30 Nov 2023

So I've been MIA on this topic for a couple of months. There's some valid reasons for that. We have been whittling down our rather excessive fleet of cars here, and that included a CF 6spd Coupe, an SRT6 coupe, my very last SRT4 (which I have owned since 2006), and a PTGT parts car. I am also in the process of prepping our 1962 Triumph TR3b to be sold. We're down to a much more reasonable fleet around here, and I am proud to say that everything here can run and drive on its own at the moment! This was not the case just a few weeks ago. A couple of weeks after the fall rally, testing of the 7G setup on the CF resumed. Progress was really moving along, and the car was really starting to come into its own. One day, a CEL came up with a code for a misfire on #7. It had been running fine. Clearing the code made the car run well, until it would come back. A slight miss at idle was noticed, but after that it was OK, until the light would come back. A few days of clearing the code, driving, light coming on, and clearing again ensued. The ME2.8(.1) in these cars will shut down a misfiring cylinder after x number of misses. Coil was changed, which is the typical failure for this code. Same results. Tried the wires, same thing. Pulled the plugs, they looked fine and clean, changed them, code came back. Checked fuel injector, and it was OK. uh oh. Break out the compression gauge, and check surrounding cylinders for reference. #5 and #6 yielded 170psi. #7 yielded 70psi. oh boy.

Three main possibilities. One, the head gasket is blown. Two, valve is burned. Three, piston is cracked. Good idea to take a peek inside and see what we have. An endoscope camera attached via USB-C to a cell phone went right in, but could not see the valves. Pulled it out, turned the engine to bottom dead center (BDC) on #7, and take another look. OK, now we can see the intake valves, and they are OK. Top of the piston looks wet (fuel?), but no visible damage. Cannot quite see the exhaust valve for some reason. Push more wire into the cylinder for the camera, no joy. Pull it out, let's try from the other plug hole. Can't. Camera is jammed! 90 minutes of pushing in, and tugging out, no luck. Push in one more time, give it a tug.... it's free! Camera comes out. Yay! Not so fast. Camera comes out, aluminum body of the camera dropped in the cylinder. UGHHH! Time to take a break. Get on Amazon, order a much better borescope, with an articulating 4.5mm end. Idea is to get a better look around, and then "spear" the camera body, turn the articulating arm, and pull it out. Two things on this: New borescope is 10x better than the cheap endoscope. Much, much clearer picture, and the controllable end piece made it easy to look to see that all three valves were intact. It also gave a clear picture that the wet stuff on the piston was oil, not fuel. Second, there was no hope on spearing that camera body. No matter. Oil is likely from past the rings, due to a cracked piston. Engine has to come out and come apart, anyway, so this part of the exercise is now over. Engine is blown. But what happened? More on that later. Out it came for now


Few things here. Those headers? Yeah, they were in the car for just about 600 miles. Notice that the ceramic coating looks about 20 years old and is peeling off. Not too happy about that one. Both headers were about the same. Engine oil came out black as ink, backing up the cracked piston theory. There were no leaks of any kind, any where, so the resealing did do its job, despite the overly short life.

Due to life commitments and a conscious decision to approach this without being angry at it (easy to do, right?), the timeline of this stretched out for two months. Fortunately, a 'spare' M113K had been acquired this past summer. It was an unknown quantity from a non-running 2003 S55, but the idea was to tear it down and have it sleeved and built up for abuse, so condition really did not matter. Now it does. Now it might be the engine savior for a bit. It was decided to treat this as the unknown quantity that it was, and therefore needed to be gone through. Engine was stripped down to the long block to be inspected and resealed. The treatment that the old engine received just this past summer of being resealed and normal wear items replaced happened to this one. The difference was that this engine was remarkably clean inside. Like gorgeous clean for a used engine! Very little varnish, and looking at the bores, no scratches could be observed.





There's those timing cover seals. This was supposedly an 80k mile engine. Looking at it, I agree it was. Those seals, however, are 20 years old. Be aware that *every* CF out there has these, and most of them probably look like this. Expect to start seeing posts about overheating CFs and water in the oil. Only a matter of time. It's a huge job to do in the car, but it is feasible, so plan on this as preventative maintenance on your CF coming up in the next couple of years. BTW, this engine did have trace amounts of the blue coolant in it. Every car I see with the blue coolant seems to have rubber issues like this. I run the (evil) GM Dexcool orange stuff in my project cars with excellent results, even if that makes MB purists mad. It was designed for aluminum and rubber. Back to the main story.

Timing cover seals replaced, front and rear main seals, oil pump chain, tensioner and spring replaced, oil pump check valve replaced, oil pans thoroughly cleaned, and then resealed. I have opinions on this last one, too. The upper pan is a machined flange to the block. It is not a place for the factory RTV. RTV is not appropriate here, even if MB/AMG used it. The appropriate stuff is anaerobic sealer. Yes, that red transparent stuff that virtually all other manufacturers use in these cases. No more leaks between the oil pan and block. I waivered back and forth on the timing cover, and finally used RTV there, but that was only due to the coolant and the head gasket areas. Otherwise, it, too, would have gotten the anaerobic sealant. The rear main seal cover is cast, not machined, so RTV there. New spark plugs, and then it was time to park the two engines next to each other to swap parts. Straightforward, but time consuming. No drama there until the very end. A mistake was made. Turning the engine over by hand, a sharp "pop" was heard. Turning more got a second "pop" until it was realized that the timing chain tensioner that screws into the side of the timing cover was forgotten. Rookie mistake! But I made it. Time to see how badly the cam timing got messed up. First, a new tensioner was threaded in to prevent any more skipping. Getting the tools out, and dialing the crank to 40° ATDC, per the manual, and then the cam timing tools are slid into place. If all is well, the tools will slide into the slots on the cams, and lay more or less flat against the cylinder heads (different tool for each bank):


OK! Finally some good news! The sprockets did not jump time, but rather the slack in the chain was biding up on the loose timing tensioner.

Before reinstalling, one last item in the car to tend to, and that was the steering idler bushing. There was significant play in it, so it was replaced, and geometry rechecked (it was off, too!). Generic steering damper was replaced with a Bilstein. Power steering hoses were pre-emptively replaced, also.




Will move into the next post, as we are out of room for pics in this post!