Long Commute

[Squiggle Dog]

You can splice a shutoff valve where the servo goes (look at the picture below of my last 300SD, you can just make out the blue knob of the valve, which is the type you can get at a hardware or plumbing supply store).


One time on 2,000 mile trip in my 1968 W110 200D, with my heater stuck on, things suddenly got very hot when traveling from 50 degree Washington into 90 degree Utah weather, so I had to find a hardware store and find a way to shut off the flow to the heater core. I used a C-clamp with metal and rubber fender washers, which actually worked the entire trip.


In my current 300SD, I removed the pipes on the firewall going to the servo, cut one of them up to make an elbow, then spliced in a shutoff valve that fits R/W107 and W116s with manual heat. It was about $30 from the dealer, part number 107 830 05 84. It works great, but I haven't hooked up the vacuum line for the diaphragm yet, so I have to open the hood to open or shut it off manually. Thankfully, here in Phoenix, I only have to turn it on for maybe one week in the winter, or if I drive up north.

[JasonP]

Thank you, Squiggle. I will study this some more, I cannot say I completely understand how it all works yet. I always thought that stopping flow to the heater coils inside the dash would cause the engine to overheat, or create a blockage in coolant flow which would damage the engine.

So as I understand your post, you showed me three different systems, or ways to shut it off, the first being a valve at the servo, the second being just a clamp for emergency use, and the third a more long-term solution whereby you removed the copper pipes themselves.

I would elect for the first system, as I want to eventually restore the original ACC system.

[JasonP]

Well, the boys at the tire place did a great job this morning. No more vibration at high speeds, no more rattle from the steering wheel. The steering feels tighter as well. They did a rotation, balance, and alignment, and there were no "surprises." 

[Squiggle Dog]

Shutting off the coolant flow to the heater core will not harm the engine in any way. You only need to shut off the hose that goes from the driver side of the block to the firewall. On cars with automatic climate control, the hose goes from the driver side of the block, to a pipe which goes to the passenger side of the firewall to the servo, then it goes through a pipe which goes back to the driver side and into the firewall.

So, putting in a temporary valve anywhere in this line should work (such as removing the hoses from the servo and putting a valve in its place). Just don't put it in the hose that goes from the water pump to the passenger side of the firewall. The water pump pushes coolant through the block and if the heater valve is open, the coolant flows up through the driver side of the heater core, through the heater core, then out the passenger side, and back to the water pump.

Putting the valve on the passenger side of the vehicle would cause warm coolant to get into the heater core, while putting it on the driver side of the vehicle would prevent the warm coolant from getting into it.

It's good to hear that the tire shop was successful. I'm starting to get squeaking and clunking noises from under my car, which makes me wonder if I have a blown shock absorber or something. I'll have to check it out.

[JasonP]

So, Mr. Squiggle, and others here, I want to attempt this valve installation this weekend. Here you see a picture of my coolant hose going from my engine block into the firewall. If I am not mistaken, this is where I would like to place the manual valve to start and stop the flow of coolant to my dash.

Now, what exactly should I purchase to get the job done? The hose looks like it is in pretty good shape, and I do have spares from my parts car. I guess I just need a valve and two clamps for either side?

Any suggestions? Be as detailed as you want, please. 
   

[Squiggle Dog]

Here is what I did (but you will not be able to reuse your old hoses or firewall pipes). I didn't care because I am going to convert to a manual system at some point. I cut down the hose that actually comes out of the driver side of the firewall enough so that I would just have enough room to put on a hose clamp and still be able to tighten it. I then put the valve on the end. The firewall pad actually has a portion that can be removed, with screw holes underneath for attaching the valve. I put spacers in there because the proper way to attach the valve is to have it stick through the firewall and attach it underneath the cowl where the wiper motor is, but I didn't bother to do that since I needed a quick fix until I did the full manual conversion.

I reattached the end of the firewall hose that I cut off to the end of the valve. I completely removed the two pipes on the firewall and cut the elbow off of one to make it bend to reach the hose going to the engine block, which I also had to cut down.

The picture I attached is pretty straight-forward. All I needed for the partial conversion was the new $30 valve (107 830 05 84), a vacuum cap to keep junk out of the open end of the valve diaphragm, a couple screws, a couple spacers, and a small pipe cutter/cutting disc to cut down one of the pipes. And maybe a few extra hose clamps.


With that said, if you plan to go back to the automatic climate control, this may be too drastic if you want to eventually restore the system. I think that in that case, disconnecting the coolant hoses from the servo (which has two passages), putting a straight pipe or flush tee where one of the servo passages was, and then a valve in the other will be simpler and easier to go back to original. You can use the $30 valve from Mercedes-Benz, or just go to a plumbing/hardware store and get a shut-off valve, with a fitting on each end that that hoses will slide onto.

So, for the easier of the two ways, I'd remove your servo, and replace it with a straight pipe of the correct diameter and length on one of the connections, and put in a plumbing-type shut-off valve and add fittings on each end that the hoses will fit over. If you are really creative, you might even be able to find a shut-off valve from another make of car and run a cable in through the firewall so you don't have to open the hood.

If you have a wrecking yard nearby with imports, you could take in your hose (the yard attendant will probably mark it) and then match it up to a coolant shut-off valve from some other car, and get the cable with it. Basically, you could make a kit like what Kent Bergsma is selling, but for less money and made from used parts. Maybe I should find out what cars have compatible parts, look for them in the wrecking yards, and sell my own manual heat override kit.

[JasonP]

Maybe I should find out what cars have compatible parts, look for them in the wrecking yards, and sell my own manual heat override kit.

Let me be your first customer.

I don't understand why I can't just stick a manual valve next to the block side, instead of the servo side?

I'll attempt that servo side, hopefully this weekend. Thanks, as always.

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Today on the way home I took the interstate, so I could go through town and get stuff on the way home. Three trucks, going 70+, we're in the right-hand lane, and I had to reach my exit in 1 mile. I had no choice but to pass those fuckers. I hit 85 for about 45 sec. to 1 minute to get past them, and made my exit. The car did great. I heard a funny harmonic a little bit later, at a stop light, but as I started to listen to my engine, another car drove past with a really bad engine, so I could not hear mine. I got mad, but then felt bad for the person with the worse car! Smooth ride home, no noise, no problem.

I wonder what it looks like to see a 34 year-old Mercedes doing 85 mph on the interstate, with a totally cool, handsome guy driving. 

[Squiggle Dog]

I don't understand why I can't just stick a manual valve next to the block side, instead of the servo side?

You probably could, but you'd have to cut the hose coming off of the block to put it in, and then you'd have to see if there is clearance from the throttle rod, injectors, and engine.

I've had a few times where the traffic in the right three lanes is going incredibly slow, so I've moved into the fast lane. Traffic would come up fast from behind, so I'd have to get up to at least 85 miles per hour so they wouldn't run into the back of me. I'd just hold it there until I could move over for them to pass. I could drive faster, but those are ridiculous speeds on a freeway when you consider how much time it takes to stop a car.

[JasonP]

Well, summer is over, so no more need for AC. I survived. Perhaps next summer I can restore it. Thank MB for the sunroof!

I did have a question for all of yous on RPMs. I run between 3,000 and 3,500 RPMs on the highway, for about 45 minutes at a time, which translates to a speed of 60-70mph.

What do you guys think about that for an old diesel engine? Is that too much? It has about 265,000 miles on the odometer. Runs nice, no knocking or anything, only smokes on sloppy start-ups (the glow plugs need to be maintenanced).

Just wanted your expert opinions.