dfstell

As the title says...... I've got a small amount of smoke on the passenger (i.e. right as you are driving) side of the engine bay. It's only at start up and seems worse from a cold start than a warm start. The couple of times I've seen the smoke with the hood up it is coming off the descending exhaust manifold. To me, it smells like coolant, but I'm not sure how there would be a coolant leak there. I don't see any oil or anything coming from the injectors and there is no dripping of anything on the ground. All fluids are proper levels and the only error code it has thrown is the the thermostat isn't letting the car reach operating temp (which I assume means it is stuck open). I'm going to replace the thermostat. My initial theory was that the thermostat being stuck open allowed a rush of coolant through the thermostat on start-up and some was leaking out......which burned. But I'm not sure that theory works with the location of everything since the radiator hose goes more to the driver (i.e. left) side of the engine bay. The exhaust has no smoke at all of any color.

Any ideas? I just hate to take a Mercedes into the shop with a mission to "find what's wrong". I mean, it's a 2011 with 110K miles. It's a weekend mulch and kid hauler, not a daily driver. It has odds and ends acting up. But smoke isn't good. I'd rather know what it is.....then decide if I can fix myself or just want to pay someone to fix THAT.

eric_in_sd

Can't be too hard to find. Clean the motor, run it to dry it thoroughly (and bring coolant temp up), leave it sitting overnight, and inspect in the morning. Search with a borescope if you need to. You can get a cheap USB borescope, and they're useful for all kinds of household tasks, like peering inside your teenager's ear to see if it's true he has no brain.

kombifan

What color is it?
Blue, white, grey?

Has the intake manifold been replaced on yours?

dfstell

Gray smoke and the manifold has not been replaced to my knowledge (but I did not buy it new).

dfstell

Good suggestion. Thank you!

eric_in_sd

Dude said it smelled like coolant
Oil would stink like crazy

TX07GL450

Clean that side of engine THOROUGHLY. Use engine degreaser etc.
Then stuff white cloth or papertowel in there overnight.
remove it in morning and observe it in detail. Any fresh stains / drops ?
Start the engine, and see if there is still smokes on that side.
if it is not that bad, and you can't figure it out, see if you can live with it for now. It will get worse and become easier to diagnose.
You can also place a cardboard on the floor, right below engine for the whole week. and then observe it on weekend before you take it out
Good Luck

dfstell

Just to close the loop on this.....it's a small leak around the valve cover on the back of the engine. It's not even a very big leak and wouldn't even be easily noticeable if it wasn't dripping right onto the exhaust manifold. :/

Not the easiest thing to get at either.

eric_in_sd

Was it coolant?

JamesMitchell

I had a similar mysterious smell/no leaks on the floor issue recently. For me It turned out to be the oil pvc breather. It could be the oil pvc breather and/or the one cam plug on the passenger side or the two cam plugs on the driver's side. These are maintenance items and go bad over time. I replaced the oil pvc breather and the smell was immediately gone. This was the part number 2720100631. I ordered one on Amazon as an original OEM Mercedes part for $53. FCP also has a kit which in they supply the pvc breather, and the three cam plugs and replacement screws in a kit for about $85. If the leak is on the passenger side and toward the rear of the engine (near firewall), I'm betting it's the pvc breather and/ or the cam plug. But if it is distinctly smelling like radiator fluid, it's likely another problem.

If you think it may be the pvc breather and/or or the cam plugs, there is a video that shows how to replace them. It's not that hard. I would rate it a 2/5 as far as difficulty. Will need a T30 star bit to get the breather out and just a flat head screwdriver to get the cam plugs out. Here's the video: Good luck.

Please let us know how it works out.
James

dfstell

Nope.....it's oil. :/

dfstell

That is super helpful. The reason I don't have any drips on the floor is because it is dripping right onto the exhaust and it's only dripping when the engine is running and oil is pumped up to the top of the engine. Honestly, if it dripped any other place, nobody would know because it would just be dripping onto the road as I drive around. And I'm 4500 miles since the last oil change and it's not even down a 1/2 quart.......so it isn't dripping much. And the silly vehicle only has like 80 quarts of oil in it (I know, I know.....it's 9.7 quarts, but you get my point. What ever happened to engines that took 4-5 quarts?)

I actually have half a mind to just rig up a thing to guide the drips elsewhere, lol, and then just watch for a puddle or the oil level to drop.

I DO like your solution as the next thing to investigate just because it is bolt-on parts and I'm fine with that. Much preferable to a valve cover gasket.

And I hate those stupid star bits.

eric_in_sd

Cam housing plugs & separator, most likely. Possibly valve cover ("cam housing") gasket. It's an easy fix and they best case last ~50k miles (OEM, 20K aftermarket). At 70k miles my OEM housing plugs were falling apart when I removed them.

See my thread about applying sealant; I'd do it even if you use the OEM. It's a sick joke they use injection molded plastic that falls apart in the heat and oil.

JamesMitchell

eric_in_sd

Great tips.
I just swap around with a clean rag; the oil seep is easy to spot.
I'm not sure you need the Loctite. It won't hurt, but maybe because the parts are aluminum, there doesn't seem to be much issue with bolts wandering out. There are washerless bolts all over that motor. Maybe it's the bushing the bolt goes through; it compresses?

Don't overtorque into that aluminum, btw!

Max Blast

Check the passenger side exhaust manifold for oil drops before you fire it up next time. Then figure out where the oil is coming from -valve cover gasket, probably.

dfstell

This is very sage advice. :/

Just to update since you guys have been helpful......I'm now fairly confused.

The vehicle was throwing a "can't reach operating temperature" error, so I went to change the thermostat. Seemed fairly simple.....and it really is.....as long as you have respect for those bolts. Oddly, the bottom bolt came out a little cross threaded and stiff (unsure why that is. I got the vehicle with 40K miles and that seems soon for anyone to be replacing a thermostat and it isn't on the Carfax). Against my better judgement, I tried to get it back in. In my defense, I was trying to finish a job while it was sleeting on me, lol. Anyway......it got stiff, I tried to muscle it, the ratchet slipped and boogered the head of the e-torqx bolt. I walked away in disgust.

Waited a day for spilled coolant to evaporate and started it. Hoped it would be a slow leak....but no. More like a "Pump it all out onto the ground" leak. On the plus side, the new thermostat works properly.

So, I made an appointment at the local Auto Werks type of place. It was 17 degrees when I had to drive over, so it made it without needing to stop to cool off.

Interesting tidbit #1: No burning smell on this drive over. As you can imagine, I was mostly focused on the cooling situation, but there was none of the past burning smell coming from the passenger side.

The shop fixed it. Not too horrible. $600. They drilled and put in Heli Coils and everything is buttoned up now.

When I went to drive home, I immediately got a "low coolant" warning, but there is no leaking. I suspect they maybe just didn't refill it all the way? It cools fine and stays in the 80-100 window.

Also....again.....no smoke or burning smells. The heat works again (and it didn't before when it had just pumped all the coolant out onto the ground). I've driven it 5 times now on little around town trips. No smoke or smells.

Which is making me doubt the original though that it was engine oil. I didn't actually put my fingers on the hot exhaust manifold. But there seemed to be some wetness on the heat shield below the manifold. That that seemed like greasy engine oil.

So......I'm confused. On one hand, I'm glad it is partially fixed. On the other, I'd like to know why it isn't smoking anymore. Was it MAYBE not engine oil and was some coolant line.....and it's not dripping because the reservoir isn't full???? Was it possibly a loose valve cover and the tech got sick of the burning smoke of oil dripping on the exhaust and he just torqued a bolt to make it stop???? I kinda hate to call them to ask questions about something I told them I didn't want them to mess with.

eric_in_sd

Part of the reason it's important to stay on top of the vehicle's condition is you can have overlapping and compounding problems. You're lucky the motor didn't self destruct from running on no coolant; fortunately, it was cold out , there probably was a reserve of coolant in the block, and, remarkably, motors aren't all that sensitive to coolant loss overheating. The thing that gets them is oil overheating or, in the old days of iron blocks and iron heads, warping.

You probably have multiple issues that are making the diagnostics confusing. Proceed methodically; fix one thing at a time.

You have the thermostat replaced; the heli-coils are actually an improvement over threads cut directly into the aluminum. So you're good there. My guess is corrosion had frozen the bolt threads to the aluminum, and so the aluminum gave way when removing the bolt. I almost had a heart attack when I thought I'd stripped spark plug threads, but it turned out the plug appears to be designed to give way before the threads. Removing the plug threads was interesting but not too difficult.

The coolant level sensor is in the reservoir. They probably refilled it with coolant and didn't let it idle long enough to burp out the air bubbles. Just top it up. You could ask them to, so you don't have to buy a whole jug of the stuff. Or just buy a jug of 50-50 mix at Autozone (Zerex G-5, remember) because you will have to top up the coolant more in the next 150k miles.

Then get back to changing those housing plugs. It's easy, and I've even posted a thread on gluing them in with Permatex black. Do NOT use the Dorman plugs; the new version has an aggressive seal / flange and the plugs back out on their own. It's stupid to pay $$ for injection molded plastic with overmolded rubber, but the grief from the plug walking out on you is not worth it.

I bet you had both a coolant and oil leak. Both can be erratic.

Just be patient and methodical. It may seem like a neverending story sometimes, but you really will get it done.


P.S. If you're ever again stuck with a stripped bolt, you can basically glue the bolt back in with Loctite, and silicone the thermostat housing in place. Wait a few hours - more is better, up to 24 or so; let the silicone cure - and then drive to the shop, or to the parts store to get your heli-coils and drills. Run the motor at low rpms to keep the water pressure down, and watch out for a sudden gush of steam from under the hood.