All,

My vacuum pump on my 1982 300SD bit the dust recently. I'm only pulling 10-15" of vacuum on it and it's not a smooth vacuum at all, it is very jittery. I checked the pump check valve and all the components were gone missing. Looking inside the pump I didn't see anything.

I've got a vacuum pump from a junkyard that I plan to install (since the bits from the old check valve are inside the existing vacuum pump).

I tried getting started last night but can't seem to find a allen wrench that actually fits correctly. 5mm is too small it seems and 5.5mm is much too large.

In my attempts I've stripped a couple of the bolt heads. I've used vice grips to get 3 of them out, but the one in the passenger side middle of the pump I can't get my vice grips onto. Any tips other than pulling the radiator and AC Condenser to drill them out and use an easy out? At this point, I think that's about my only course of action.

Sorry I have to agree with your diagnosis - drill them out - well drill off the heads (with out damaging the pump) and then remove the pump. You should then be able to use vise grips / pliers to remove the shanks / stubs of the bolts.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

So you suggest drilling off the head rather than drilling into the bolt and using an easy out?

I want to prevent stripping the bolts in the future so when I buy new bolts I'm considering going with either standard hex bolts or possibly TORX (or maybe triple square if I'm feeling especially evil). Any thoughts on replacing with something other than an allen head bolt?

First of all, if you've got most of the bolts out and only have this one or a couple holding the VP on, you could have tremendous spring pressure pushing the VP away from the block and binding up the bolt. Install a couple other bolts enough to remove this pressure, and try again with the vice grips.

Other options that have worked for me:

Easiest and fastest, weld a new head on it. Clean with carb cleaner, LET IT ALL EVAPORATE, then weld on a nut. Use a series of tacks with cooling time in between to keep from overheating anything.

Cut flats across the socket head with a hacksaw or grinder so that you can get purchase with a large straight blade screwdriver.

Grind flats on two sides of the socket to grab with an adjustable wrench.

Use the closest fitting Allen wrench you have. Place it in the socket, and then use a center punch and a hammer to tighten up the flats of the socket towards the Allen wrench. Once you've got the socket tightened up as much as possible, have a second person use the punch and hammer to drive the bolt counter-clockwise while you apply as much force to the Allen wrench as you dare. This works best when you feel it starting to give but it hasn't actually stripped yet.

If you do wind up drilling it out, try it with a left-handed drill bit. You may find out don't have to drill much before it grabs and releases.

Obviously some of these will preclude doing others. I don't like grinding or filing flats on the outside, with a smaller fastener cutting a slot for a straight blade screwdriver is usually stronger, and of course this negates the center punch method above.

Good luck.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Pick up a left-hand drill bit of appropriate size (maybe 1/4" or so) and drill it out with that. It doesn't always work but sometimes it'll screw out the bolt in question once it grabs. If you get the right size the worst that happens is that you're left with the right size hole to tap a thread into.

Suspected cause of your problem in the first place: Those socket heads love to build up crud and it can become impossible to get a hex wrench in the hole. It's probably a 6MM but with a layer of a sort of scale that builds up inside. I use a tiny screwdriver (we call it a "tweaker") and vigorously scrape the socket on the sides as well as on the bottom. I use an hex socket and sometimes add an extension so I can pound it into the screw head. They can be a PITA!

Dan

I have only gotten 3 bolts out, but I'll put them back in to relieve tension. I don't have access to a welder and I'm not a huge fan of the grinding flats into the bolt. The access is such that this particular bolt is pretty much impossible to get to with anything other than a standard allen wrench (even a socket allen is tough to get in there).

I've thought about trying to pound a slightly larger TORX into the allen head, but I haven't been able to find a size that will work well (T30 is too small, T40 is too large. Maybe if I could find a T35...)

I'll look into buying the left hand drill bits, that sounds like a decent option.

fwiw access in there is a lot better with the radiator and fan shroud removed. you dont have to remove the condenser.

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1981 NA 300D 310k miles

If I can remove (or just move) the condenser without having to remove the AC lines I think I'll do that. If I have to remove the lines I'll probably pass since I like my AC working and don't feel like recharging it right now...

what i'm saying is there is plenty of room by just removing the radiator. the condenser will not be in the way.

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1981 NA 300D 310k miles

Enough room to get a drill in there? I'd be a little surprised if that's the case, but I'll give it a shot tonight.

You might put the Bolts back on the Vacuum Pump tighten it down and rob the Check Valve off of the Junk Yard Pump and screw it into the Original Pump and see if that fixes it. At least it could by some time.

Quite a few People have had parts of the Check Valve drop into that passage and the pieces don't seem to migrate any further into the Vacuum Pump because there is another Valve down in there.

In the pic the yellow area is the place where the parts drop. In the pick the backwards #2 is the other Valve that keeps the parts from gettinginto the innards of the Pump.

I would say just to remove the Front Cover to get at the Valve and the space behind it but I sheard off 2 of the little cover screws when I took My Vacuum Pump apart.

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84 300D, 82 Volvo 244Gl Diesel

If someone has not mentioned it People have said if you find t slighly overzied Torx bit and pound it in to the Allen Head you can remove them. Not sure what is left of the Torz bit after that.

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84 300D, 82 Volvo 244Gl Diesel

The VP cam rides a little wave shaped track on the face of the timing gear.

If you happened to stop the engine with the pump at the high point on the timing gear it will be murder trying to get it out if you don't relieve the tension first.

Rotate the engine (27 mm on the crank pulley) clockwise to pull the pump roller down into one of the valleys. That will take the load off the VP bolts.

Likewise when you go to put it back on it will be much easier if you rotate the engine so that you are in the low part of the wave when installing.

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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've already tried a check valve from the junkyard and it didn't seem to work. In fact, it seemed to make things worse. I've already pulled a pump from the junkyard, it's just these damn bolts that are stopping me. I got one more out tonight by cleaning the head out really well with carb cleaner and Q-Tips. There's still one more to go.

I'll try rotating the crank a bit to see if the piston is on an up or down stroke and give it another shot. I just hope it's not hopeless. :-P

I used one of these to remove some stripped bolts on the oil pan with great success. The only question is whether you've got clearance to fit over the head of the bolt.

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Current Stable

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