COOLANT SMELL
Thread Starter
Junior Member
Joined: Nov 2015
Posts: 40
Likes: 5
2019 C300
COOLANT SMELL
Hey everyone. Got a good deal on a 2007 GL450(second one) two weeks ago, and I found out it was in an accident (nothing major) but I have a non stop coolant smell. On the ride home there was coolant everywhere. I pulled over at a 7Eleven and it was the overflow tank. So not taking any chances, I replaced it. Everything was fine for 4 days, but I still had that smell. I noticed the auxiliary pump would stay on as long at the car was on. and the smell gets stronger when the vehicle is warmed up and its losing coolant somewhere. I thought it might have been the head gasket, but there is no white smoke coming from the exhaust, No coolant on the dip stick, and I changed the oil and nothing there either. Can someone point me in the right direction. Really trying to avoid taking it to Mercedes and spending hundreds on a diagnostic that might be wrong.
Problems: (1) Coolant smell in and out of truck. Mostly in engine bay and very strong inside even with air off
(2) Auxiliary water pump stays on once the ignition is on. only shuts off when the truck is off
(3) Losing coolant
Problems: (1) Coolant smell in and out of truck. Mostly in engine bay and very strong inside even with air off
(2) Auxiliary water pump stays on once the ignition is on. only shuts off when the truck is off
(3) Losing coolant
Thread Starter
Junior Member
Joined: Nov 2015
Posts: 40
Likes: 5
2019 C300
No droplets. I sat in the car today. didn't turn it on. just put it in the on position and you can hear the auxiliary pump running then the smell inside the cabin hit me again. but the engine was completely cold. no air on or nothing
Senior Member
Joined: Mar 2017
Posts: 258
Likes: 50
R320, Astro, JSW, ST4
I had a leak most of last year, replaced a number of hoses in succession...
To be sure where the coolant is going, you must pump up (pressurize) the coolant system.
A cheap kit for this can be found at Harbor Freight, or can be had at parts houses.
Make sure the system is full to reservoir level, you may have to warm it up to operating temperature (thermostat opens) then turn it off and let it cool to top it off again.
The test is best done with cold motor, because rubber shrinks (hoses tighten up and seal around fittings) when warmed, unlike most materials which expand when heated.
So leaks will show up best dead cold.
You have to be ready to look everywhere.
I found coolant was pooling under the brake booster in my car on a flat place behind wheel well - it turned out was short hoses between engine compartment sound panel and the firewall.
(Lines go to the heater core but have short hidden sections between firewall/interior and what looks at first like the firewall, but is an extra layer in the engine compartment)
I had to remove the windshield wiper stalks, plastic valence panel below the windshield, and a small sound panel in the engine compartment to get to these.
Actually, more than that...
The panel in the engine compartment has plastic pipe fitting comings through it.
My leaks were from the short hoses behind and connected to the plastic pipes - the stock clamps cannot be tightened or adjusted.
I'm not positive that GLs and MLs have this extra void between the firewall and the engine, but I bet they do - to deaden the sound and provide a chase for the hoses.
I recall the MB hose clamps being praised when I was a kid - but I realize now they do it their way Solely for speed of assembly.
To be sure where the coolant is going, you must pump up (pressurize) the coolant system.
A cheap kit for this can be found at Harbor Freight, or can be had at parts houses.
Make sure the system is full to reservoir level, you may have to warm it up to operating temperature (thermostat opens) then turn it off and let it cool to top it off again.
The test is best done with cold motor, because rubber shrinks (hoses tighten up and seal around fittings) when warmed, unlike most materials which expand when heated.
So leaks will show up best dead cold.
You have to be ready to look everywhere.
I found coolant was pooling under the brake booster in my car on a flat place behind wheel well - it turned out was short hoses between engine compartment sound panel and the firewall.
(Lines go to the heater core but have short hidden sections between firewall/interior and what looks at first like the firewall, but is an extra layer in the engine compartment)
I had to remove the windshield wiper stalks, plastic valence panel below the windshield, and a small sound panel in the engine compartment to get to these.
Actually, more than that...
The panel in the engine compartment has plastic pipe fitting comings through it.
My leaks were from the short hoses behind and connected to the plastic pipes - the stock clamps cannot be tightened or adjusted.
I'm not positive that GLs and MLs have this extra void between the firewall and the engine, but I bet they do - to deaden the sound and provide a chase for the hoses.
I recall the MB hose clamps being praised when I was a kid - but I realize now they do it their way Solely for speed of assembly.
