[asus389]

My e90 is in great shape but for a while now I have been smelling coolant in the front passenger side of the engine bay near the top of the radiator. I have had it in for service twice and it reportedly passes a pressure test and the mechanics (one dealer and one indy) say they inspected it and don't see any traces of coolant. I suspect there is a small leak that isn't showing up easily. I have read that you can put UV dye in the coolant via the expansion tank, drive the car for a couple days, and this might help finding hard to spot leaks. Has anyone done this? Was it helpful? Is there any risk to my car from putting this stuff in there? Does it stay in there forever or should I drain/refill it?

[GATORB8]

May want to check the coolant return line. It runs over the top of the radiator, just under the front of the air intake ducts (on the N54 at least). It's plastic and rubber and tends to crack.

Number seven here:
http://www.realoem.com/bmw/enUS/show...diagId=17_0351

Can you see any liquid? The coolant stays "wet" for a day or so, then dries with a white-green haze.

[asus389]

I don't see any coolant coming from that line. However it passes over the area where I get the coolant smell from. I do see some white residue near or coming out of what looks like some sort of vent or indentation on the top of the radiator. I guess this could be coolant, but if so I'm not sure where it is coming from because from what I can see the radiator doesn't appear to be leaking?

[GATORB8]

Originally Posted by asus389

I don't see any coolant coming from that line. However it passes over the area where I get the coolant smell from. I do see some white residue near or coming out of what looks like some sort of vent or indentation on the top of the radiator. I guess this could be coolant, but if so I'm not sure where it is coming from because from what I can see the radiator doesn't appear to be leaking?

Is the bleeder valve (the plastic phillips head "screw) tight? If not, it can spit after the car warms up.

[asus389]

Originally Posted by GATORB8

Is the bleeder valve (the plastic phillips head "screw) tight? If not, it can spit after the car warms up.

As far as I can tell its fine. There isn't any white residue on either the overflow tank cap or bleeder screw. Maybe I should remove the radiator fan and look at the back side of the radiator, but I'm not sure what coolant looks like on the back of a radiator? Its easier to see on black plastic parts.

[Efthreeoh]

Has the car been losing any significant amount of coolant? Meaning is the low coolant light coming on repeatedly? If not, then your are just smelling coolant vapor. If it were my car, I'd first replace the coolant reservoir cap with a new one as step two of the diagnosis. The mechanics pressure tested the cooling system, but probably did not pressure test the cap.

And just to be clear what you call the "overflow" tank is really the coolant reservoir, which is under pressure. Overflow tanks are not pressurized.

[mweisdorfer]

Putting a dye in the AC system is standard procedure for finding a leak in that system. The reservoir tank is often a culprit for leaking in the e90.

Just remember, ever time you open the cap on the reservoir tank, you have to re-pressurize the system.

[asus389]

The coolant seems to be going down very slowly. It takes a couple months for the measurement stick to drop noticeably below the top of the cap. And yes, I think its the vapor I'm smelling, and thats why I am concerned. Its not so good to breathe.

[Efthreeoh]

Originally Posted by asus389

The coolant seems to be going down very slowly. It takes a couple months for the measurement stick to drop noticeably below the top of the cap. And yes, I think its the vapor I'm smelling, and thats why I am concerned. Its not so good to breathe.

Do you smell coolant while in the car driving? If so then that could mean the heater core is leaking, but again the system was pressure tested. If you mean smelling it when the hood is open then that is not a concern.

[asus389]

I smell it from the front of the engine bay on the passenger side after the car has been driven for 10-15 minutes. Sometimes its a lot sooner. I am fairly confident its not the heater core because my AC evaporator was replaced a few months ago and I asked them to check the heater core and replace it also if it was leaking. They told me there was no evidence of the heater core leaking. The AC evaporator had PAG oil and UV dye all over it.

I also smell antifreeze from the area under the power steering reservoir. This happened after they replaced the evaporator. I can only guess its because they spilled some when disconnecting the heater hoses. But the thing that concerns me about that is they have gone back to flush the engine bay with water multiple times (and I have done it myself a couple times) and it seems to have no impact on the antifreeze odor in either area. I understand that it takes a while for antifreeze to go away after a cooling system repair, but in this case it would be nearly a year. Is that normal?

The concern about the antifreeze vapors getting into the intake for the HVAC is based on the fact that on my old BMW, when the VCG leak occurred it was fairly obvious as you could smell the burning oil when it dripped onto the exhaust from the inside of the cabin when the heat or ac was on. This was despite the air filter, etc. So I suspect that even though a heater core leak would obviously get antifreeze fumes in the cabin, I don't think 100% of the fumes from other leaks in the engine bay are filtered out before they get to the HVAC.

[bimmerboyE92]

My 128i suffers from a pin hole leak through the engine block in that area. Found your post while looking for others with a similar problem.

http://www.1addicts.com/forums/showthread.php?t=1339098