My SLK55 had been annoying me with a persistent oil drip from the rear main crankshaft seal for a little while, but I also had in the back of my mind that O ring business on the oil pump pickup tube. This is a naturally aspirated M113, 5.4 litre unit. V8, natch 
There were no particular symptoms, but the car has seen a few trackdays and whilst it’s never been thrashed, it has been used as the manufacturer intended for many of it’s 105,000 miles. The engine mounts needed replacement too…. Oh, why not?
I flicked the engine out on Saturday morning, put it on a stand and was round Nana’s for lunch at midday.
Had a spare moment today, so picked it open. The rear main was actually leaking from the plate, so probably glad we were having the sump off, as it’s easier to get it back on the dowels and also gives a chance to check on the oil drain U bend. It was fine incidentally…
Upper conrod bearing shells weren’t though…
They were almost down to the copper! Not gone right through, but the white metal is so thin you can see the copper through it. All the upper shells were the same.
The lower shells were hardly worn, but you’d expect that.
I think this certainly didn’t help. The O ring on the oil pickup tube was pretty hard. Not absolutely rock hard, but harder than I’d like. More importantly the tube just fell out of the pump when I unbolted the brackets. The O ring wasn’t gripping it at all.
Something else I found was on the anti-drain valve that fits into the block just above the oil pump outlet. The seal on it was turned over on the edge. It had been like that from the day it was assembled. The rubber protrudes a bit from the face of the block to seal against the pump when it’s bolted down. The builder must have shoogled the pump a bit to line up the holes, caught the edge of the seal and turned it over. I’ve got a new one coming Wednesday.
I don’t know if the O ring is definitely responsible for the bearing wear, but I’m sure glad I found it and have sorted it out. As I say, the car hasn’t had a super hard life. Anyone who knows these engines will tell you they all rub the oil pump chain on the little casting on the timing cover that stops the camchain falling off the crank sprocket when the cams are out. I’ve seen them worn nearly halfway through on baggy engines. This only has the slightest nick on that area.
I’ve probably put this in the wrong section, sorry.
There were no particular symptoms, but the car has seen a few trackdays and whilst it’s never been thrashed, it has been used as the manufacturer intended for many of it’s 105,000 miles. The engine mounts needed replacement too…. Oh, why not?
I flicked the engine out on Saturday morning, put it on a stand and was round Nana’s for lunch at midday.
Had a spare moment today, so picked it open. The rear main was actually leaking from the plate, so probably glad we were having the sump off, as it’s easier to get it back on the dowels and also gives a chance to check on the oil drain U bend. It was fine incidentally…
Upper conrod bearing shells weren’t though…
They were almost down to the copper! Not gone right through, but the white metal is so thin you can see the copper through it. All the upper shells were the same.
The lower shells were hardly worn, but you’d expect that.
I think this certainly didn’t help. The O ring on the oil pickup tube was pretty hard. Not absolutely rock hard, but harder than I’d like. More importantly the tube just fell out of the pump when I unbolted the brackets. The O ring wasn’t gripping it at all.
Something else I found was on the anti-drain valve that fits into the block just above the oil pump outlet. The seal on it was turned over on the edge. It had been like that from the day it was assembled. The rubber protrudes a bit from the face of the block to seal against the pump when it’s bolted down. The builder must have shoogled the pump a bit to line up the holes, caught the edge of the seal and turned it over. I’ve got a new one coming Wednesday.
I don’t know if the O ring is definitely responsible for the bearing wear, but I’m sure glad I found it and have sorted it out. As I say, the car hasn’t had a super hard life. Anyone who knows these engines will tell you they all rub the oil pump chain on the little casting on the timing cover that stops the camchain falling off the crank sprocket when the cams are out. I’ve seen them worn nearly halfway through on baggy engines. This only has the slightest nick on that area.
I’ve probably put this in the wrong section, sorry.
