kingjohn1027

Yesterday I cleaned and degreased my engine compartment in my 1983 240D with 202k miles. I also added some cleaner to the diesel tank. Everything cleaned up just fine. On the drive home (about 25 mile drive with about 5 miles remaining) my temp gauge started to climb. it got to 110C before it stabilized from the heat being turned on. Got it home and let it cool down. Radiator is full and clean, no leaks, water pump changed out last year, no oil in water or water in oil and no steam from the exhaust, all electrical connections are good, both hoses are hot. after an hour of cooling down, i let it high idle in the driveway for an hour or so. The temp stays around 90C. The normal temp it usually runs at is 80C. If i had her on the highway going around 70mph, the temp would usually raise to about 90C and stay there until i resumed lower speeds. The fan clutch checks out ok. so do the belts and hoses. So i am somewhat stumped on what the cause of the sudden overheat could be. I dont know of cleaning the engine compartment did something, or if the additive i put in the tank is causing it to run hot. Like i said before, the first twenty miles of the trip home, the temp was right where it should be. Any information or suggestions would be greatly appreciated! Thanks!

Jonathan

lkchris

Perhaps you "greased" your fan belts and they are slipping.

kingjohn1027

Thanks for your input! I ran the vehicle again to see if the same thing would happen. It did, but not to the extent. i let it high idle again for thirty minutes, stayed right at 80C. when i took it on the highway and got up to speed, the temp started to climb. I got off the highway, and the temp went down from around 95C to a little under 90C. I parked it and let it high idle some more and the temp climbed back up to a hair under 100C. I checked the oil cooler lines, they are hot, also checked the belts to make sure they were not greased from degreasing the engine yesterday. They all looked ok. However, prior to running the engine this morning and while it was cool, i was able to turn the fan with some effort. The pulley slipped on the belt. The belt tension seems ok though and there isnt excessive slack or wobble to the belt when running. If you soak down the belts really good with degreaser, can it cause the belt to stretch? Im starting to lean towards the thermostat being bad. Its been years since its been changed anyways. Im thinking about letting the car cool down, removing the thermostat, and letting the car run without the thermostat to make sure that is the issue. One other thought. The additive i added to the diesel tank is Diesel Kleen +Cetane Boost. I got a bottle large enough to treat up to 100 gallons. I read on the back that to double the cleaning, to add twice as much. so i did. around half the bottle to a full tank of diesel. in addition, i purchased a bottle of sea foam engine treatment. I added half the bottle to the crank case and the remainder to the diesel tank. I added this prior to the drive to my buddies house to degrease the engine. the engine temp was just fine then. I am curious if i have added too much and is causing the engine to run hotter and just having a hard time dissipating the heat. I added almost a quart of auto tranny fluid to my tractor the other year and made it run WAY too hot. i had to drain the tank and refill. Think its possible i could have done the same thing here just with different fluids? Thanks again for the help!

kingjohn1027

Update: So i removed the thermostat and drove the car for an hour. no overheat issue at all. Its 85F outside right now in oklahoma. Was driving up to 80mph. The highest temp was 90C while i was at high speeds on the highway. The temp would drop down to 80C in under a minute after exiting the highway. With that said, I am going to venture a guess that the thermostat was indeed the culprit in my case. I am going to order a new thermostat and do a good cooling system flush while I'm at it. Does anyone know what the normal operating temp of an 83 240D should be? While driving in the city or idling, it will read right at or around 80C. While at high speeds on the highway, 70mph or above, the temp will be around 90C. Is this normal or should i consider looking further into my cooling system?