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Registered 2005 SLK350
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47 Posts
Discussion Starter #1
When I bought my car some time ago, I changed the stat for an after market one which is ok but I'm OCD about engine cooling and occasionally the stat would stick and the coolant would run at 80 celcius.
I dug out the original stat from the scrap box in my garage and cleaned it, first thing I noticed was a part number with a M-B sign followed by the part no. A272.200.00.15, underneath was cast WAHLER Germany.
I had wondered what the electric connection was at the side of the casting, it looks very much as though it's a heater element for the wax capsule, can't wonder why it's there though.
So a wahler stat was ordered up and fitted to the head, don't forget to connect up that little electric plug.
When every thing is back together fill the cooling system completely so the vent pipe from the thermostat outlet is submerged and squeeze the pipe enthusiastically, air will vent first up and you'll need to keep topping up the header tank as the air is displaced. You'll eventually come to a point where air ceases to be displaced and the pipe takes on a more solid feel.
At this point I used a syringe to reduce the amount of antifreeze in the header tank and, with the cap off the header tank started the engine, leaving it run for a few minutes whilst I watched the level in the header tank, which didn't need topping up.
When the temperature climbed to about 60 celcius I stopped the engine and pressed the rest button on the aircon, for those who have read the manual you'll know that this starts the circulating pump up in front of the header tank.
I left it about 10 minutes at which time there was a big bubbling sound and the tank level dropped about 1/2".
The level was still slightly above the bar so I took it out for a run and the temperature settled at 95 celcius.
At one point on the run the temperature went up to 105 celcius so I went home and I've left it in a nose up attitude for 30 minutes or so merc temp gauge.JPG
Put about 50 cc of antifreeze in and took it round my "circuit" about 23 miles and stopped for fuel where I took the picture, hopefully showing the temperature at 95 celcius, where it had stayed, rock solid, for all the time I was driving.
Job's a good un, now to book it in for MOT.
 

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Registered 2005 SLK350
Joined
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47 Posts
Discussion Starter #2
Just to square this one off, had to top up the cooling system, about 40 cc of 50/50 and expect to do this a few times more as all the air pockets are eliminated.
One benefit I hoped for has come in spades, my "circuit" normally returns 23.8 mpg on the computer a mixture of hard and soft driving, today it's showing 28.5 mpg which was better than I hoped but time will tell.
 

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Registered 2005 SLK350
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85 Posts
Thanks for the write-up, almost same as I did with same results. The one thing that I did puzzle over - How does MB do this, they certainly wouldn't spend the time that we did. I am still wondering.
Safe driving guys
 

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Registered 2005 SLK350
Joined
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47 Posts
Discussion Starter #4
Bob, my understanding is they use a vacuum pump to fill the system from the bottom up. As I have a small vacuum pump, the thought actually crossed my mind but before I expended significant time on making up adapters etc I thought I'd try the old fashioned way.
 

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Registered 2005 SLK350
Joined
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85 Posts
That sounds sensible, may be worth getting a system made. I could use it on the Disco but LR do give us a breather right on top of engine which has helped although messy. Anyway I enjoy making up little systems - had fun with the auto box pump and level check unit. That was really useful for the SLK and Disco.
Stay safe.
 
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