I have a 1980 240D that had a bad leak from the bottom of timing chain tensioner gasket. A few days ago I replaced that gasket, which was kind of a pain as it involved removing the thermostat housing from the block and having to redo that gasket too. As I understand (and because there didn't seem to be much on the internet about doing this job or describing other procedures), I simply unbolted the tensioner, cleaned the gasket area, applied a very thin layer of silicone gasket sealer*, and installed the gasket and tensioner again. I torqued the bolts down to 24 nm, and I did not touch the large bolt in the center of the tensioner.

Anyway, the problem is the next day when I started the car up and long story short it is still leaking . The weird thing though is how it leaks. It doesn't seep or drip but about every 5 seconds or so, it kind of squirts a little bit of oil. So after about 5 minutes of idling, there will be a little pool of oil, about 1.5" in diameter, sitting on the little shelf where the alternator bracket bolts to the block.

So now I'm trying to consider whats up. I mean i suppose it could be that I just messed up installing the gasket , but I have successfully done many gaskets like this. I also read a horror story of someone's mechanic cross threading the tensioner bolts, but I really don't think this happened either because i almost entirely screwed these in with one hand, while holding the tensioner to the block with my other hand.

Does anyone have any thoughts about this? Is this actually a more complicated job than remove and replace? Could it be the tensioner actually also had a crack or something that i might have noticed when it was off? I've just never seen something leak like this before.

Thanks in advance for your help

* I know everyone has an opinion on using this stuff, but I just use a small amount to make up for small indents or unevenness that might exist on parts this old. And like i said, I've never had anything leak like this after replacing a gasket this way.

 

It's possible that your leak isn't coming from the timing chain tensioner, but somewhere above it. Clean it off carefully, and run the engine while looking for the leak. Start from the highest point in that area, and work down. Where you see an oil trail starting is where the leak originates, not where it pools in a cavity, or runs along a ridge.

 

Hey thanks for the response. I have the area pretty clean in that, so it was clear the leak was definitely from the tensioner and not the valvecover. It turns out the oil was leaking out the top side of the part, running down the slant, and then dripping off the edge. The engine fan was then blowing it back so it looked like it was squirting out the bottom.

Anyway, I ended up removing the tensioner, smoothing out the metal faces again (including a scratch i hadn't noticed before ), and reinstalled the part. But thats not the end of the story. Sometime between torquing it down, and letting it sit before rechecking the torque, a hairline crack seems to have developed on the right side of the tensioner mount . It essentially runs along the front face from the top to the bottom, about halfway between the right bolt hole, and the big bolt in the center.

Well, just to check, I did idle the car for a few minutes, and it doesn't seem to be leaking now. Though obviously i shouldn't settle on this as a solution, so i guess my question is "Its probably time to get a new tensioner huh?"

I do have the tensioner from an engine which ran out of oil, though it seems there was still oil in the tensioner when i removed it . Plus the metal face on this tensioner looks in very nice shape, with no dings or scratches or anything. Is this one probably in good shape to use or is it probably damaged like the engine it came out of?

 

About the sealant, I have to say that Forced is right, it's best not to use gasket sealant whenever possible. As far as the other tensioner, I haven't been inside one of these engines. A general rule is to check all moving parts for freedom of movement, gaulding, or excessive wear/looseness. If all checks out ok use it by all means.