Tampa 928s

I am hearing a slight noise on the air pump what will happen if I install a smaller belt for the fan and by pass it?

928drvr86.5

Your catylitic converter will plug up without the pump's supply of air.

Tampa 928s

Any one rebuilt one of these or has a used one?

Schocki

Not true. If you disonnect the air pump nothing will happen. I drive my GTS without an air pump belt for more than 2 years. No problems no difference. The cats are not going to plug up.

The air from the pump is only necessary for emissions at high RPM's and power demands. E.g. Autobahn driving.

blown 87

I think the air from the pump is only needed during the first few minutes after cold start up to aid in the cat lighting up.

Imo000

I have one off the parts car ('86.5). If interested send me a PM.

Tampa 928s

If I bypased it there is no way of using the fan no adj would have to go electric.
I want to take the 200 mile trip to Sebring then will address it after.

Imo000

Do a search on this. Others have used a smaller lawn mower belt to run the fan directly from the crank. If you get the correct length belt it will be tight regardless that there is no way to adjust it. I think it's a 24mm belt but just to be sure run a seach.

davek9

I have been running w/out air pump over 10 years, it was removed by PO and an adjustment idler was put in it's place.
I have even passed emissions in NJ and DE with it back when I lived in those states.
Car run GREAT... now thinking of removing the CATS when I install an X pipe in the spring.
I allso know others in MI that are running the lawn mower belt w/o issue.

Mark

If you DON'T bypass or replace....the noise is likely the bearings in the pump going bad. When it seizes, the belt is gonna take the fan out with it...and hopefully won't break anything else when it slaps around when it snaps.

EASY to replace the viscous fan with an electric (or - use the lawnmower belt trick to bypass).
Advantage of going electric - gives MUCHO more room to work in the front.

MGW-Fla

The size belt is either a 21" or 22". Mine took a 21" but some here have said a 22" worked for them. You can get either size in a Gates belt from NAPA for about $5-$6 each.

PorKen

The air pump, along with these older 3-way cats, reduce NOx in the rear section of the cat. It won't plug up if you disable it.

AFAIK, the belt is either 20" or 21", depending on if you have option M319 - (fan/belt info)

MGW-Fla

well.... I always say that my memory is fadin as fast as my hairline, & I trust Ken's expertise...... guess the common denominator is a 21"... and pretty sure thats what mine is!

928drvr86.5

There have been threads on this list in the past where more than one person has mentioned plugged cats shortly after removing the air pump. Whether it's true or not i do not know. I ****canned my air pump and am running a catless crossover myself.

928drvr86.5

Oh yeah, the 21" belt worked for my 86.5, the 22 was too loose.