Timing Belt Slippage - Gunk on Sprocket
 

What do you make of this gunk on the crank sprocket?

My timing belt slipped and when I loosened the cover and peeked at the belt, there appears to be a buildup of yellow gunk on the sprocket. I can't find any other examples on the web that look like this.

I had the belt and water pump replaced at a shop about 15K miles ago, so I was pissed when the car had symptoms of a broken belt (starter wouldn't turn it over - an obvious bind condition).

The Chrysler coolant is red, so it can't be coolant, it has to be something else (Edit: it's yellow coolant, and that's what we're seeing here; the reservoir looks red from the outside, but it must be stained on the inside from the original coolant). One thing I noticed is that the shop put some kind of silicone sealant on all the edges of the timing cover, and I'm thinking maybe that was a bad idea because if the crank seal or water pump leaks it would flood the lower part of the chamber and submerse the crank sprocket. Does that sound like what I'm seeing here?

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Isn't there a weep hole below the sprocket? I haven't removed the balancer yet to see, but there has to be a way for coolant to escape when the water pump leaks. Maybe the hole is clogged up.

That yellow gunk looks like the result of water mixed with oil. The engine has about 130K miles, but it has never leaked anything except when the original water pump leaked.

OK - I went back to look at it in the daylight (too much midnight mechanic work) and the yellow seepage/growth is coming from under the water pump pulley and dropping right onto the sprocket, and then getting jammed into the splines by the belt. What a horrible design. The gunk is caked up so thick the belt splines have no way to lock in.

At any rate, the "gunk" feels acidic when you rub it between your fingers, and looks the same color as the foamy junk you see when oil mixes with coolant. I guess my next step is to pull the pump and see what the coolant looks like inside the block.

I had a suspicion the water pump leaked from day 1 after the shop replaced it because we have had to add coolant numerous times since then. The pump and belt are only about 2 years old, and my wife doesn't drive this car very far.

What's the "common" cause of oil in the coolant for these engines - head gasket?

Gunk is what is left of the leaking antifreeze as the water boils away on the front of the engine. I doubt very much you have oil in the coolant. Add some water to the gunk, bet it reconstitutes into antifreeze.
Head gaskets rarely fail on these engines.
There is a weep hole at the base of the water pump bet it is the source of the leak.

That's good to hear. Is this fairly common on these engines? I swear I must have looked at every photo on the Internet and I never found one that had a sprocket embedded with gunk like mine. I must be special.

I looked at the oil cap and the dipstick and the oil looks very clean (Mobil 1 synth). The coolant reservoir has clean coolant in it, but I'm waiting to see what's behind the pump before I declare the head gaskets leak-free. I did replace the radiator and thermostat about a year ago because the O-ring on the thermostat broke and got lodged in the spring. I never had that kind of problem before they started putting O-rings on everything!

I was kind of thinking the coolant tube that runs under the manifold could be a possible leak point (read many posts about its O-ring issue too), but I can't see any evidence of leakage up there and there is a definite blob of gunk under the water pump pulley.

I picked up a puller kit and a pusher kit for the balancer this morning so I'll be finishing the tear down tonight.

The biggest question in my mind at this point is how I'm going to re-align the crank and cams on the timing marks due to the slippage. There is definitely some interference right now, so after I get the belt off, can I simply spin the cams around to their timing marks to close all the valves? The crank won't turn freely until the valves are all out of the way.

I don't think there will be any bent valves because my wife said the big slip happened when she was trying to start the car, which means the starter was doing all the turning and not the engine. The crank turns very easily right up until a piston hits a valve, then it turns easily back the other way too.

Was the repair shop right to "silicone" the timing covers? Since I wasn't the first one to tear into the timing I don't know what the factory install looked like. Right now I plan to scrape that stuff off and leave it off.

Oh, and I'm picking up a new pump today - not a remanufactured one. I don't want to do this again any time soon.

More Pics!

Stain below water pump pulley. There was a big blob of that stuff under there when I first opened this up, but I used a long screwdriver to grab a scraping I could use to try and identify it. You can also see some of the white sealant the shop added to the cover.

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Oil filler neck and cap. Looks clean.

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Dip Stick. Can't get much better looking than that.

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Coolant. Turns out I have the gold coolant in here.

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Trans Fluid, still looks and smells like new.

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It looks like I have valve issues because I can't get the crank to spin up to the TDC mark. I can spin the crank either way with no trouble but it keeps hitting something that sounds like it's on the passenger side in the rear. I tried moving the cam sprocket to the timing mark but it doesn't help.

What is my next move, pull the valve cover? I haven't removed spark plugs yet.

I'm pretty mad at the shop right now. The failure appears to be due to using silicone on the water pump. When I removed the pump there was gray silicone all over the place, and it was thick enough to allow the O-ring to seep on the left side of the plate.

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Here's one of the pieces of gook that peeled off the water pump. FAIL.

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The inside of the engine looks brand new. You can see more of the silicone mess here. I had a hard time removing the pump because of all the glue.

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Tensioner looks original. The white sealant they used on the cover doesn't go all the way to the bottom, so that is good IMO. Any liquids that made their way to the bottom should have been able to drain.

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What a mess.

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Not sure if the pump seal was leaking too much but there is evidence of some leakage. I think the primary failure was the silicone along the left edge of the flange though.

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WOW what a mess, all due to silycone used by moechanoc causing the oring to fail. Interference engine almost a sure bet there is valve damage.
visit Welcome - Chrysler 300M Enthusiasts Club and search around for more info....

Well fellers, I think the fat lady just sang. I went about removing the spark plugs so I could stick my endoscope down there and see how bad things were. I started at cylinder 5 and worked up to cylinder 1.

Cylinder 5: Some nicks in the surface of the piston, obvious contact, but hey, I thought this looks pretty minor, maybe I lucked out.

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Cylinder 3. Pretty much the same as 5. So far I'm optimistic.

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Cylinder 1. OMG. That does not look good. Now I'm doubting my wife's story about the car running fine when she parked it. How did this happen from just cranking the starter. Ok, I thought, I was planning to remove the heads anyway - I can still save this old girl.

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I move in closer to the broken valve - WHAT?!? A cracked piston!!!!! NOOOOOOOO!!! What, are these things made of Chinese pot metal or something? Facepalm. After a moment of silence, I put my tools away and for the first time realized my son will not be getting this old Chrysler handed down as his first car. And to think I just finished doing the evaporator replacement job on this thing, which requires removing the entire dash. It's a sad day at my house. And my wife wonders why I always insist on doing everything myself, but here is a great example of what happens when you hire a "professional" to do the work for you.

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