October 24, 2009

Air Pump Fix Tutorial

Volvo 850, XC70, C70, S70 & 1998-2000 V70

Overview

If the air pump has failed in your Volvo 850, there is an alternative to buying an expensive new or used Volvo air pump: you can buy a rebuilt or used VW air pump and convert it for use in your Volvo.

A few questions arise when considering this course: Will the VW pump work right? How much will I save? Which VW pump part number(s) will work? How hard is it to convert? How do you do the conversion process?


The answers:

The VW pump will work right and you can save about $100-250! I bought my pump on eBay and it cost me only $36.85, including the postage. Plus, it had been rebuilt. The official Volvo part (1270558) costs around $295 new and around $150 used. Working used Volvo pumps are somewhat difficult to find probably because they fail in service due to corrosion.

Note: before replacing the air pump, I removed the old SAS valve (Volvo part 9125623) and replaced it with a new one. I have read that the underlying cause of a failed pump is failure of the SAS valve to close, allowing water from the exhaust stream to condense in the pump, causing corrosion and eventually motor seizure.

There are likely other sources besides VW air pumps, but the one that I used is VW part 021 959 253C. The VW parts 021 959 253B and 037 959 253A are similar and would probably work. The 021 959 253C that I bought was made by Pierburg, just like the original Volvo air pump. I think the 021 959 253B and 037 959 253A are made by Pierburg also.

Whichever pump you buy, it is a good idea to test it electrically before beginning any conversion work. I connected my rebuilt pump up to the car battery and verified that it worked. If you do this, follow standard safety practice: make sure the pump is firmly held (because it will kick when started up and could fall) and make the second connection to chassis ground and not the battery to avoid creating a spark at the negative battery terminal, which could cause hydrogen gas at the battery to ignite!

The VW-Volvo conversion process will take about two hours and requires a file, punch, hammer, screwdrivers, wire cutters, pliers, solder, soldering iron, heat shrink tubing, hacksaw, utility knife, 8-32 machine screws, bolts, washers, lock washers, tie wraps and (optional) Loctite. It’s likely you already have, can scrounge up or improvise all of this stuff.

Procedure

(1) Remove the front cover of the old pump and put it on the rebuilt/used pump (0.5 hour)

(2) Remove the rear wiring cover of the old pump, swap a connector, modify a spring retainer and put it on the rebuilt/used pump (1.0 hour)

(3) Modify the VW air outlet connector so that the original Volvo hose will fit over it (0.5 hour)

First, remove the old air pump from the car. The best instructions I have found are at Volvospeed.com. This is an excellent website for Volvo 850 repair and information! Look for the gBay 13h Maintenance area. At the time of this writing, the air pump repair link is: http://volvospeed.com/Repair/airpump1.php.

Once you have the air pump out of the car, you can begin to take it apart. The picture below shows the original rusted Volvo air pump. The Volvo pump was made by Pierburg and has Pierburg barcode ID 517048812095 on the side of the motor housing. (For reference, the VW pump has Pierburg barcode ID 536179041587.)

Following the instructions at Volvospeed, the pump has been removed from the metal frame and disconnected from the relay. In the picture below, the original metal rivets have been partially withdrawn to enable removal of the front cover. (Detail on how to remove the rivets below). You need to remove the front cover and save it because it will be installed on the rebuilt/used pump.

Removing the rivets: I used a file to remove the back head of the rivets (on the motor side). The picture shows the back of the rivet after filing off the head and before tapping the rivet out. You could file off the front head instead, but you would have to be extra careful not to damage the plastic on the front cover, which will be reused.

After filing off the heads, I used a punch and hammer to tap each rivet out of the hole. Only a gentle tap is required.

In the picture below the six rivets have been removed and the front cover has been unclipped and pulled off the pump. You can see the corrosion and rust on the fan and shaft. The motor shaft turned very roughly.

Next we turn attention to the rear wiring cover. The picture below shows the back of the Volvo motor with the clip-on wiring cover. You need to remove this part and transfer it to the rebuilt/used VW pump. Use a flat blade screwdriver to pry the three clips up and pop off the cover. Bewarea small spring under the cover may make the cover jump when the last clip is released.

The picture below shows the wiring cover after releasing the clips. You can see the spring and the positive and negative wires that connect to the spade terminals on the motor. Remove the spring and save it for now just in case (the rebuilt/used pump should come with its own spring). Disconnect the two electrical connectors from the spade terminals. Blue is positive (and wider). Black is negative (and narrower).

The picture below shows the two pumps side by side (VW on left, Volvo on right) with the rear covers removed. In the center foreground is the spring and plastic collar from the rebuilt VW pump. There is no plastic collar in the old Volvo pump because there are outer fingers in the cover and a ring built into the motor housing to hold the spring. To install the Volvo wiring cover onto the VW motor housing, you will need to use the VW plastic collar, but the upper two thirds of the collar (the narrower end of the collar that fits into the fingers) has to be cut away. I used a sharp utility knife to cut away the plastic.

The picture also shows the motor polarity: for both the VW and Volvo pumps the positive electrical connector is on the right as viewed from this position. Since the VW connectors are the same width, I drew a little + on the positive connector to avoid mix-ups when connecting the wires later.

In the picture below, the two wiring covers are shown. Upper left is the VW and lower right is the Volvo. On the VW cover, the negative (brown wire) connector has been cut off and installed on the negative (black wire) connector on the Volvo cover. This is required because the Volvo negative connector is too narrow to fit onto the VW motor negative spade terminal. In the picture, heat shrink tubing was installed over the black wire and the VW negative connector has been crimped onto the black wire and soldered.

In the picture below, the heat shrink tubing has been positioned and shrunk into place.

The picture below shows the VW pump after connecting the positive and negative wire connectors, installing the spring and cut-down plastic collar, and snapping on the wiring cover.

Next we turn attention to installing the old Volvo front cover on the rebuilt VW pump
The picture below shows side-by-side the rebuilt VW pump on the left and the old Volvo pump on the right. Note that the rebuilt VW pump already has machine screws instead of rivets holding the fan section together. This makes disassembly a bit easier than it would be on a non-rebuilt pump.

The picture below shows the rebuilt VW pump (left) and the old Volvo pump (right) after removing the front cover of the VW pump. Were going to install the Volvo cover on the VW pump and attach it with machine screws instead of rivets. I used the 8-32 machine screws that came with the rebuilt pump.

The picture below shows the VW pump after installing the front cover from the old Volvo pump. I used machine screws, washers and lock washers. For added insurance, I dabbed a little Loctite onto the threads before tightening.

In the final part of the conversion, we modify the air outlet connector so that the original Volvo hose will fit over it. The picture below shows the air outlet connector on the VW pump after cutting off the top part to make it closer to the Volvo connector (which can be seen at the rear for comparison). I used a hacksaw and a utility knife to shape it.

The picture below shows the air outlet connector on the VW pump after cutting back the support ridge on the side to give more length for the hose to be clamped.

The picture below shows the VW pump (on the right, with the old Volvo rear wiring cover installed) and the old Volvo pump (on the left). The shape of the air outlet connectors can be compared. As I learned when I tried to slide the hose over the VW air outlet connector modified as shown in the picture, the fit was too tight. To get the hose to fit, I had to take my utility knife and trim away more of the flare at the tip of the VW connector.

At this point, the pump is ready to be installed. I retested the pump electrically after doing all the wiring conversion just to make sure it still worked.
The picture below shows the pump after reattaching it to the frame using the rubber mounts, attaching all the electrical connectors and the ground wire, and bolting the frame to the car. At this point the hoses can be reattached to the air inlet and outlet. I used nylon tie-wraps to clamp the hoses in place. If preferred, you could instead use a hose clamp or crimp clamp on the inlet, but the outlet isnt long enough to fit a hose clamp only a tie-wrap or crimp clamp will fit.

Conclusion

As mentioned at the beginning, the most complete instructions on removing and installing the air pump are to be found at Volvospeed. I used them and am grateful that they were available! This write-up is mainly intended as a guide for converting cheap, abundant used/rebuilt VW pumps for use in the Volvo 850. I hope it helps you save!
Many thanks to Jason R for authoring this repair.
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Tags 850, air pump, C70, S70, Tutorial, V70, XC70
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