. The timing cover has to go on with the drive gears lined up properly (that is slightly anti-clockwise to how they came off) and the crank oil seal must not get pinched (needs a smooth small screwdriver to run round the edge) and all before the sealant goes off. I needed 3 or 4 goes to get it right, including cleaning off all the sealant and starting again once. It’s also a good idea to oil the contact surface where the pick-up tube goes so that although it gets covered in sealant on the way in, it won’t stick. It’s hard to clean afterwards.

I ground off material from the oil pick-up pipe where it had interfered with the rear wall, (although I took off even more after this picture)

 

Once more under the sump, I cleaned around the ledge under the timing cover since this was now full of bits of old gasket, sealant and aluminium filings. Getting the three pick-up tube studs back in was certainly tricky, but with patience, long fingers and having cleaned and greased the threads, it worked. As Verell suggests, a smear of sealant on the top of the gasket keeps it in place, and super-glueing the washers to the pick up flange means you don’t have to get a washer and a nut on the stud which would be impossible. Getting the nuts started on the studs is tricky again but once they’re on and tightened that’s it. All downhill from there on and the world looks a better place.

Re-assembly is straight forward. The 17x1 hexagon nuts worked a treat and made it really easy to put on the high recommended torque.

 

Fitting the new belts and tensioners (£65 complete from Superperformance UK) was also straight forward. Not having done the belts before I was pleased to have both the belts marked up and also the cam pulleys marked up. This gives a good degree of confidence that you haven’t cocked anything up with the timing.

The engine has to be virtually re-built before you can run the engine to check whether it has been successful. The only thing you can leave off is the left hand belt cover. The AC compressor, alternator, water works, all have to go on.

Right that’s it………….hope the pictures were interesting anyway

I'm just waiting for the bang at 7500 rpm

Richard

 

The M17x1 nuts cost me a bottle of wine, but the friend that did them reckons about 30 mins on a lathe for the 2. He said he used a fine thread M16 nut (M16x1.5), faced off to final nut height, bored out and chamfered to 17 dia., then run through with the M17 x 1 tap. It’s important to do the operations in one go so the thread and final face are square. I used a good quality M17 washer as well.

There are no worries about the strength as the normal torque for the 10.9 M16x1.5 is around 33 kgm so the 12 kgm required is fine.

I could imagine doing a small batch in a CNC workshop, wouldn’t cost much.

 

Don't be put off. I basically enjoyed it. The only thing that could maybe scupper the job is those 3 b***y studs on the pick-up tube.

How long are your fingers ??

 

About 4 weekends and some evenings but I'm a comparative virgin F-car fiddler.

 

The company where we both work just 'had it' in the tool stores, but it is a non standard thread.

I see you have machining as a hobby, if you were just doing two of them, could you cut the thread on a lathe with a pointed tool or whatever they are called?

If you want I can pick off the important dimensions from the the tap and find the basic dimensions of the thread.

Richard