I tried doing a search but didn't find what I need:

I'm getting ready to fire up the 617 ('85 300SD) in the S-10. I found a couple of my mistakes that I'll fix tomorrow but I also found that the primer pump leaks when priming. It seems fine when I tighten it back down and it does seem to pump fuel when I'm activating it. Is the leak normal or should I replace the little devil? Mine has the white plastic top (handle?) on the pump.

Thanks

Dan

It shouldn't leak. You should replace with a metal Bosch pump - I bought mine off eBay from a truck supply vendor for about $10.00. You need to clean up threads and make sure old crush washer is removed. They tend to leak around mounting threads even when new. Hard to keep free of fuel when installing, but that is what I did and used some RTV thread sealant.

http://www.ebay.com/bhp/diesel-primer-pump

http://www.pelicanparts.com/catalog/SuperCat/3306/MBZ_3306_FULINJ_pg1.htm#item3

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

edit - didn't read your post correctly

Yes you need a new pump...

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I did this over a decade ago. My how time flies! Here's my payback! Diesel Primer Pump Replacement

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Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic

Thanks for the input, guys. New pump is on order from Pelican.

Dan

It shouldn't leak while pumping, but if it doesn't leak while tighten down, it shouldn't prevent you from starting the engine.

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1983 123.133 California
- GreaseCar Veg System

I purchased a new bosch primer pump. I haven't installed it yet waiting until I get parts for transmission and put together first. I was reading on it and it says to clean and degrease M22x1. Screw togehter hand pump threaded bush and gasket by hand. Coat thread M22x1 of threaded bush with Loctite 638. Screw wnit comprising items into pump housing and tighten to M 37 +or-3 Nm. If you don't need the bushing, I was wondering if you still need to use the 638 Locktite on the threads below the gasket on the primer pump? Also, not for sure what 638 Loctite is?

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Rebe

Google to the rescue:

I bought two bosh pumps when I needed a replacement. First one leaked after a few months around threads. After I removed it, I needed a new crush washer. Tried dealer and they gave me one, but it was not exactly correct and leaked.

So Installed the second new pump. This time I used a high temperature oil resistant silicone. I did what I could to get all fuel out of female socket pump screws into so sealant had some chance of sticking. I also spent some time cleaning up the surface that the crush washer mates with. It seems to have worked.

The Loctite product sounds ideal.

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

The white pumps are notorious for leaking, so most people replace them. It is hard to get off since very hard to get a wrench on the lower nut. I managed (and kept my pump), but if I did again, I would just smash off the plastic top as I read others did. The new black pump goes on easy. As I recall, a deep metric socket can fit over the body and reach the nut.

BTDT.
Easy R&R job esp. if you follow instructions in this link (found searching on "Primer Pump"):
Here's my payback! Diesel Primer Pump Replacement

Suggest you avoid RTV, it is difficult/impossible to clean up later and if you use it around oiling system, say VC gasket, and blobs break off and get into the motor oiling system it is bad news. If you want to use sealant on either side of the crush washer, I'd use a very thin coat of more conventional fuel resistance gasket paste or better Hylomar/Hylomar equivalent (that's what I used). Doubt you need any sealant on the threads since the crush washer shouldered against unscratched surfaces should be the only seal you need. Whatever you put on the threaded portion(s) can form debris later as you run the male threads down into the threaded bore.

As an old plumber I use Rectorseal, the plumber's friend on oil and gas fittings. Like all sealants it has to be used sparingly and just on sealing surfaces, not smeared over the fluid path. It also has little tendency to migrate like loose threads of Teflon tape.

The pump is here and I'll install it as soon as some other bits I have on order get here. Might as well make a day of it when I start wrenchin'.

Dan

But your Mercedes should not be compared to house plumbing. I agree with everything grant1983300sd says, i.e. don't use any sealant. Clean the mating surfaces well and use a new crush washer and torque to spec. If you do not have a crow foot wrench, a vise grip will remove the old primer pump. It's junk anyway so who cares if you destroy it?

edit: As i recall, the old primer pump takes a different size wrench than the new.

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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

x2 on both points.

IIRC the new is 17mm.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Uh. nooooo. Rectorseal is used on everything from boilers to space craft. Any applied sealant must be used SPARINGLY and can help with new parts going on old parts that may no longer be flat and perfect. I'm sure Mr. Bosch made the new primer pump to the highest standards and he also made the pump to the highest standards - 30 years and somewhat more than 200K miles ago. But this is today and it's probable that all is not what it used to be. In fact, Bosch TELLS you to use sealant in the instructions packed in the box with the new pump and I'll bet they just might know what they're talking about. I was just mentioning which particular sealant I was going to use.

Dan

I learn something new nearly every day.

Fortunately, the five black button ones I replaced have not leaked, using the appropriate seal ring.

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83 SD

84 CD