OM642 overheating
Thread Starter
Newbie
Joined: May 2021
Posts: 6
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2009 GL320
OM642 overheating
Hello All, I have a serious head Scratcher.
I have a 2009 Mercedes GL320 Bluetec with 230K miles.
I removed my Thermostat and at idle/normal driving around town my engine temperature stays around 95 deg Celsius, and ONLY when I’m going 70-80 MPH up a Large Hill on the Interstate my engine temp gauge quickly fluctuates between 90-120 deg Celsius.
My Coolant Temperature Gauge has NEVER NEVER NEVER ever went over 90 deg Celsius, in times past while even going up Steep Mountain’s at 85 mph, I know this true because i watch my Coolant temperature like a Hawk.
I have already replaced...
Water Pump.
Removed my Thermostat.
Replaced Coolant Temperature Sensor.
The Cooling Fan seems Normal runs Very Fast when temp goes over 100 deg Celsius.
And I’ve already considered a Air Pocket in the engines Cooling System, but I on 5 different occasions I pulled and held Vacuum on the Cooling system before refilling it with coolant and took it for a test drive only to see it overheat every time.
I also Pressurized the Cooling System and it held 15 psi no problem.
I preformed a Engine Block Test and found NO exhaust gasses in the Coolant system.
No overly hard Coolant Hoses, Hoses goes soft after engine had cooled down.
No coolant Leaks No loss of Coolant whatsoever.
No Coolant in Engines Oil.
The engine runs as smooth as before the overheating issues.
I read on a different forum of a guy experiencing the same issues but never said exactly what the issue was, here’s the link below.
https://forums.mbclub.co.uk/threads/...e-high.210629/
Any help would be Awesum!
I have a 2009 Mercedes GL320 Bluetec with 230K miles.
I removed my Thermostat and at idle/normal driving around town my engine temperature stays around 95 deg Celsius, and ONLY when I’m going 70-80 MPH up a Large Hill on the Interstate my engine temp gauge quickly fluctuates between 90-120 deg Celsius.
My Coolant Temperature Gauge has NEVER NEVER NEVER ever went over 90 deg Celsius, in times past while even going up Steep Mountain’s at 85 mph, I know this true because i watch my Coolant temperature like a Hawk.
I have already replaced...
Water Pump.
Removed my Thermostat.
Replaced Coolant Temperature Sensor.
The Cooling Fan seems Normal runs Very Fast when temp goes over 100 deg Celsius.
And I’ve already considered a Air Pocket in the engines Cooling System, but I on 5 different occasions I pulled and held Vacuum on the Cooling system before refilling it with coolant and took it for a test drive only to see it overheat every time.
I also Pressurized the Cooling System and it held 15 psi no problem.
I preformed a Engine Block Test and found NO exhaust gasses in the Coolant system.
No overly hard Coolant Hoses, Hoses goes soft after engine had cooled down.
No coolant Leaks No loss of Coolant whatsoever.
No Coolant in Engines Oil.
The engine runs as smooth as before the overheating issues.
I read on a different forum of a guy experiencing the same issues but never said exactly what the issue was, here’s the link below.
https://forums.mbclub.co.uk/threads/...e-high.210629/
Any help would be Awesum!
Last edited by Aquinomas; May 3, 2021 at 12:47 AM.
Thread Starter
Newbie
Joined: May 2021
Posts: 6
Likes: 0
2009 GL320
My hypothesis.
Is that there is something wrong with Transmission that’s causing it to overheat.
or
Its a Electrical issue that’s sending false information.
I’ve considered a leaking head gasket, but other than the overheating there’s no evidence of a head gasket leak.
Is that there is something wrong with Transmission that’s causing it to overheat.
or
Its a Electrical issue that’s sending false information.
I’ve considered a leaking head gasket, but other than the overheating there’s no evidence of a head gasket leak.
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Thread Starter
Newbie
Joined: May 2021
Posts: 6
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2009 GL320
The water pump that was replaced seemed fine, and the new one checked out ok as well.
They looked identical.
I don’t know how to measure flow rate out if the Radiator.
They looked identical.
I don’t know how to measure flow rate out if the Radiator.
Last edited by Aquinomas; May 4, 2021 at 09:59 AM.
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Thread Starter
Newbie
Joined: May 2021
Posts: 6
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2009 GL320
The issue started after I tried pulling a 6,500LB Catamaran Style Boat.
And then I noticed the Coolant Temp rising for the very first time, I did not let it over heat or the car never warned me of overheating.
Now when I drive the MB it overheats unloaded when pushed a little hard.
And then I noticed the Coolant Temp rising for the very first time, I did not let it over heat or the car never warned me of overheating.
Now when I drive the MB it overheats unloaded when pushed a little hard.
Thread Starter
Newbie
Joined: May 2021
Posts: 6
Likes: 0
2009 GL320
Something doesn’t seem right with the Coolant Instrumental Gauge Reading, using Star 5 the readings doesn’t seem to match.
When the Dash reads 100 deg Celsius the Star 5 is reading 240+Fahrenheit, which is way to Hot.
And when the Dash reads 95 deg Celsius the Star 5 is reading the Transmission Fluid temp at around 175 Fahrenheit.
When I get home I’m going to do a Cranking Compression test using Star 5 and compare the numbers from Previous readings when done at 160K miles.
When the Dash reads 100 deg Celsius the Star 5 is reading 240+Fahrenheit, which is way to Hot.
And when the Dash reads 95 deg Celsius the Star 5 is reading the Transmission Fluid temp at around 175 Fahrenheit.
When I get home I’m going to do a Cranking Compression test using Star 5 and compare the numbers from Previous readings when done at 160K miles.
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Joined: Jun 2010
Posts: 2,762
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From: Emmett, ID, USA
2007 GL450
my money would be on the radiator (bbpoolside). Hook a garden hose to the bottom radiator hose, unhook the top, catch the outflow with a bucket and see what gunk comes out.
