This weekend I drained the radiator of old fluid,poured a couple of gallons of water thru it while it wasn't running until it came out clean,then re-filled using 50/50 mix of green anti-freeze.Now when driving the temperature guage jumps from below 80 to 90-but never goes higher than that.It won't stay in one position anymore;before it was rock-steady at 90 after warm-up.After reading the posts,some guys say don't use green fluid-others say it's ok.Any thoughts on why this is happening?By the way-the old stuff seemed to be a mixture of green and orange.....

You probably have some air trapped in the cooling system that causes the temperature sensor to jump around. Purging all the air can take a while, so keep an eye on the level.

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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

You might have air in your system.....Watch your reservoir and you might have to add coolant...I don't think that the color will matter and today's antifreeze is made for aluminum.....other's swear by MB antifreeze but if you go to some dealer's, you will find them using other than MB antifreeze....you probably have air in the system..most of the time the air will work its way up to the reservoir..Some systems need to be burped....Jim

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James A. Harris

Thanks!I just went out and checked the level-it was still full.I ran it for about 5 minutes with the heater on and the cap off-didn't see any bubbles.It was still a little warm from driving to work.BTW-I don't have a reservoir-just a line going to the ground.Is this right?

von sponyiak

It might help if you told us what engine you have.
the best way I have found to purge the system is have the front end of the car raised up, disconnect heater hose (head to fire wall) at the fire wall, (wire the end up) pour coolant in through upper radiator hose till it comes out the heater hose. That works even after I have had an engine (616 or 7) completely drained.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Sorry about the engine!I have a 1982 240d.I'm trying as we speak to add my car to my name.....

I also have a 240D, mine is an 80 but I believe its the same cooling system wise. There is a bolt in the top of the thermostat housing that when removed while running and filling will allow you to get most of the air out. As soon as your antifreeze mixture begins to come out replace the bolt and check to make sure the radiator is topped off before replacing the radiator cap. After driving for a day or two I'd check it again and top it off one more time. Good luck!

Thanks!I will try the t-stat bolt tonight and let you know how it turned out

Just wanted to let you know that i used the t-stat bolt to let the air out-guage reads fine again! Thanks again for the help!