AIR Pump disassembly

[Michael B.]

This must have been sitting under water or out in the rain for years. The internals are completely rusted and not at all usable. I have a basic understanding of the components and how they work. What I have now is the aluminum housing with the rear cast metal cover removed. Looking at it from the back there is a metal barrel inside. The center shaft, which I believe should have come out with the rear cover, remains inside the barrel with the vane attachments rusted to the shaft.



Can anybody tell me how to finish stripping down this pump? Particularly the front hub and bearing removal.

[Lawrence M.]

Re: AIR Pump disassembly

Michael,
You can search the archives here on AIR pumps, there are a few threads.
Yes the pulley hub and drum rotate together. The 68-69 pumps were not serviced except for the filter on the front. The 1969 Shop manual has no instuctions on rebuilding the pump or taking it apart except for replacing the filter fan.
From what I read on other forums the front bearing behind the filter fan is locked in place by injected plastic. You need a press to remove the bearing. How to reinstall the bearing and get it to stay in place I do not know. When I devaned my pump over the winter I did not remove the filter fan, front bearing or the drum.
There is usually an ad in the Driveline from a member who rebuilds the pumps. Perhaps he can help you .

Larry

[Harmon C.]

Re: AIR Pump disassembly

The bearing is held by plastic and the case may break if pressed out. In my testing on junk housings the inside needs support to not break the case. With out the drum removed their is no way to support it. This could be a job for a pro to save the dated case.

[Michael B.]

Re: AIR Pump disassembly

I did see the injected plastic port holes on either side of the bearing. I can remember BOP drivelines in the 60's and 70's using the same technique to hold the U-Joints in place. We used to heat them up with a propane torch until the plastic oozed out then pressed the joint out.

I spent quite a while finding this dated part and I paid the premium so I don't want to muck it up. I'll wait for somebody with some specific answers and if not I'll check with Bill Hodel.

As for the manuals, there is a Chassis Service Manual, which most of us have, and then there is a Chassis Overhaul Manual that is supposed to give you detail on overhauling componets such as the rear end, transmission and such that the service manual doesn't cover. I have wanted a reason to buying one of these for years and this was it. I hope it has the info I'm looking for. If not, it will still be a good reference manual that I don't have now.

[Grant W.]

Re: AIR Pump disassembly

Hi Michael
I used one of those balancer pullies and pulled off the front bearing. The one with 3 holes that hold the pulley.
Then I used a press and pressed out the barrel.
Just some careful pressing off and on.
I wouldn't have smacked off the back as you could have cracked the housing. All you need now is a replacment back cover and the pins put back.
Does this help.
What was the date code you needed.
Grant

[Harmon C.]

Re: AIR Pump disassembly

Hi Michael
I used one of those balancer pullies and pulled off the front bearing. The one with 3 holes that hold the pulley.
Then I used a press and pressed out the barrel.
Just some careful pressing off and on.
I wouldn't have smacked off the back as you could have cracked the housing. All you need now is a replacment back cover and the pins put back.
Does this help.
What was the date code you needed.
Grant

If the shaft presses out then you can suport the bearing for removal.
Heat on the plastic may help.

[Joe L.]

Re: AIR Pump disassembly

I did see the injected plastic port holes on either side of the bearing. I can remember BOP drivelines in the 60's and 70's using the same technique to hold the U-Joints in place. We used to heat them up with a propane torch until the plastic oozed out then pressed the joint out.

I spent quite a while finding this dated part and I paid the premium so I don't want to muck it up. I'll wait for somebody with some specific answers and if not I'll check with Bill Hodel.

As for the manuals, there is a Chassis Service Manual, which most of us have, and then there is a Chassis Overhaul Manual that is supposed to give you detail on overhauling componets such as the rear end, transmission and such that the service manual doesn't cover. I have wanted a reason to buying one of these for years and this was it. I hope it has the info I'm looking for. If not, it will still be a good reference manual that I don't have now.

Michael------


It's been so long since I disassembled one of these pumps that I've long since forgotten anything about it. I vaguely recall that I rebuilt one once-upon-a-time but, while it functioned properly after the rebuild, it was very noisy. So, I gutted it and re-installed it on the car that I was trading in anyway (and getting almost nothing for).

Please let me know if the overhaul manual has the AIR pump information in it. I have a 1970 Chevrolet (and 1969 Corvette) Overhaul Manual and it has no information, at all, regarding AIR pump rebuild. It's possible that earlier manuals might, though. The 68-75 pumps were all the same internally. 66-67 and 76-82 are somewhat different, though, but I think they're pretty much the same basic design.

By the way, I think I know what caused the problems that your pump apparently suffered. This sort of problem is caused by failure of the check valves. When the check valves fail, exhaust gas can back-flow into the pump and this completely destroys the pump, causing massive internal corrosion and, often, seizing of the pump.

I have an old 1989 Cadillac El Dorado that my late father purchased new. On one biannual smog test several years ago the car barely passed. The pump looked like it was working fine but when I checked it, it was not putting out any air. So, I replaced it with a new one (not rebuilt) and when I had the old one off, I opened it up. There was virtually NOTHING inside, but the front bearing, hub, and pulley turned beautifully; smooth and nice. What was left inside was heavily corroded, looking like it had been "underwater" as you described. So, I figured I better check the check valves. Both were TOTALLY gone and that was the root of the pump's problem. I also learned that the exhaust back-flow had destroyed the control valve which is about a $400 item.

Lesson to be heeded: folks with AIR-equipped cars, especially those with dated or otherwise valuable pumps and valuable diverter valves (almost all original diverter valves are highly valuable) need to check their check valves periodically lest their highly valuable pumps and diverter valves be destroyed.

Another thing to keep in mind: the "reconditioned", original-style check valves available in the Corvette parts marketplace are re-plated, USED valves. Of course, these valve are checked for functionality before they are replated and sold. However, while they may be OK at that time, who knows how much life is left in them? Remember, these are USED valve, NOT new. They are also a LIFE-LIMITED component and some of their life is already "used up" when you get them.

There are also NEW valves on the market but their configuration varies slightly from the originals and they certainly don't have the stamped part number everyone wants. But, they are NEW and part of their life is NOT "used up" when you install them.

[Terry M.]

Re: AIR Pump disassembly

Another thing to keep in mind: the "reconditioned", original-style check valves available in the Corvette parts marketplace are re-plated, USED valves. Of course, these valve are checked for functionality before they are replated and sold. However, while they may be OK at that time, who knows how much life is left in them? Remember, these are USED valve, NOT new. They are also a LIFE-LIMITED component and some of their life is already "used up" when you get them.

There are also NEW valves on the market but their configuration varies slightly from the originals and they certainly don't have the stamped part number everyone wants. But, they are NEW and part of their life is NOT "used up" when you install them.

One also doesn't know what effect the acids used in plating will have on the check valves. I am sure it will not extend their usefull life, however.

[Lawrence M.]

Re: AIR Pump disassembly

Michael,

There is no emmisions section in the 1970 Chassis Overhaul Manual.

Larry

[Joe L.]

Re: AIR Pump disassembly

One also doesn't know what effect the acids used in plating will have on the check valves. I am sure it will not extend their usefull life, however.

Terry------


The thing about check valves is that they always look fine from the outside. Plus, when they fail, they exhibit no obvious symptoms; the engine continues to run just fine. Some folks even think these things are "immortal". They are FAR from being "immortal", though. They are a very life-limited component.

[John H.]

Re: AIR Pump disassembly

The '67 Chassis Overhaul Manual has a very complete and detailed chapter (section 6T) on rebuilding the pump, but the '69 manuals have virtually nothing (new pump design); don't know about the '68 manuals.

I had Jerry MacNeish "gut" the pump on my '69 Z/28 so it's simply an idler pulley, to avoid the chronic failure mode (vanes seized to the housing) that destroys the pump. Also removed the tubes in the exhaust manifolds and replaced them with #10 x 1/2" flat head machine screws before re-installing the air manifolds to eliminate backflow of exhaust gases that can discolor the difficult-to-reproduce plating/coating on the air manifolds.

[Michael B.]

Re: AIR Pump disassembly

John,

I have a 1967 Chassis Service Manual for a Camaro that I have and that manual indicated that the Overhaul Manual had detailed information on rebuilding of the pump. I was hoping that that had carried through the later years but it doesn't sound like it. I'm sure the process and techniques are similar if not the same though.

I took some pictures and I'll post them later when I get home.

[Terry M.]

Re: AIR Pump disassembly

The '67 Chassis Overhaul Manual has a very complete and detailed chapter (section 6T) on rebuilding the pump, but the '69 manuals have virtually nothing (new pump design); don't know about the '68 manuals.

I had Jerry MacNeish "gut" the pump on my '69 Z/28 so it's simply an idler pulley, to avoid the chronic failure mode (vanes seized to the housing) that destroys the pump. Also removed the tubes in the exhaust manifolds and replaced them with #10 x 1/2" flat head machine screws before re-installing the air manifolds to eliminate backflow of exhaust gases that can discolor the difficult-to-reproduce plating/coating on the air manifolds.

1967 Overhaul Manual is the one and only AIR pump overhaul instructions. I guess in later years it was supposed to be R&R, not rebuild.

[Terry M.]

Re: AIR Pump disassembly

Terry------


The thing about check valves is that they always look fine from the outside. Plus, when they fail, they exhibit no obvious symptoms; the engine continues to run just fine. Some folks even think these things are "immortal". They are FAR from being "immortal", though. They are a very life-limited component.

Yes, folks do think the check valves are immortal. They function in a very hostile environment. First thing I did with the Camaro when I got it was change the check valves, but there is a TSB for the Caprices that allow for disabling the AIR pump. They didn't have to tell me twice -- it was gone in less than 30 seconds, and it was electric driven so no load on the engine -- still gone.

[Michael B.]

Re: AIR Pump disassembly

Here are some pictures of what I have. This pump was not coming apart in one piece. I bought this pump knowing it was siezed but I thought I'd at least be able to get the back off it.

My car is a October 4 1968 build date and the pump is dated 23881S, late August 1968. Too much earlier and the dates were going to be for the 68 style with the relief valve so this was a litttle hard to come by.