serpentine belt

Chris Streett

Asked by Dec 22, 2015 at 07:49 PM about the 1990 Ford F-150 XLT Lariat LB

Question type: Maintenance & Repair

Can I use original serpentine belt for 1990
ford f150 with a.c. and bypass a.c. and
smog control units. If not what size belt do I

6 Answers


No you will not be able to use the original belt. The rout will be shorter. What I did was figured out how I wanted to run the belt, then took a string threw that path and went to the parts store an matched up the proper length to a new belt.

3 out of 3 people think this is helpful.
Guy Outland

That's how we made the "short" belt for bypassing all the pulleys when racing mustangs back in the day.

1 out of 1 people think this is helpful.

By "smog control units" do you mean the air pump that introduces air in to exhaust stream... to help burn off excess unburnt hydrocarbons to reduce emissions? What other device that is driven by the serpentine belt could you be referring to if not that? That air pump is there for a reason, otherwise ford would not have gone to the expense of putting it there. Usually those air-pumps are only in Calif emissions package. To eliminate A/C compressor you need an idler pulley, and put the air pump back on

2 out of 2 people think this is helpful.
Guy Outland

Again with that smog thing? You crazy C.A.R.B. people. Chris the air pump does not rob your engine of enough power to take it off for no good reason, As Fordnut states it was put on the truck for a good reason. If the truck does have cats then they will be prone to clogging if the pump is removed and the a/c pulley is just an idler if the compressor isn't engaged.

1 out of 1 people think this is helpful.

Right on Guy. Thanks for the conformation of my answer.

2 out of 2 people think this is helpful.

As someone said, the pulley on the a/c spins freely if the a/c in not turned on. If there is nothing wrong with the clutch on the ac, and it is not rattling, leave it on there. Same goes for the pump. You will probably have to rig some sort of compensator pulley or you may start loosing the belt while driving.

1 out of 1 people think this is helpful.

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