Actually had a few consecutive hours available today so flipped a coin between pulling the alternator on the Jag (which has of course started working again) and delving into the diagnosis of what's going on with the Merc.
Merc won.
Step 1 I decided was to have a proper look at the camshaft. I knew a couple of lobes were badly scored but wanted to see what state the bearings were in - I had a feeling they were likely to be shot and haemorrhaging oil, hence the less than stellar pressure at a hot idle.
Off we go again. Getting used to doing this now!
Let's have a peek at what lies under each of the rocker assemblies one at a time.
So what's behind door number 1...
Pretty much exactly what I was expecting to be honest.
An impressively scored up bearing with a lot of slack, which you can actually see looking closer. Pretty sure you shouldn't be able to slot a finger nail between the camshaft and the carrier.
Don't think I need to get a Plastigauge out to confirm there's too much free play there.
The cam followers feature some pretty epic scoring as well...the deepest of which must be about half a millimetre deep.
Number 2 was pretty similar, though with slightly more severe bearing scoring, cam followers were *slightly* less mangled.
This was the first one where I couldn't remove all of the bolts from the rocker frame itself because of how much carbon buildup there is in the bolt holes!
Number 3 however was where things got real exciting...
The cam followers are utterly wrecked, both inlet and exhaust.
That however pales into total insignificance compared to the state of the camshaft...
Wait...that doesn't look right, let me move a bit to get a better look...wait...what the? Oh hell...
Yep... pretty much the entire cam lobe of the number 3 inlet valve has been totally *obliterated.*
I'm pretty certain this is the most mangled non-broken camshaft I have ever seen... it's *definitely* the worst I've ever seen on a running engine. Never mind one that seemed to be running quite happily aside from being a bit rattly. That's easily 5mm plus change of material that has been worn away.
Number 4 also has quite a lip on the exhaust valve...which would have been impressive wear if we hadn't just seen the above photos.
Number 4 inlet actually looks normal!
The followers on this one were probably the least badly deformed of the lot, though that's not saying much.
Goes without saying that the whole camshaft assembly inboard of the timing sprocket is scrap metal. Well I don't think it is actually...this is more the sort of artefact that should be hung on the garage wall as a warning to future generations!
I did start the engine up with the rocker cover off briefly simply because I wanted to confirm we did have good oil flow up there, as there's obviously a load of damage been caused by oil starvation or *severe* contamination. We do - in fact so much oil is gushing out from around the rear two and front bearing that it totally overwhems the drains in the respective areas of the head and starts flooding over the top of the head after the engine has been running for about five seconds.
Probably why everything under the car looks like this and why so much was pouring out before the rocker cover seal was changed.
Definitely plenty of oil getting to the camshaft now...
Though sadly too late, this hardware was mortally wounded years if not decades ago.
There's like 1/8" of this gritty sludge just caked over everything.
If you remember back to when I first set the valve clearances I checked and found that the spray bar which runs above the camshaft was about 70% clogged, with the front most jet being the only one that was working properly. This ties in with where the most damage seems to be...so I'm calling on oil starvation as the main cause. The lack of zinc additives in modern oils probably hasn't helped given the cam follower design. A separate additive will definitely be going in with the oil once this mess is sorted out.
It's a bit hard to see, but in person you can make out glittery residue in the head valley around number 3 far more than anywhere else, which supports the thought that the mangled camshaft may be where a lot of the glitter I found in the oil had come from.
So if the bottom end has survived, we might just get away with a head swap.
Before going all the way down that lengthy road (being used to OHV engines a head swap on an OHC engine feels daunting!) I'd really like to take a look at the condition of the engine bottom end. Simple enough to get a quick health assessment done, drop sump, pop a couple of bearing caps off and see if we can see copper and if the crankshaft looks smoother than the surface of the moon. Simple enough.
Oh.
How the bleep do you get the sump off this thing? There's a stinking great cross member in the way. Sump appears to go back to about the red marker in this photo, a good foot or so behind the front of the aforementioned metalwork.
Even if I could figure out how to get to the half dozen or so bolts buried above it and removed the engine mount attached to it... I'm not convinced I'd have enough clearance to pull it out.
Think I need to go do some reading to figure out what really simple trick it is that I've missed...or getting the sump out will wind up with me 3/4 of the way down the road to removing the engine...by which point I may as well just take it out anyway! Feels like I must be missing something though given how serviceable most things on this car seem to be. I did wonder if the sump was split into a front and rear half, but if so I can't see the join.
Definitely an instructive day...and kinds good news in a way. The camshaft being so chewed up to this extent definitely would have an impact on oil pressure I'd think and we've definitely found a likely cause for the glitter. It's just possible the bottom end might have survived...
Either way I want to check the condition of it before going to the trouble and expense of a head swap. Plus given the amount of grime in and around the top end I fully expect the sump to be as bad or worse...and worry about the oil pickup strainer.
Now I just need to figure out how the fluff to get the sump off! Simple right?
