legendaryML500

Hi all. I'm new to the site and seeking some help. My 02 ML500 overheated while driving, so seeing how the car has 130k miles on it, I figured its time to replace the thermostat, upper and lower rad hoses, heater hoses, and flush the cooling system while I was at it. Bled the air out the cooling system when refilling it. So the car drove nice for about 2 weeks and now the temp rises to the red zone and the electric fan sounds like a jet engine.

I've replaced the water pump and radiator, thinking there was lack of sufficient water flow circulating through the system and lack of air flow threw the radiator. "Burped" the air out nicely, again...

AND the temp is still climbing to 120*C....... The temp rises gradually to 120*C from normal range ~90*C if the A/C is on blast, or at highway speed above 55mph. But when I turn the heater on to max the temp will quickly fall back down to ~90*C.

It seems to me as if the engine heat is not dissipating fast enough......... Any thought or suggestions is appreciated...

thanks

legendaryML500

Well here it goes. After $1200 later and a massive headache, the problem has been resolved. Come to find out the new thermostat I put in crapped out and was stuck closed this whole time. I did a thermostat test in boiling hot water after I pulled it out and saw that it didn't even budged. Got a new 87*C thermostat from the local NAPA store in exchange for the old one. Finalllllyyy it's done and over with!!!! Oh yeah, now that the engine temp is sitting happily at ~90*C, the car doesn't sound like an airplane any more... lolz

Well something good came out of this project. I found out that the water pump was ready to let go me. I can hear the bearings starting to grind a little while spinning the pulley (thank god I found that problem sooner than later).... Hope this can help others that's having a similar experience...

scutarius

LegendaryML500. I am having the same issue. Will you tell me where the thermostat is on the MLs?

art_arev

Trace the upper radiator hose to the engine. You will see the housing to which the hose is fitted. Thermostat is inside the housing.

scutarius

Thank you. got it