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A few years ago my 617 was running a bit hotter then I felt comfortable with so I set out to find a cheap fix. I stumble on this diy, tried it and it works fantastic! It works so good in fact that Ive removed my auxiliary fan and main fan, I run my 617 without any fans at all. Removing the fans also freed up a ton of room for my intercooler and associated plumbing. Running with no fans may not be for every one but if your rig is running hotter then you'd like it to be give this diy a try, I think you'll be pleasantly surprised. The only down side is it takes longer to get your engine warmed up, but I don't mind that.
I love Dieselgiant's site, lots of good info, but I'd have to disagree with this one. I'm not sure how this worked for you, maybe elaborate specifically on what you modified?
The Benz cooling system works differently than most other cars. It is a 3 way bypass system rather than a simple - open/close type deal like you find on most.
The diagram speaks for itself, however operation is fairly simple. Coolant leaving the engine block will enter the thermostat/bypass housing. If the temperature is low, the thermostat is "open" (disc not seated against bypass line inlet) and will allow coolant to return right to the water pump. Note that the path to the radiator is also open, however, since water takes the path of least resistance it will not circulate through the radiator.
If the temperature is high, the thermostat will have CLOSED off the bypass line leading back to the water pump and instead force the coolant to enter the radiator. Thus, I fail to see how drilling holes in the thermostat will do anything constructive. If the thermostat is closing (disk seating against the bypass line face) fully, you already have 100% coolant flow through your radiator. If it doesn't close fully, that's a separate issue.
For those experiencing overheating, verify block temp with an IR thermometer. Keep in mind too cold just as bad as too hot. . I would first check to make sure you're using the proper Zerex 05 or equivalent phosphate-free coolant. If not, change it. Alot of crud in my system thanks to PO using the green coolant. Citrus flush while you're at it will remove scale from the block. Also make sure you are using a legit Behr 80C thermostat installed correctly, it will go in backwards and this will make a difference! A shop installed it backwards on a friends 300D.
I'm not an engineer, I really don't know what to tell you. All I can do is report my result, and with this modification my engine never gets over 90°c even when its 110°f outside climbing a steep grade or stuck in bumper to bumper traffic for hours. Once its warmed up it stays between 80°-90°. I'm not the only one that's experienced these result a few of my friends have also done it with the same results. Diesel giant obviously has much more experience with the engines then you or I, so I felt confident with trying this modification and it work just as advertised.
If your actually curious how it works buy a new thermostat on your way home from work today and test it out. It will should only take about a half hour to complete the whole job.
Benz,
Hope my reply didn't sound negative, just haven't heard of many overheating problems with these.
Just curious, was your engine in question swapped into another vehicle or in a Mercedes auto?
My 300SD seems to stick to 85 regardless of load or climate, guess I got lucky for now. Although I have noticed I can lower the temp in the winter in traffic by blasting the heater...guess they do not generate much heat at idle. I'm very interested to see how the temp of the 617 in my pickup fluctuates once I start driving it, given it only has electric pusher fans also doing double duty for the A/C....
I do! I wish I had pictures of all the gunk that i flushed out of the cooling passages of my donor engine..yuck. I'm certain it would have had issues..
Also watching your pump thread with interest, I've tuned the Bosch APE pumps but never our M series, i'd be interested in a bit more safe power for sure!
Thanks! I can't wait to start driving it. It took many hours with various sized brushes, lots of de-greaser, and the brass wire wheel haha! But imo just cause it's an old diesel doesn't mean it has to look it!
04-02-2015, 08:13 AM
