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How to De-Vein or Rebuild Your GM Smog Pump

Technically Speaking: Breath of Fresh Air, Part Two

James Berry May 6, 2015
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(Editor’s Note: Please check your local DMV/Smog regulations as de-veining the smog pump may be an illegal modification for a street registered and driven vehicle.)

This month we are going to roll up our sleeves and get right to work. We are going to start off by de-veining or rebuilding a smog pump.

De-Veining or Rebuilding a Smog Pump

When you de-vein a smog pump, the pump will spin freely but not pump. The reason some people chose to de-vein their smog pumps is that over time the smog pump can fail internally and make noise. Or, more specifically, the diverter valve can fail and cause a backfire on deceleration that could damage the exhaust system. Making the smog pump non-functional will not affect the driveability of the vehicle, and once the smog pump has been de-veined no one will be able to tell that the pump has been turned into a non-functional unit.

Remember, smog pump systems were designed to introduce clean air to the engine exhaust to help unburned hydrocarbons to continue to be burned as they travel down into the exhaust system and ultimately out the tailpipe. So by de-veining your smog pump you are altering the original emissions control systems, and none of us want to cause more global warming. So you will need to make a decision to de-vein or rebuild, the process is similar no matter which method you choose.

01. Remove the four bolts and push the two retainer pins from the back cover. Use two blocks of wood to sit the pump on so the plastic fan will not be damaged.

Smog Pump Remove Rear Cover 2/4

02. Separate the rear cover from the cylinder housing. You may need to pry the two assemblies apart; two or more chisels or screwdrivers can be used for this process if necessary. After the assemblies have been separated take note of the fan blades inside the cylinder housing.

Smog Pump Remove Fan Blades 3/4

03. If you are de-veining the pump, use a hammer and a large chisel to break apart the fan blades and components located in the cylinder housing. Inspect to confirm that all of the small pieces have been removed from the cylinder housing; some small pieces may be imbedded in the cylinder slots.

Smog Pump Rear Bearing 4/4

04. If you are rebuilding the pump and replacing the fan blades – the rear bearing and race will need to be removed. Skip to step #6.

05. If the pump was spinning freely before disassembly, clean the aluminum housing, and grease the rear bearing. If the pump was not spinning freely before disassembly, one or two of the bearings will need to be pressed out and replaced.

06. The rear bearings can be removed using a small slide hammer. The rear bearing is pressed in. If the bearing and race does not come out easily, some heat may be needed to aid in removal. With the retainer out of the way the vanes can easily be removed or replaced.

07. If you need to remove the front bearing; that can be somewhat tricky. First, you must pull the front pulley off and then a press will be needed to push the shaft out of the housing, which is part of the drum assembly for the pump that houses the fan blades.

Once removed, look for two small nubs that are located at the 2 and 8 o’clock positions on the front of the housing. This is where the factory-injected plastic was used to hold the bearing in place.

To remove the bearing from the housing, the bearing will need to be cut away. To cut the front bearing out, using a Dremel tool, work from the inside of the bearing towards the outside of the bearing and slowly whittle away at it until you get to the aluminum housing. The remaining pieces of the old front bearing can then be picked out of the aluminum housing. Clean the housing and press a new front bearing into place using epoxy to reattach the bearing to the pump housing. After the epoxy dries, peen the edges of the front bearing into the aluminum housing so the front bearing will not move or try and rotate while the pump is running.

I have seen some mechanics try and melt the plastic out using a butane torch. I do not recommend this method because the plastic can pop violently and burn you or cause the housing to warp or crack. If you do not feel conformable with this operation I recommend taking this to a machine shop to have the bearing removed.

Most of the front bearings used in these pumps were made by New Departure, which was owned by GM, and is now out of business. National Bearing offers part number NTN-6203LLBC3/EM that will work as a replacement front bearing for the majority of GM smog pumps. You will find some of these front bearings are identical to the alternator front bearing, except for the grease shields.

08. Reassemble the unit.

Plugging the Exhaust if De-Veining a Smog Pump

If you are de-veining the smog pump, the exhaust ports will need to be plugged. I have seen several ways to perform this process. I have worked on vehicles where stainless steel screws were dropped in the exhaust manifold holes, which is something I do not recommend. I have also seen the air distribution manifolds plugged up, which is a fast and simple method that will not damage or cause modification to an expensive component such as the exhaust manifold. That should keep you busy until next month when we will take a look how to diagnose problems and what repairs can be made to the C4 air pump. Also, what modifications would need to be made to bypass the air pump completely?



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