Thursday, 6 November 2008

Engine Overhaul

Repairing Daniel's Vauxhall Astra

A 1993 with C14SE engine

2nd to 4th June 2008

Rough running, very noisy valve gear. Low compression on No 2. Emulsified oil in valve cover.

Top end overhaul and inspection of valve gear.

First day,
strip down.
Removed O/S inner sill cover, 3 torx screws, revealed fuel pump relay inside 'A' pillar base and removed it. Turned engine over, fired then stopped. Fuel system now de-pressurized. Disconnected battery.
Removed air filter housing. Removed auxillary belt and tucked it out the way. (captive by engine mounting). Removed timing belt top cover (3 x 10mm bolts). Jacked up front O/S and removed wheel to gain access to lower side of engine. Removed wheel well access cover, (2 x self tapping bolts and plastic rivet). Turned engine to No1 TDC, to align timing marks, (previously high lit with white paint, suggesting previous work)
Attempted to remove crank pulley bolt by putting in gear and with wheel on the road, no go.
Had to weld adjustment to my previously made chain wrench, wrap the crank pulley with cycle inner tube and used that successfully to remove bolt. (18mm ring spanner)
Removed lower belt cover, 3 x 10mm bolts.
Inspection of timing belt, OK. The adjuster indicator, showed that it was slack. Removed timing belt, holding the adjuster back with a drill in the locating hole. Tried to undo the back timing belt cover. (4 x Torx30 head screws) 1 very tight and broke one of my torx set, left it. Tried to loosen the water pump securing screws (3 x 5mm allen). 1 very tight and tool in risk of chewing it, left it.
Drained coolant by siphon from expansion chamber.
Removed throttle cable, injector electrics and various pipes and hoses from the inlet manifold.
Removed Cam sprocket. Had to make up a tool to hold the cam sprocket still.
Tried to remove exhaust down pipe from the manifold. One bolt and spring came off OK but the other had a chewed head and couldn't get a spanner to fit. Ended up angle grinding the head off.
Removed the cylinder head bolts in reverse tightening sequence. (standard hex head bolts).
Lifted the cam carrier off, pushing the plastic belt cover aside to clear the sprocket end.
Removed the rockers, slippers and hydraulic tappets, keeping them in order in a sectioned box.
The damage to No 2 cylinder valve gear was immediately apparent. The cam lobes were horribly re-profiled and the rockers worn badly. Most of the other cam lobes were OK but showed deep scratches and wear. (See picture at the top)

Removed the cylinder head complete with manifolds.
Dismantled manifolds from head on the bench. Most of the exhaust studs came out with the nuts.
Tried to remove the bolt remains from the exhaust manifold. It was only moving a bit but showed signs of cross threading. Used a stilson wrench and broke it off leaving the remains in the hole. Gave up for the day.

Second day,

Clean up and rebuild.

Sourced a secondhand cam complete with housing, rockers and slippers, just at the end of the road at Sadds yard.
Cleaned all the old gasket from the cylinder head and engine block. Looked in very good condition, very little carbon deposits.
Siphoned more coolant from the block. Took the Exhaust manifold to Towler engineering, Oxford road, for them to drill out and tap the hole. Collected the new cylinder head bolts from CMD and Exhaust studs, bolts, springs and sealant from Vauxhall main agents.
When I went to collect the manifold from the engineers they pointed out that it was also cracked and offered to weld it up. I did consider scrapping it and getting another from the breakers, But decided that as they had already done a good job on the bolt hole to continue with it.
Inspected the old tappets and stripped the ones down from No2. One wouldn't come apart, so tried one of the others. The stuck one eventually came apart and I compared it with the good one. Showed signs of wear scratches on the piston. I decided that this was the probable cause of failure, wearing the cam lobe when the adjuster failed. Went to the breakers again and picked up 2 tappets to replace the suspect ones.
Removed the valves from No2 and lapped them in after inspection. The valves were in near perfect condition and needed very little lapping using fine paste. After doing the valves for No3 decided that I was probably doing more harm than good, as they were in such good condition and previous compression tests proved the other cylinders were fine.
Re-assembled the head with new gasket on the block. Tried a dry test fit with the new bolts and found that the bolt heads were different. I needed a star socket tool to fit them. CMD didn't have one but determined that it was an E12 socket. Sourced one at Halfords.
Picked up the manifold from Towlers. They had skimmed the mating surface as well, nice job.
Assembled the tappets, slippers and rockers on top of the valves. Found that one of the rockers supplied with the camshaft was odd. Same dimensions but a lighter construction. The new rockers were the same as the old, but had a hole drilled in each over the tappet socket. I chose the best of the old ones and put it in the No1 position. Its now the only one without an oil hole.
Applied green jointing compound to the top of the cylinder head and lowered the cam unit on top after checking the timing marks. Torqued down the head in sequence and the four stages, as per the book. An initial torque setting and then three 60ยบ angle turns in sequence, done by eye.
Assembled the inlet manifold on the head and found that it is very awkward to get the nuts on the lower side. Various pipes and a cooling water gantry get in the way and its impossible to see. It would have been better, with hindsight, to attach it to the head before mounting.
Gave up for the evening.

Third day,
Final assembly and start

Struggled with the inlet manifold and finally got it fastened. Re-attached all the various vacuum pipes and electrics to the manifold and plugged in the injectors. Hard to find home for two of the vacuum pipes. One went to a circuit board on the bulkhead and the other under the air mass meter.
Went to attach the exhaust manifold, after inserting new studs, where they were missing and found that it was distorted and didn't line up with the studs. The welding must have closed up the crack and pulled the sides in. Again, I wished that I had scrapped it.
Decided to re-drill the holes to elongate them using the gasket as a template. Re-fitted the manifold with new copper nuts and anti-seize compound.
Re-attached the down pipe with the new bolts and springs, using anti-seize on the bolts and fire paste in the pipe socket.
Inserted the spark plugs and wiring.
Using a new torx30 socket I managed to release the final screw holding the cam belt rear cover and gain access to the water pump. I managed to release the final hex socket bolt on the pump, so they were all loose. I didn't really want to release the water pump to adjust the cam belt unless absolutely necessary, as it was sealing OK and looks recently replaced. Re-fitted the bolts with anti-seize paste. I tried a dry fit of the cam belt as see if it was at the right tension. The marker on the idler showed that it was. Put the crank pulley back on using my chain wrench. Then discovered that I couldn't get the back cover on, so had to take it back off again. Re-attached the rear cover and then re-assembled the cam belt, holding the tensioner back using a drill in the holes in the pointer. The crank pulley was tightened using an 18mm ring spanner as tight as I could. The cam sprocket was tightened to the required torque using the tool I previously made to hold the sprocket still. Turned the engine over twice using the spanner on the crank bolt and re-checked the tension. Perfect.
Re-assembled the final parts, alternator, air cleaner and crank speed sensor wiring. Re-filled the water and a final check everything OK. Replaced the fuel pump relay and put the covers back. Re-connected the battery negative terminal. Fingers crossed.
Turned the starter. After about 2 revolutions the engine fired and then stopped. Second turn it ran for a couple of seconds. Third attempt it ran and ticked over. A slight rattle from the top until the adjusters pumped up and then sweet.
Job done.
Road test.
All OK, but the engine management warning light comes on for a few minutes and then off.

1 comment:

Jan said...

Great idea ,(Maurice is not working tomorrow ) do you think I should practise on his car ??? Jan xx