I always thought my car ran at the normal operating temperature, but now I am unsure. My temperature guage only goes beyond 80°C when I am stuck in traffic somewhere. Lately the guage has not been getting to 80°C at all until I drive the car for about a half an hour. After a half an hour is when I begin to get heat also. Is this normal for the type of weather that we have been having or do I need a new thermostat?

I think the car should warm up a lot quicker than a half hour, even in cold weather. I sounds a though your thermostat is stuck open or partilally open. Buy yor replacement here at parts shop and they will get it to you quick and it will be a quality part. The car shold warmup in 10 to 15 minutes. Operating at too low a temperature the engine may experience premature wear in the cylinder bores.
good luck.

__________________
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T

I believe that JDUB is right on the money with his assessment of the problem.

I never saw a thermostat fail in this way until I began driving MB's. I've seen it happen twice. The first one was so bad that I froze until I replaced the thermostat. It was so bad, I got no heat from the heater. American thermostat failures that I've seen were the opposite, they would NOT open.

JDUB is also on the money about premature engine wear. Replace the thermostat as soon as practical.

JDUB, is your 5.0 Mustang one of the late '85's with the roller cam? I bought one new in April '85. The ones made after Dec '84 had the roller cam and the Holley. The car was a great one. The engines turned out to be a little dirty, and they were forced to go to the injection in '86 before they had the injection sytem opened up to take advantage of the rest of the engine, it choked some of the horsepower. You may already know this, but the production date is stamped in the sheet metal at the top of the door jamb on the passenger side. If it was built after Dec. '84, you have a rare gem.

Good luck,

[Edited by LarryBible on 12-22-2000 at 06:08 AM]

Larry is right. Until recently American thermostats weren't made to fail open. This is of course a much safer way to go, than to have a thermostat fail closed and have your engine overheat to the point of wrecking it. Change your thermostat. It also might be a good time to change your coolant.

__________________
Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired

I forgot the obvious, but thankfully, 420SEL pointed it out. In an engine with aluminum components, you should be changing your antifreeze every two years. My 300E did not have this attention and I suffered severe corrosion problems. The corrosion actually made it into the combustion chamber. I had changed the antifreeze, but the previous owner had not.

I now have an increased awareness of the importance of this commonly overlooked preventive maintenance step.

Merry Christmas,

LARRY, MY 85 MUSTANG GT HAS THE H.O. 5.O WITH THE HOLLEY AND THE ROLLER CAM. MY CAR IS HAS 177,000 MILES AND IS 100% ORIGINAL. THE CAR WAS MADE PRETTY WELL, IT STILL HAS THE ORIGINAL CLUTCH THE ONLY THING REPLACED ON THE ENGINE WAS THE TIMING CHAIN AND WATER PUMP. THE TIMING CHAIN WAS REPLACED WHEN THE FRONT CRANKSHAFT SEAL DEVELOPED AN OIL LEAK. THE QUICK ACCELLERATION COMBINED WITH THE SMOOTH IDLE AND DRIVABILITY IS THE REASON IS STILL HAVE THE CAR.
THE CAR DOES LACK THE SOLID FEEL OF A MERCEDES BUILT AUTO.

__________________
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T

I have an 88 420SEL, and as a normal part of maintenance, I replaced the thermostat and had the engine flushed. Since then, instead of staying around 80 degress c, it is just under 100, and even on these cold Buffalo days, the oil pressure is dropping from 2.8 to about 1.5 at traffic lights. Should I be concernec, or did the flush clean things out to work better?

Doug,

I wouldn't worry about the oil pressure guage at idle. I'm pretty sure all Mercedes do this. As long as that needle spikes reight back up to 3 when you give it gas (usually by 1000rpm its up to 3 and will stay there. I'm not sure about the car running as hot as 100 though. I have recently changed my coolant (previous owner used a non-mercedes coolant) ad if anything they car is running cooler. I have been considering changing my thermostat too, just as preventative maintainance. How much did it cost to change yours? Did you do it yourself? I will try to have my changed by New Year's and I will email you with the results. I do think these cars are supposed to run just a hair about 80 degrees C. Did you get it done at a dealer? If not maybe they gave you a thermostat that opens too hot. If you can't wait for my answer give MBUSA or your local dealer a call. Ask to speak with a service advisor and see if that is acceptable engine temp.

I'll let you know how mine goes. Happy Holidays and Happy New Year

__________________
Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired

Had it done at a local shop, not a dealer, in comination with a flush, oil change, battery check, etc. They have been an extremely reliable shop, not at all like some I hae been reading of here in the posts.. The thermostat itself was $45, quite a shock, really. The temp used to crawl up to 80, but I had no interior heat problems. I think I will research it some more, as it does seem a bit warm in weather around 20 or 30 degrees. I'll be curious to see what happens to yours...

Tom16v, JDUM said it all. 1 thought, I have a 300E and I use a 195 degree F thermostat. Check it out. Happy Trails Beep Beep from Houston.

Donald
we don't need them high ones here in the south

I recently had a new head gasket replaced in my 1989 300E by a local shop. When I picked the car up the mechanic said he did something like blocking off part of the cooling system. Now it takes forever to reach anything near 80 degrees. Anyone have some thoughts on what he did and why? I've tried calling him but he is on vacation. Any help would be appreciated! Josie's Dad

I can't think of ANYTHING good to be achieved by blocking off part of the cooling during a head gasket replacement. I really hope he didn't block cooling passages with the gasket.

I'm can't see how blocking cooling anywhere would make your gauge react slower. A thermostat blocked open could let the coolant take longer to reach operating temperature, if at all. That's not a good idea either! It took a long time for our diesel to reach 85 this morning with a proper thermostat, but it was 0F outside! With an open thermostat we would still be waiting for heat.

Personally, I'm stumped! Perhaps he didn't do a good job of explaining what he did.

BCingU, Jim

Dear Dad,it would appear that if a portion of the cooling system was blocked off, the temperature would rise more rapid and perhaps obtain a higher degree! The only item that blocks off a portion of the cooling system is the thermostat. It's not a block off it's a valve. Most of us consider a thermostat as that which heats the coolant, True but consider while the coolant is being heated in the engine the remaining coolant is being cooled in the radiator. So it depends upon the season as to what the valve does. At the temperature rating of the valve(thermostat) it opens and musical chairs occurs and we change places. So you see as others have remarked, "blocking off" doesn't jiv. Happy Trails Beep Beep from 195 degree thermostat Houston.

Donald
a blocked off block head

Apparently I misunderstood my mechanic (the German accent). What I did find was my thermostat was stuck wide open, therefore taking forever to warm up! New thermostat no problem! My next project is changing out the motor mounts and tranny mount. The engine runs just a little rough at idle and in reading some of the past posts I looked at them and saw cracks on both!Hopefully this takes care of it!

Josie's Poppa, Those rascals, the mounts, are what stop the engine's and tranny's bad language from being transmitted into the frame. Most of us have had them replaced, well I have! Happy Trails Beep Beep from no vibs Houston.

Donald.
Smooth as a Baby's
you know.