mrathell

My 2009 GL450 threw the code yesterday.

I cleared the code today, it's about 11 degrees F outside and I took it out for a short drive,

The temp reached about 70 degrees in under 5 minutes of driving and then I parked and let it sit idle for about 5 minutes. While siting idle the temp stayed constant at about 70 degrees. Next I started driving again and the temperature quickly rose to just under 80 degrees and stayed at about 78 degrees all the home.

My questions is......Based on my results today do you think those are the temps to be expected under each scenario? Is 80 degrees F the normal temp?

I'm wondering if the P0128 was just an anomaly.

Either way it looks like a very easy job to replace the thermostat.

DennisG01

Sounds more like celsius than fahrenheit. If it is F, then no, it's nowhere near normal.

mrathell

Ha, yes it should read Celsius. The owners manual only mentions the temp range on very heavy use but doesn't state the the normal operating range.

Does anyone know the normal operating range?

gl450x164

mrathell

Thanks. I picked up a new thermostat today and installed it in about an hour.

alx

this. they do fail open.

Kulle

do you recall if you lost a lot of coolant and what the steps are you took? i have an ml350 and assume steps are similar.

thanks

mrathell

I didn't loose a drop of coolant. Mine was stuck in the open position.

Here is a link to a YouTube of the removal/install. It's not on the GL model but perfect for your ML.

GL owners don't expect to have no where near the working room as in the video. On our GL's it's a tight fit to work in.

There is no need to drain the coolant. Only about 3 cups of coolant will be lost during this procedure.

There is no need to remove the fan housing our any other parts to try to gain add'l room, it would just be more work than it's worth.

From start to finish it should take you about an hour.

- Remove the serpentine belt.
- Remove the idle pulley (the one blocking one of the bolts on the thermostat housing).
- disconnect hose from Thermostat housing.
- unplug the plug from the thermostat housing
- Remove the two bolts from the hemostat housing
- now you can take the thermostat housing off the engine.
- remove old gasket and gasket remnants
- install in reverse.
**Use blue locktite on the bolt threads when reassembling.
- Top off coolant (only use distilled water)

-

GLguy

Did it this weekend. Pretty much followed the steps. But, I also removed the shield on top of the radiator to get extra room. And, I did not use locktite since the manual does not call for it and there were no traces of it on bolts.

mrathell