Coolant smell, no leak, running too lean?

[m3f_idriveastick]

I've searched up and down, left and right. SOMETIMES, after a drive, I smell coolant. However, I immediately look/watch/listen under the car and see no drips, hear no sizzles, hear no pressure leaking, etc.


I did notice that my rubber intake boot was cracked (common issue, it seems). Could my theory that the motor running too lean due to more air after the MAF is causing coolant to either burn or get pumped through non-stop thus causing the smell? As I said, it's only sometimes. I cannot pinpoint what conditions cause it--it's random (soft driving, harsh driving, long trips, quick trips).


Any takers on my theory? I just changed the boot and I'll go for a drive tomorrow afternoon to try to get some coolant smell--hopefully I get nothing and this was it!

[m3f_white-hot]

One has nothing to do with the other. If you are smelling coolant but the level is not getting lower and there is no obvious drips then you likely have a pinhole leak or weeping hose that only allows coolant to pass when under full pressure. Go to your favorite autoparts store and rent a pressure tester and see if you can find it. BTW BMW coolant (you are using BMW coolant, aren't you?) will dry to a white trace so take a close look at all hose ends and around the radiator. I have had hoses begin to leak after having been replaced a few months before. I generally check all the clamps every couple of months.

[m3f_idriveastick]

One has nothing to do with the other. If you are smelling coolant but the level is not getting lower and there is no obvious drips then you likely have a pinhole leak or weeping hose that only allows coolant to pass when under full pressure. Go to your favorite autoparts store and rent a pressure tester and see if you can find it. BTW BMW coolant (you are using BMW coolant, aren't you?) will dry to a white trace so take a close look at all hose ends and around the radiator. I have had hoses begin to leak after having been replaced a few months before. I generally check all the clamps every couple of months.

Yeah, I've looked multiple times for dried up, white, crusty shit: nothing. Yes BMW coolant. Cooling hoses, thermostat/housing and radiator were replaced about 50k miles ago.


I understand the intake has nothing to do with coolant, but I do know that a lean engine will run hotter. Heat is controlled with the cooling system which relies heavily upon the coolant (among other things).


My train of thought was this: ECU thinks it's getting X air, but more than X air is coming into the engine due to the rip in the rubber, thus causing a lean running motor. In turn, the engine is hotter due to a lean state. Thus, the cooling system has to keep up with the engine's heat output (I notice the mechanical fan is on a lot; fan clutch is fine as is the temp switch).


I understand I shouldn't smell any coolant, but due to this possible lean/hotter-than-normal scenario, is this a special case? Perhaps a component of the cooling system is operating at a higher than normal temperature and is causing some warping or dis-formation of some sort?


Hey, I'm really reaching here but I've seen/heard crazier things.

[m3f_98///M3]

Your engine may be running lean, which would be hotter, yes. But the thermostat opens at a certain temp (if it works correctly) and will circulate coolant as needed. In hotter climates it has to keep up, and it's no where near as hot as summer right now. So I'd have to say that likely has nothing to do with the coolant smell. But by all means, change the elbow and see if that makes a difference. How's the coolant level? If you aren't losing an appreciable amount I'd say your theory would go out the window, but that's just me.

[m3f_white-hot]

You are reaching. The car can fully overheat and you might never smell anything till coolant blows out the tail pipe. While a lean condition will cause a higher engine temp it will likely just reveal a defect in the cooling system and not necessarily create the defect. Also, the mechanical fan is controlled by RPM, not temp.

[m3f_idriveastick]

You are reaching.

Yeah, yeah..

The car can fully overheat and you might never smell anything till coolant blows out the tail pipe. While a lean condition will cause a higher engine temp it will likely just reveal a defect in the cooling system and not necessarily create the defect. Also, the mechanical fan is controlled by RPM, not temp.

By RPM? Didn't know that...thought it was engaged/disengaged somehow electronically. Hm. Then again, this is my first (of three) e36 that I actually run the mech fan. Had SPAL's in my other two. I guess you learn something new every day.

[m3f_idriveastick]

How's the coolant level? If you aren't losing an appreciable amount I'd say your theory would go out the window, but that's just me.

Same as the day I bought it a couple of months ago--a bit over (1 inch +/-) the cool line when cold and a bit under the cool line (1 inch +/-) when warm/hot. I run it almost every day of the week varying from 5 miles to 80 miles per trip. I purposefully look under the car after leaving almost every parking spot on each trip since it's new to me and I need to find leaks the PO may not have mentioned. Oh, and I'm paranoid.

[m3f_fiveightandten]

FYI, unless you're using a mirror, you're not checking well enough for leaks. Get one of those small telescoping/tilting inspection mirrors at an auto parts store. Check under the thermostat housing. Check the underside of hose connections. Pull the belt off so you can remove the water pump pulley and check the water pump. Check the radiator end caps. Check everything. If you smell it, it's leaking.


You may have to pressure test it or dye it to find the leak.


While the engine bay is warm, tighten up hose clamps. Don't go crazy, but you can crank them down much much harder when the rubber is soft, so keep that in mind. Sometimes you'll need to tighten them while it's warm. Just be gentle.


Especially with a small leak, it can burn off near the point of origin so it's barely noticeable. The cooling fan can blow it around too (as well as airflow through the engine bay), so look for any traces of white splattering at all.

[m3f_Roland H]

WHERE do you smell the coolant? If it's in the cabin, you need a new heater core...

[m3f_idriveastick]

WHERE do you smell the coolant? If it's in the cabin, you need a new heater core...

Nope, it's after I open the door or if I come to a stop with the windows down or am reversing into a parking spot with windows down. I was thinking heater core too but it's not inside.

[m3f_white-hot]

Sounds like a pinhole leak during full system pressure only to me. As Nick said, you need a mirror to see all the hoses and other likely surfaces. There are 5 more "hidden" hoses, 2 go to the TB and 3 to the heater valve/core. Look for a bulging hose or trace of white.

[m3f_idriveastick]

Sounds like a pinhole leak during full system pressure only to me. As Nick said, you need a mirror to see all the hoses and other likely surfaces. There are 5 more "hidden" hoses, 2 go to the TB and 3 to the heater valve/core. Look for a bulging hose or trace of white.

Thanks for the advice guys. I'll give it a look soon. I am not overly concerned, because I did a very detailed inspection, with a mirror and flashlight, when I bought it. Not to mention the coolant level not declining nor seeing any puddles under the car. Maybe these damn NYC metro area streets and their potholes jarred something loose a bit.