You forgot about the exhaust manifold and the turbo, which is under the inlet manifold. Heat rises and you have the pump mounted at the highest point in the engine compartment above the hottest components. There are much better spots, like next to the aux water pump, away from the heat of the turbo.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

What Turbo ? No turbo in a OM617.912 engine.


Heat does rise, but I cannot see how in the world that much heat will transfer from parts A (anything which radiates heat) to part B (pump). I guess the real test is to drive it around a bunch tomorrow and get the thermogun out. I am betting 125F would be the max on the worst of a S.C. day in mid-August. Better yet, having opened the hood in the dog days of Columbia, S.C. heat after driving around a lot, I know for a fact that once I opened the hood, there was no 100+F heat wave from the engine. If I can touch a part immediately next to the pump with my hands, I have a hard time imagining that temp is 150F or more. Since there is around 4" of air space from the hottest thing possible (exhaust manifold), not sure radianting heat not in a direct line of sight so to speak could heat up the pump to 150F.

After your first post, I drove the car around to operating temp. I can hold my hand about 1" from the exhaust manifold and there's no heat wave so to speak--not even close. However, as I said, I will get the thermogun out tomorrow. Might be a good catch.

The temp gun is the great equalizer, however.

Temp Gun: 98F.

Current ambient Temp: 78F

Drove it around for about 45 minutes. All conditions, highway, suburban, sitting in traffic on Clemson Road. Engine temps are at their max as for any given day. So, Mr. Funola was correct in that the pump does pick up some radiant heat off the engine, however, no where near the 150F.

HOWEVER, I think this is a GREAT catch by Mr. Funola. I will get the Thermo-Tec matt and cover the bottom and both sides. A 12x12 section is around $12 bucks shipped. Any heat blocked is a good thing.

I gave up on the W126 pump. There's no way around the built-in electronics of the blow-suck cycles. So, I opted for the original pump I tinkered with a while ago. It's from an Audie. I hate using non-MB parts, even for a mod. It's close enough ... German made. Runs nice. I am going to run 2 lines off the vacuum port: one "T-ing" into the resevoir in the back and one line running up to the front of the engine into a 4 way deal. I will remove all vacuum lines from the engine bay (except the one to the IP) and have them tucked inside under the dash. The W126 pump is for sale.

I am totally SHOCKED it fits just about perfectly in the foam rubber housing. I also found a good use for the thick neoprene jackets from the cone filter I just removed. Two of them fit around the head of the pump perfectly. I like the way it fits the head in one end of the foam housing and open space for the other end, with the hose outlet and wiring fitting where the MB part went. Normally, mods are a PITA sometimes. This will get rid of my mechanical vacuum pump. Since I am going with manual brakes, I only need minimum vacuum and I don't need it 100% of the time. This clears out some needed space in front of the engine and clears the way for the serp belt set up I got cooking. I already tried the machined plate for around an hour with no booster and I am likewise surprised ... so I am guessing once I mod the ratio to 5:1, it might stop better than vacuum assisted. No way for the flagship 6:1 ratio.

Now, I am looking for a decent vacuum shut-off switch. Anyone out there run a 12V switch they like ?

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Don't forget the pump itself also generates heat so you have to add that to the engine heat. Instead of insulating it, why not relocate it to a lower elevation? Where you have it is the worst possible place. Pumps should be placed lower than the outlets anyway to avoid siphon action..

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I bought one from Jegs, and I have the same pump as you. I'm not too happy with it, as it likes to stick in the off position from time to time, shutting off the pump. So, I ran a wire from the brake light switch to a switch on the dash to the relay, so the pump comes on as soon as you step on the brake pedal. The switch in the dash is to override this when sitting for extended periods on time, like at a stop light, etc. I'd post pics but apparently I'm too much of a noob.

On a side note: add a check valve into the line between the pump and the vacuum switch, as the pump will NOT hold vacuum!

Very unlikey conclusion as you comment based upon the facts thus far. Without insulation, I gained 20F. There's many "worst" places, such as inside the cabin where it hits 130F during the summer with the windows rolled up. The trunk is pretty close. But, I see a ton of folks who really tinker with the M+W stuff and they have trunk mounted kits. I could mount the pump on the roof and I bet it would hit 115F+ in the summer. So, that leaves the engine bay. Even assuming I could mount it down by the bumper or the farthest possible area from "any" heat source, does 20F make a difference? I doubt it. With insulation, I am betting that will solve 10F even though the product I am getting claims up to 90% of radiant heat is blocked. So, will 10F or even 20F make a difference? I doubt it. How much heat the pump generates will be tested. Who knows, maybe your guess work is correct. As for my real engine, the 115 longrunner intake won't work with the current plate mounted application, so I am hunting for a new spot in 2015. As for the pumps specs, I could mount that pump underneath the car or the roof and I would only be getting to around 1/4th of the pump's draw specs. Currently, it's around 10", which is 1/8th of the pump's specs. I do appreciate the comments, and the insulation never crossed my mind, but the other stuff you commetned on a few times fails any real test or real measurement.

Thanks for insight, but I am getting rid of my vacuum boosted brakes and going with manual. I have machined plates for the current ratio which is 4+:1. I have a plate for 6:1 on the nose, but it won't work. I can do 5:1, so I am working on that plate now as well as a mod'd brake pedal arm.

Right now, I did a trial run with the OEM spec ratio but without the vaccum booster. I was pleasantly surprised. I can say it was actually better braking than my prior MB W123. I think the 5:1 ratio will actually out perform the current vacuum boosted brakes. So, I only need a little vaccum, e.g., 4 door pods, trunk and fuel lock, IP, ignition, and HVAC pod (I have manual HVAC controls).

Do you recall what you set your vacuum at ? I think a lot of those switches are adjustable. I will have a light bulb in my cluster which will go on when the pump is running and I will have have a on-off switch to kill the pump if the pump runs more than 15 seconds for example. If you remember, please let me know.

I set it to 20", and played around with it to see what works best, and went back to 20". Anything less and the brakes didn't feel right. But since you don't have a booster you may not need as much. I also bought a vacuum pod through my work (Oreilly's) to hold a little reserve for the shutoff switch. Everything works great, except I think I have a small vacuum leak in the hvac control unit, as it'll lose vacuum if it's in the "off" position, but won't if it's on heat, a/c, defrost, etc.
I'm also running a separate pump for the transmission, a cruise control pump off of a '99 or so Ford Super Duty, which is doing that job nicely and doesn't seem to care that it has to run all the time.

For the solenoid to shuttoff I ran one from an old climate control cluster. Any EGR solenoid form a modern car will work as well. Ford's definitely will work.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

I'd love to eliminate power brakes entirely and I'm very interested in your progress on this. Please post some pictures of your setup when you can.

If you want a well made adjustable vacuum switch ask this company for a free sample of # 21474 Vacuum Switches PSF109S DesignFlex | High Current, Adjustable Set Point, Controllable Hysteresis :: psf109s vacuum switch series I asked for a free sample using their form and I received one in a little over a week. I didn't get any reply or confirmation - it just showed up. It's a nice switch with about about 3"Hg of hysteresis so it won't cycle frequently. Adjustment is made through the vacuum port and it performed per specifications.

I got one to use on my W115 electric vacuum pump conversion. I have the aluminum booster and master cylinder from the W201 and a new Continental pump designed for stand alone power brake use. I haven't found the time to install it yet and if I can get away with manual brakes I'd do it without hesitation!

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1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

I'd think you could source a smaller diameter master cylinder and do it that way.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You'll need more room for the same braking force, though.

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

So, Mark, I guess that's my question: how are you compensating for the fact that a higher pedal ratio or a narrower MC will result in an increased brake pedal travel? Is the max pedal travel not utilized under the current power braking system? Are you raising the height of the pedal? Making a hole in the floor ?

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Smaller mc will increase line pressure with the same poundage applied to the pedal. Same force, smaller area receiving It gives the mc more leverage on the same wheel caliper piston.

Or increasing the size of the caliper piston will work as well.

I have increased the caliper on my 115 benz with excellent results. I also did it with my old 71 bronco with excellent results. More power on the brakes with the same or less pushing.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.