1970s A.I.R. pump information

[caddydaddy1960]

Greetings,

I own a 1974 Eldorado convertible with 50,000 miles.  Recently there has been a grinding noise coming from the A.I.R. pump located under the alternator.  My mechanic tells me the pump is likely failing.
He is not familiar with this system nor am I.  Is it possible just to take the drive belt off the pump and drive the car without it? I'd like to keep the vehicle as original as possible, but want to be able to drive it until this issue is resolved.  He also stated that he has seen similar vintage vehicles with this system removed.

Any information or advice would be greatly appreciated.

Many thanks,

Michael Heinz
#27227

[The Tassie Devil(le)]

G'day Michael,

The way the factory designed the belt-drive off the crankshaft does not allow for the simple removing of the belt that drives the AIR Pump.

It can be removed, BUT, the Alternator will not drive as this is driven directly off the Water Pump, which is driven by the AIR Belt.

Many have removed the AIR and relocated the Alternator rearward to align with the AIR belt, using a different length belt.

Removing the AIR requires the blocking off of the AIR Manifold that supplies the air to the front of each Cylinder Head.

Bruce.

[caddydaddy1960]

 Greetings Bruce,

Many thanks for your input.  I guess I will go the route of replacing the pump with a rebuilt one.  Luckily they seem readily available.

Michael

[Roger Zimmermann]

You may also just purchase the bearings and replace them. On my '72, I went further: I destroyed the vanes, so the pump is just here for the belt. I also pluged the air manifold as indicated by Bruce.

[TJ Hopland]

What usually kills the pumps is the check valve fails and lets the corrosive exhaust backflow down into the pump.  The check valve is the fitting looking thing where the hard cross pipe between the heads transitions to the hose.  Easy to check, just pull the hose off and see if exhaust comes out.

The other thing that gets taken out by the backflow is the diverter valve.  If that is stuck open you get a popping backfire sort of thing in the exhaust on deceleration or if there are other problems brewing possibly an exploding muffler if you are really unlucky.

There were some years that didn't have that setup and used a different pulley setup but that isn't as easy as you would hope either because there was single and dual groove for the AC/PS belt (74 could have had either) and to convert you then have to do the AC and PS pulley (possibly pump too since around 74 those too changed from bolt on to press on).  If you do try to go that route you want to get at least the 3 piece set off the same engine which is the crank pulley, water pump pulley, and timing gauge. 

I think Bruce at one time posted pics of the move the alternator back option and IIRC he is using a different than the typical alternator so that option also isn't as easy as you would hope for.  If you can get a pump and the diverter valve isn't fried that is likely going to be the easiest and least expensive route.  I would keep the old pump because it could turn out that the new one is junk at which point possibly being able to get bearings for the old one may be worth the trouble.

Again from memory I think the diverter valve is connected to a 'ported' source on the carb meaning that when the throttle is closed there is no vacuum signal which means the valve will be diverting the air from the pump out the little exhaust port on the valve assembly.  Once the throttle is open it gets vacuum and the valve opens and sends the air up to the heads.  There may be a time delay function to it too because I think after some time after the throttle closes (seconds) it starts sending air back to the heads too.  Its just that few seconds around decell that its not sending air to the heads.  I think that timing function is part of the valve assembly itself.

When as the throttle is closing vacuum rises so you get a rush of fuel drawn in as you are closing off the air source so things go way rich and you get unburned fuel out the exhaust.  If the AIR system was pumping fresh air in at that time it will burn giving you that popping or possibly a big boom so thats why they have the valve that diverts the air for that transition period when you don't want it.  Otherwise that the systems job, inject some fresh air into the exhaust to let it finish burning and doing its chemical stuff to turn it into less bad stuff before it comes out the tail pipe.