I'm sure that most pump bodies can accept the new primer pump with no issue but Bosch seems to acknowledge that it might not so they give you a precaution. No reason not to properly use a little high-quality sealant.

Glad that yours are working out well.

Dan

Just because Rectalseal is used in spacecrafts does not automatically warrant it's use in an injection pump system.

I don't recall anywhere in the FSM where a threaded fuel fitting sealed by a copper or aluminum washer calls for pipe dope sealant. I don't understand why Bosch would make an exception in the lift pump. Can you post a copy of the instructions?

No matter how careful you are in applying the pipe dope, the concern is during subsequent R&R where the dope will be disturbed and fall in. The lift pump is not in a very accessible location for cleaning. How do you plan to clean it out? Take the lift pump off? That is more work than I'd want to do.

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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

The mating surfaces of the crush washer on the lift pump is just as good today as it was 30 years ago, provided it is not damaged by improper installation.

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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

For those who haven't read whole thread, it was mentioned in post #7 by Rebe that instructions that came with pump recommended use of Loctite 638. I Googled that and provided a link. So yes, Bosch does suggest using sealant.

In my case, original pump leaked, so did second brand new Bosch pump. When new slightly off-size crush washer was installed using same pump still leaked. Installed second new pump, but this time using sealant on crush washer surfaces as well as top few threads. I said silicone earlier, but I actually used this Permatex product.

It's all very well to write all these motherhood statements about sealants. Most of us know that stuff and have heard it over an over. But in the end, you do what you have to do with these old cars. I have been without a fuel leak for what must be a couple of years now - because I used sealant!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

What is this "threaded bush and gasket"? Do you have a pic? Is this for your 83 240D? I replaced the primer pump in my 83 240D years ago and as I recall all that was needed was the primer pump and a new (supplied) copper crush washer.

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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

They come with a reducing adapter so that they can fit two sizes of female thread.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

What year and model lift pumps need a reducing bushing in order to fit the updated primer pump? I'd think the sealant is recommended by Bosch only between the bushing and the primer pump since it is not a self sealing pipe thread. Once the sealnt is applied, it is permanent and the bushing would never have to be undone again so FOD is not an issue there. The seal between the primer pump/bushing to the lift pump would then be just the copper washer, no sealant.

You said the dealer gave you a copper washer that is too large which you were able to seal with the addition of sealant. Maybe if you had the correct washer, it would have sealed by itself without the need of sealant? I think sealant of any type is a bad idea anywhere in a diesel fuel injection system. I do not recall anywhere in the diesel fuel injection section of the FSM calling for it. But if nothing else works.........drastic measure is a last resort.

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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

Those priming pumps are used on all sorts of diesel engines. Even trucks. Some of them must require a different thread size.

I think you misread my post:
-Brand new Bosch pump with new crush washer leaked.
-Same pump with slightly oversize new crush washer also leaked.
-Same pump and oversize washer with sealant still leaked.
-Second new Bosch pump and new washer with sealant does not leak.

Sometimes you just have to do what you have to do after the motherhood methods fail

The best primer pump it seems is the Monarch pump. Probably wouldn't overcome the leak problem, but sure looks like a nice unit. My dealer also had a pump - identical to current Bosch pump but a little more pricey!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Mine leaks with it unscrewed. I go with the method of not touching it. I'm a redneck and just crack the injector lines and crank the hell out of it.

I'm gonna order that monark one eventually though. It's like $20 if I remember correctly. Looks legit.