Vacuum pump 1985 300SD reliability ? - PeachParts Mercedes-Benz Forum

yuke · #1 09-30-2015, 09:00 AM

Was wondering about the vacuum pump on my 85 300SD.
1. Is it prone to fail?
2. If it fails are you stranded? Even if you have a mityvac with you?
3. What fails in them and are they easy to rebuild?

Reason I'm asking is I use this car for long trips and am trying to avoid getting stranded hundreds of miles from home.

CarpeDiem51392 · #2 09-30-2015, 09:43 AM

1. No they're not know to fail like the 60x engines. We've heard stories of them failing though even on 617s so it does happen.

2. Don't think so you lose all vacuum but could still theoreticaly drive BUT don't

Likely if it does fail there are metal chunks loose in the engine, so don't chance it!

3. I'm not sure for a 617, it's usually the bearing or roller race for 60x. They're probably "rebuildable" but might be tough to find the parts.

If you're worried about it then swap it out, it's an easy DIY but the pumps themselves are a little pricey if you plan on keeping the car I would say it's worth it. My pump looked brand spanking new after 150k, this was one of the dreaded open bearing 60x pumps.

Cheers

Charlie Foxtrot · #3 09-30-2015, 10:33 AM

What symptoms are you having?

Wore out a vac pump on an 85 300SD/W126 back around Christmas/New Years. About 475,000+ miles on the car (about 275k on the pump) . It slowly stopped creating vacuum. Very difficult to shut off engine w/key & lost power assist to the power brakes.

The loss of reliable power brakes is a BIG issue with the car, especially in the snow & ice.

Mity-Vac won't help. You can shut the engine off using the 'stop' lever at the IP. I can't think of anything that would help w/brakes. Good luck.

mach4 · #4 09-30-2015, 10:40 AM

There's realistically only three things in them that can fail - the bearings, the piston and the check valves. It's theoretically possible for the arm to fail, but very unlikely. The rebuild kits have valves and piston seal but no kits have the bearing. The bearing is easy to replace, but it's a treasure hunt to find the right one. Search the threads and you'll find numerous references to the bearing size (626) but it's more than critical to get the right bearing. (Some bearings are designed for drawer slides and some for critical industrial applications) No references to actual part numbers have ever been posted to my knowledge. The best strategy would be to break down the pump and take the existing bearings to a reputable bearing supply house.

If the pump fails you won't be stranded unless the thing grenades and the shards take out the engine.

Your brakes will become manual and your engine won't stop - that's about it for anything important.

jay_bob · #5 09-30-2015, 10:41 AM

Ask vstech what happens when the vac pump lets go on a 617...

... boom. check your vacuum pump!

dude99 · #6 09-30-2015, 10:42 AM

1. Is it prone to fail?
A: Not really.
2. If it fails are you stranded? Even if you have a mityvac with you?
A: mitycav won't make a difference, but you won't technically be stranded. The car will run and drive, but you won't have power brakes, and the 300SD is a very heavy car to stop without them.
3. What fails in them and are they easy to rebuild?
A: usually the rings in them go (they are made of some sort of composite material, not really sure what it is) or the check valves fail (either one of the two smaller ones stick or the big brass one fails). They are easily rebuildable and can be done at home fairly simply. IF you do rebuild it be sure to get the gasket that goes between the pump and the block, most kits don't come with this.

kestreltom · #7 09-30-2015, 12:22 PM

Since you can't get a rebuild kit anymore from resellers, I decided to do my own rebuild. I had a junkyard pump and the pump off my '84 300D and between the two of them I made the best rebuilt I could.

The bearings that you are looking for are SKF 626-2Z or SKF 626-ZZ available from Motion Industries

*************the above image is from Stretch's excellent post on rebuilding the 617 vacuum pump ***************

The Mercedes Benz dealer-only rebuild kit part number is

000 586 17 23

My junkyard pump was badly scored on the cylinder walls but the check valves were in good shape. Both of the main checkvalves that screw into the pump body were leaking pretty bad, so I used carb cleaner, brake cleaner, and a Simple Green soak to get one of them to seal again. Since I did not have a rebuilt kit I used the best rubber gasket to close it up with the help of a slight smear of silicone sealer that had skinned over. I am getting about 17 inHg - which is good at my altitude (5000 ft)

Here is Stretch's rebuild link to read

mannys9130 · #8 09-30-2015, 12:27 PM

Here's Stretch's magnificent thread for you to read. If you're concerned, rebuild it. Better to rebuild it a little early rather than wait till it fails or grenades anddoes more damage. The 61x pumps don't fail like the 60x ones do, BUT when they do the failure leads to the same end, which is a snapped timing chain if one of the ball bearings gets picked up into the camshaft sprocket.

More than you are likely to ever want to know about OM61X piston vacuum pumps

charmalu · #9 09-30-2015, 12:46 PM

There is hundreds of Vac Pump threads....here is a excellent thread by Beagle.

VACUUM PUMP FAILURE! Are you neglecting yours??

A few more.......there will be a test at the end of the week.

Will these bearings work for a vacuum pump?

Vacuum Pump Rebuild -Foolish Not to Replace Bearings?

Vacuum pump rebuild?

'85 300D Vacuum pump question

Charlie

sent from my pos computer

BillGrissom · #10 09-30-2015, 02:59 PM

Usually, the failure is "doesn't produce vacuum". You know because the engine won't shut off. Until you can fix it, you can run a nylon tube into the cabin (or tap existing one) from the "stop valve" and use a Mighty-Vac to stop the engine (then release vac so you can restart). Happened in my 1984. I bought the rebuild kit for $105 on ebay. It is a piston seal, check valves, and rubber gasket. Got me back to a nice 22" Hg vaccum.

Worse is when the bearings go, as happened in my 1985. The pump still works, but makes a rattling noise. By the time my son got it home, it had worn mostly thru the arm. A bit more and the arm would have broke off and probably slid into the cam chain (bad result). I had a spare pump. There is/was an arm w/ bearings kit on ebay for $99. I think you can still get the seal kit. I bought a bunch of the above bearings on ebay, but they arrived after I had to get the car back to my son.

Long-term, I want to try an electric vac pump one one of my 300D's, with a cover where the mechanical vac pump sat.

dude99 · #11 09-30-2015, 03:35 PM

Quote:

Long-term, I want to try an electric vac pump one one of my 300D's, with a cover where the mechanical vac pump sat.

Many have tried this. The issue is that the automatics in these cars have a constant leak, so the pump ends up cycling very often and over heating. I would imagine that with a manual transmission it would be very doable.

I also saw a thread the other day where a fellow put a belt driven pump from a ford power stroke on his OM606 or OM602 (can't remember which).

kestreltom · #12 09-30-2015, 03:56 PM

Since I had already upgraded to a 140 amp alternator, I also added an electric Hella UP28 vacuum pump from a late-ish model turbo Volvo, since it was a 10 buck U-pull item. The electric pump is tied into the functioning original rebuilt vac system upstream from the 1st check valve as a backup pump, and it is controlled by a vacuum switch set to 16 inHg. The pump makes a barely detectable whine over the engine sound... sounds kind of high tech. The electric pump pulls about 8 amps. I attached a cpu cooler to the top of the pump to keep it from getting too hot, since these things run at up to 220 degrees F - and mounted it using the original Volvo bracket modded to fit over the driver side upper shock mount.

Summit Racing sells a better Hella pump that can easily power the brake booster by itself for about $250.00 which is at least 100 bucks cheaper than a new Mercedes / Pierburg pump, and won't dump parts into the timing chain when or if it fails.

mach4 · #13 09-30-2015, 04:10 PM

Quote:

Originally Posted by BillGrissom

Long-term, I want to try an electric vac pump one one of my 300D's, with a cover where the mechanical vac pump sat.

Before you head down that path, you might want to read this - Electrical Vacuum Pump Conversion Project

Diesel911 · #14 09-30-2015, 06:57 PM

My question What in particular causes vacuum pump failure?

What in particular causes vacuum pump failure?

BillGrissom · #15 09-30-2015, 10:58 PM

Quote:

Originally Posted by mach4

Before you head down that path, you might want to read this - Electrical Vacuum Pump Conversion Project

A very interesting 9 page discussion and you did very detailed work. The main discrepancy is that you found (post #84) that, even running continuously, your electric vac pump couldn't keep up with the steady-state bleed thru the restrictor and VCV (measured 12"Hg vacuum), but several other people reported that their electric vac pump worked fine in daily use. The one test I didn't see is to block the VCV vent tube and verify you then saw the full 22"Hg vacuum. That would better assure that the VCV bleed was the problem and not a leak somewhere else (split hose, tranny modulator).

I wish I could find a <$20 vac pump to play with. All the used VW & Audi pumps I see on ebay are >$35 + shipping.