Hissing from engine/not coolant but temperature spikes
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Joined: Jul 2022
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ML250
Hissing from engine/not coolant but temperature spikes
Hello,
ML250 owner here, car after about 30 minutes the temperature gauge will spike up to 120. Will see steam coming from the left side of the bonnet the AC will no longer run hot and a sweet chemical smell runs through the AC. When I go under the bonnet i can hear a hissing sound but I can't quite see where it's coming from its around where the bonnet/dashboard meet.
I've had the coolant checked and the merc tech said it wasn't that.
Help!
ML250 owner here, car after about 30 minutes the temperature gauge will spike up to 120. Will see steam coming from the left side of the bonnet the AC will no longer run hot and a sweet chemical smell runs through the AC. When I go under the bonnet i can hear a hissing sound but I can't quite see where it's coming from its around where the bonnet/dashboard meet.
I've had the coolant checked and the merc tech said it wasn't that.
Help!
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Sherlock puzzle investigation
Hello,
ML250 owner here, car after about 30 minutes the temperature gauge will spike up to 120.
Will see steam coming from the left side of the bonnet the AC will no longer run hot and a sweet chemical smell runs through the AC.
When I go under the bonnet i can hear a hissing sound but I can't quite see where it's coming from its around where the bonnet/dashboard meet.
I've had the coolant checked and the merc tech said it wasn't that.
Help!
ML250 owner here, car after about 30 minutes the temperature gauge will spike up to 120.
Will see steam coming from the left side of the bonnet the AC will no longer run hot and a sweet chemical smell runs through the AC.
When I go under the bonnet i can hear a hissing sound but I can't quite see where it's coming from its around where the bonnet/dashboard meet.
I've had the coolant checked and the merc tech said it wasn't that.
Help!
trouble T: 120°C = 250°F
target T: 200°F = 93°C
It's a bit confusing that your indy specifically tested hissing is not coolant but engine is physically overheating....
The hissing could be an air leak from ether vacuum pump or crankcase pressure.
Any chance ciolant circuit was worked on and not properly burped to prevent pump cavitation.
Bonnet near dash has both plastic coolant pipes and vaccum hoses...
Help yourself with the purchase of a MB scanner to read available faults.
Furthermore use a professional MB specialist shop to poke your car, not the local tire shop. These cars are built to generate lots of curved *****. They need very specific fluids as well - Generic green coolants are expensive mistakes!!
Last edited by CaliBenzDriver; Nov 10, 2023 at 10:02 PM.
