Mercedes-Benz Forum banner

Coolant change = higher temp?

1641 Views 16 Replies 6 Participants Last post by  300se126
OK, feeling a little bit like an idiot here. Changed the two radiator hoses and the coolant last week and now have higher temp at idle and a slower cool down time while cruising. Used Pentosin coolant right at 50/50 but have noticed that while cruising temp is normal, right at 80c, at a stop the temp climbs rather quickly to right at 100 c and then when I take off it goes slowly back to 80c. Fans come on fine but I want to know what I did wrong with the coolant change to cause this because before old knucklehead (me) got his mitts on it it was fine, usually rock steady at 80c. Can air get trapped in this system and cause this? I let it run without the rad cap long enough after the thermostat opened but I wonder now. Any ideas? With hot Sacramento summer temps coming soon don't want to let the old girl get hot.
1 - 4 of 17 Posts
jhodg5ck said:
I like Pentosin oil but I know nothing of their coolant..
It's great. I've been using it in my Audi for years. It's the only coolant most Audi tuners and shops use, as it really does a nice job of keeping the engine free from deposits. Plus, it's red, so it looks cool!
cjscopp said:
300se126- the Pentosin I got is blue. You got it in red? What, do they offer designer colors???LOL BTW I like your 250,000 km badge, I have one on mine too.
You have G11 coolant; the Audi juice is G12. As for the badge, it stays firmly put on my desk where it won't get stolen or crudded up with dead bugs. I need a new grille surround soon, as the old one is tarnished, and I was thinking about doing a custom install of the High Mile award in place of the stock Mercedes emblem - yet keeping the hoodstar of course! The award looks so close to the stock emblem, I think it would be cool.


See less See more
Maybe the temp sending unit is shot? I hate to say it, but I needed to unclog my radiator when this happened. It never got perfect, and I'm putting in a new one soon. Also, try drilling a 1/8" hole in your thermostat - it really helps - and make sure you don't leave any shards of metal loose in there when you are done! I filied my thermo-hole mod with a small round metal file when done and then rinsed it thoroughly with alcohol, then distilled water.
KAZ_300SE said:
I finally came to changing radiator and it worked.
Me too. I found a lot of "leak-stopper" in the core. They should call that stuff something more appropriate, like "instant death" or "cooling system ruination solvent." Grr. I de-crudded the monovalve assembly with a toothbrush for good measure while I was at it, since the crud particles do like to amass in there. The thing hasn't crossed the 87-degree mark since. Hooray!
1 - 4 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.