'82 300SD overheats in 114 deg. stop and go traffic

I have the same issue on a 1984 300D Turbo, not as extreme, it was happening to me on a 95 degree day in stop and go traffic. I will be following this thread closely for possible solutions.

Perhaps your auxiliary water pump is dead and creating coolant blockage as the part listing on this site describes... See it here: [http://mercedessource.com/node/6001]. Hope that helps, good luck!

BioDrew,

I know that I had problems with heater function while in stop and go traffic this last winter around home. I did not think of it while I was in the Vegas heat but now that you mention it that does sound like a contributor to the problem. I have purchased a new pump and just found out that it has shipped and is on its way. I can’t wait to put it in. Thanks for your input.

Mark

I replaced my auxiliary water pump 2 yeras ago as a preventative measure - hard to believe it would have gone bad. I should have kept the old one so I could test. This site says that the pump will effect heat output in the winter. I am not sure a blockage to the heater core could have an effect on the overall operating temperature, I guess that depends if water must be routed through the entire system, or is the heater core a seperate branch. Comments are alsways appreciated.

Well over the weekend I replaced the engine water pump as well as the heater recirculation pump. After starting the engine it took a while to get to operating temperature but when it did I notice that the heater hose on the injection side was hot but the one on the exhaust side was still cool. In fact none of the hoses on the firewall were hot. It turned out to be just an air pocket because after running the engine at around 1500rpm with the heater turned to max all hoses along the firewall became hot. Once the air was out of all the lines, I continued to allow it to just run at idle. After about 15 minutes of idling I could notice rpm changes of the engine cooling fan, confirming the fan clutch was performing correctly and also noticed that the aux. fan was cycling on and off. Ambient temp was 89F 50%RH. This I feel is how the complete engine cooling system is supposed to function.

I feel that maybe a non working heater recirculation pump, even though it might not have a significant effect on engine cooling normally, might create enough blockage in the heater circuit that very little water is allowed to circulate from the backside of the engine and during extremely hot ambient temps it could cause the excessive rise in engine temp that I experience in Vegas.

I also want to note that after removing the old engine water pump, installed some time ago by the previous owner, I compared it with my new one. I compared impeller design as well as dimensions between the two and the differences were very noticeable. The old unit had no brand recognition either and I suspect an inferior brand of cheap manufacture. The new unit purchased from Mercedes Source is a Meyle brand and appears to be of superior quality and impeller design to the old unit. This in itself may have a significant effect on engine cooling during extreme conditions as well.

I have a trip planed later this month to Laughlin and hope to experience some high temps once again but this time I feel better prepared. I will add my comments once I return.

Thanks to all for your input and thanks to Kent, his crew and to Mercedes Source for great products, a place to learn and teach, and for the outstanding service.

Mark.

If one is not concerned about not having enough heat is it possible to bypass the heater circulating pump without affecting the radiator's ability to cool the engine? I think mine was bypassed last year when it started leaking and I balked at spending the money to replace it on the advice it was auxillary anyway. Not enough engine heat is a rare problem in San Antonio.

On a recent trip via I-40 to CA where ambiant temps were 100+ the temp gauge was higher than I had ever seen it before as I was clipping along at the posted 80 and going up long mountain passes. I'm wondering if that is normal considering the conditions or should I be concerned? It went back down to normal operating temps when I slowed down to 60-70 mph. What should I be asking my mechanic to check? Thanks!

Ever since my long road trip I've noticed the temp running hotter than normal particularly when then AC is running. Now its been 100 degrees lately but it almost redlined on the highway the other day. I noticed there is pressure and exhaust smell when I open the radiator cap after a few minutes when I start it up. I fear this is a sign of a blown head gasket. I got a quote of $1700 to repair that. Figuring I had nothing to lose I added a bottle of Bars head gasket repair to the radiator but have seen no improvement. Is there anything else I can try that will at least buy me some time?