Hello everyone

I have a 2016 Mercedes E class w212 4matic (03/15), that was previously involved in an accident. The car, since I bought it, had problems but I fixed almost all of them; but one problem remains!
Since sometime, my coolant levels keep decreasing whenever I drive the car, typically I would get "coolant level low" message every two weeks. I went to my local garage and told him about the problem, so he pressurized my coolant system with air and left it for about 2 hours, but not a single drop of coolant has decreased; the coolant level was the same. The garage then concluded that I don't have a leak in my cooling system. So what I did was change my radiator cap, and it appeared to be a little bit faulty when I changed it. Anyway, I didn't get the coolant level low message for about 1 month, maybe? But all this time and before I went to the garage, I kept smelling radiator's coolant in my AC. As I'm driving, I would suddenly start smelling coolant through my AC (when its on) for about 1 minute then it would disappear. Also, when the AC is off and the car is hot, I could feel heat over my dashboard near the windshield and in the AC ventilations. But today, with a cold morning, I pressed my gas pedal really hard from a traffic light, and immediately smoke came out from the AC on the driver side, and when I smelled it, it completely smelled like radiator coolant (the ac was off)!!!! The white smoke (more like heavy steam) kept coming for about 5 minutes until it stopped. I assume it is radiator coolant because that's what's obvious to me from the smell and the disappearing coolant, but what could be leaking coolant vapor into my AC system?? And why is my coolant evaporating in the first place? could it be another faulty cap? I did buy a used cap but when I placed it, I immediately felt the difference between my old and new caps; I also didn't get the coolant low message for about one month, but could've the cap condition deteriorated?
If you have any experience with this or you know what possibly could be the problem, I would appreciate an answer.
Thank you and sorry for the long post.

 

Check heater core maybe

 

Add dye to coolant.
Since your caps are questionable, I would install a Tee on small coolant hose and put pressure gauge on it. That would tell you if your system pressurizes and keeps the pressure. Had something like it on my Ford Powerstroke for different reasons and with pressure gauge tied to side mirror, could observe the pressure during driving.
Also if you have heater core leak, it will show drip over transmission when you go under the car as that is where the drainage goes.

 

I did pressurize my system as I mentioned earlier, it does keep the pressure when the car is off. Anyway, today I went to the dealership and bought a brand-new radiator cap. However, I still smell radiator coolant odor from the AC vents..

 

I went to the dealership and told them my story and they told me it might be heater core too (I didn't show them the car)

But As I mentioned, today was a cold day, so the heat (that I always feel coming from the AC) became visible in the form of thick steam or smoke due to the difference of weather temperature and the heat emitted from the AC vents; note, my windows were down. So this leads me to believe the smoke (steam) wasn't from the heater core, but why is there heat coming from my ac vents and from over the dashboard?? Could that be related to the heater core?

 

Start engine.
PUt heat on HIGH and hottest setting.
Watch engine temp gage.

Smell inside every once in a while.
Look for drips under dash or wet carpet.

Do windows fog over easily and defrost does not seem to work?
Smeel sweet like coolant inside?

Then heater core is leaking.
might be small tiny drip or full blown gusher.

Have it checked.

 

My guess is as good as the other suggestions here. I'm willing to bet that when they did the pressure test for you, the heater was turned off. Thus, no chance to detect the leak at the heater core.

 

The heater core is always open to the rest of cooling system at least on 1 end, so it gets pressurized together.
My guess is that the core might have weak seal on its side and when it holds the pressure cold, getting it hot might open the miniature crack.
But reports say about 1/2l loss a month, meaning couple drops per hr. Such leak would take holding the pressure for a week to show the difference.

 

BTW I forgot to mention that after the first time I started to see smoke from the AC vents, the car became weaker when I step on gas.

Anyway, I went to my local garage and during inspection, the mechanic found transmission fluid in my radiator's coolant!
What could be leaking transmission fluid into radiator coolant?? Any suggestions please?

 

Transmission fluid cooler that is built inside the radiator in front of the car.

 

so to fix that, am I supposed to change the cooler or the whole radiator?
Thanks

 

This is a standard cooling procedure for the transmission and has been used for decades. You will need to replace the complete radiator. I assume the accident was a frontal collision?

 

Yes, the accident is from the front, which also bent my condenser inwards; however it doesn't leak so I didn't change it. The thing is that I already did 13k miles on my car and only this week I noticed transmission fluid in my coolant reservoir. that all happened when my transmission acted up and the smoke suddenly started coming out of my ac vents, which led me to check the coolant and notice the trans fluid in it. It appears that I have 2 problems, one is that the heater core is leaking, which I bought bar's stop leak for it and waiting for it to be delivered. The second is the transmission fluid in the coolant, which am looking for clues why it's mixed in there.

Here is a picture from the time of accident of my car:

 

Transmission acting up may mean you also have coolant in your transmission so you have another job to do. Transmission fluid service.

 

It only acted up once when the smoke first came outside. It felt like the transmission did not know which gear to go in. But since the time that happened, I feel like the car has less power right now when I step on gas.
My mechanic will inspect further my car on Saturday so am just hoping that coolant didn't go into transmission or am doomed.

 

This is likely a result of the amount of transmission fliud you lost into the coolant. My understanding is that these transmissions are very sensitive to the fluid level. Hopefully once you replace the radiator and top off the transmission, you'll be okay.

Just a note - there's no filler tube on these cars. Fluid needs to be pumped in from the drain plug which requires a special adapter (available on Amazon) or be prepared to pay the dealer a pretty penny to do it.

 

After radiator replacement - YOU HAVE TO FLUSH ATF VERY WELL.
Gears don't like to work with water.
The leak might be result of the accident, but those radiator-build coolers do fail occasinally on all brands.

 

Are you ABSOLUTELY POSITIVE it's trans fluid in the radiator? Any chance it's oil? Because if it's oil, this all starts to make sense. If it's oil, you may have a blown head gasket or cracked head. This would allow oil to mix with the coolant, but it would also way overpressurize the cooling system, exploiting any cracks / leaks in the heater core (or anywhere else for that matter) when it's running. Would also explain the loss of performance.

I should point out I've never heard of a blown head gasket or cracked head on these cars, I've just been turning wrenches for 20+ years. Also, once you've repaired a wreck, anything and everything is possible.

 

My mechanic says its gear oil. He identified it from the feel and smell. Besides it's not brown so I dont think its engine oil. Being gear oil might justify my transmission acting up; it only acted up once tho. And the loss of power isn't that significant, just the vehicle feels slightly heavier.

 

Aha, gotcha. I glossed right over the fact that you said you were having trans issues.

 

I have not tried the defroster, but yes my windshield fogs and the car smells like sweet coolant odor; so I guess I have a heater core leak. Now to fix that, I have bought 2 products from Bar's Leaks.
The first product is the Bar's Leak Blown Head gasket seal, here: https://barsleaks.com/product/blown-...t-repair-hg-1/

The second product is Bar's leak heater core Stop Leak liquid aluminum, here: https://barsleaks.com/product/liquid-aluminum-1186/

I've sent an email to bar's leaks asking them whether I can mix both of the products in my coolant or would it cause a problem. I still haven't done anything though.

I'm now confused which product should I pour in my radiator, the blown head gasket seal or the liquid aluminum. On the box of the head gasket seal it also says that it stops heater cores leaks also in addition to head gasket and stuff. The other product is designed for radiator and heater core leaks only, and it is liquid aluminum while the head gasket seal is carbon fibre. So, the head gasket seal seems stronger to me as Bar's leaks advertise, but which should I use, the liquid aluminum or head gasket seal..

My car's radiator is currently filled with tap water to clean the oil residues from the old radiator. I'm thinking of putting the blown head gasket seal for now, and when I put real coolant I put the liquid aluminum heater core stop leak. But I was thinking if whether it will cause some chemical reaction and the 2 products would affect each other, so am not sure what to do.

Bar's Leaks still didn't reply to my email so am really confused. Does anyone have past experience with these products? Thanks

 

All I can think of when I hear pour-in leak stop is back in the '70's when I was trying to desperately keep my car running so I could get to my job. Surely, you can afford to properly fix these problems, right?
You will f***k up this car for life if you pour that crap into your radiator. It sticks to everything inside your motor. Best of luck to you going forward.

 

first confirm heater core is leaking.
If it is REPLACE it.

 

I changed my whole radiator and fixed my cooling system. Although, I still feel heat coming from the ac vents when the ac is off and the windshield does fog up. My mechanic also told me it's probably the heater core too, but idk how to confirm it. Anyway, replacing the heater core is a very hefty job and I currently dont have the money for it. It seems to me like u dont like the stop leak stuff, why? Is it gonna mess up my car? I saw many posts where people are divided into 2 sides, some recommend stop leak and others absolutely hate it, but it seems to me that the haters dont follow instructions maybe.
so what do u think, will stop leak ruin my car?? I already flushed my system 3 times and its clean now, will it still hurt if I used stop leak?

 

to confirm you open it up so you can see it.. and then pressure test system...
Or remove it and pressurize on bench....

Stop leak stuff is temp fix IF it works BUT can do MORE HARM then good by blocking required passages ways inside coolant flow paths.
Could cause you to burn up engine which is worse then adding coolant every day.

FIX IT RIGHT - Save ya money and FIX it right or sell it.