Work safely, check your manual. This guide is a helper, not a replacement for your factory service manual. Work on a cool engine, parked on level ground with the parking brake on. Wear eye protection and gloves. If a step doesn't match your car, stop and check the manual or ask a shop.
How-to video
The video loads from YouTube (privacy-enhanced mode) only when you tap play. These videos are made by their channels, not by us. Your routing depends on your setup. Always match your own decal.
Fox-body 5.0 video; year not stated.
Watch on YouTubeFox-body 5.0 video; year not stated.
Watch on YouTubeHow we match videos: we only call a video from another year a match when a parts catalog lists the same part number for both years. If a video doesn't say its year, we say so.
Tools for this job
Matched to the steps below. Tick “I already have it” to fade a tool out (this page only, nothing is saved).
Serpentine belt tool or breaker bar
Takes tension off the automatic tensioner so the belt slips off and on.
Borrow it freeRefundable deposit at AutoZone or Advance Auto Parts.
See price: AutoZoneSee price: Summit RacingSocket set
Only needed if you replace the tensioner (55-80 ft. lbs.).
See price: AutoZoneSee price: Summit RacingFlashlight
Lets you check every pulley groove and the tensioner marks.
See price: AutoZoneSee price: Summit Racing
About “Borrow it free” and these links
Loaner programs, checked Oct 29, 2026. Stock varies by store, so call ahead.
- AutoZone Loan-A-Tool: deposit covers the tool price, keep up to 90 days, full refund on return
- AutoZone: Loaner Serpentine Belt Tool
- AutoZone: Loaner Torque Wrench
- Advance Auto Parts Loaner Tools: free with a full refundable deposit, return within 45 days
- Advance: Loaner Tool 1/2 in. Needle Torque Wrench Kit 944050
- Advance: Powerbuilt Loaner Tool Serpentine Belt Tool Kit (listed on this page)
“See price” links open that store's search. They may become affiliate links (disclosure). We don't list prices here; check the store.
Before you start
- Difficulty
- Easy
- Time
- About 20 to 45 minutes (estimate)
- DIY or Shop
- DIY A good first DIY job. Shop if the tensioner or a pulley is noisy or wobbly and you don't want to replace it yourself.
Tools
- Breaker bar or pry bar for the tensioner
- Socket set
- Phone camera (for the routing photo)
- Flashlight, gloves, and eye protection
Parts
- Serpentine belt for your setupBelt length depends on your setup (A/C, power steering, smog pump). Match the old belt and the listing's fit notes.RockAuto (1993 Mustang catalog)Summit RacingAutoZone
- Belt tensioner (only if it fails the check)RockAuto (1993 Mustang catalog)Summit RacingAutoZone
Plain store links, not affiliate links. Each opens that store's own search. Check the store's fit guide for your exact car before you buy. Price Watch can keep looking for the best price we can find, or ask us to find the parts.
Specs for this job
- Belt adjustment: None needed: automatic tensioner. The tensioner arm should sit between its two index marks. (source)
- Belt routing: Follow the decal on top of the windshield washer / coolant expansion reservoir. (source)
- Belt routing for modified setups and belt length: Check your factory service manual or the underhood emissions (VECI) label for the exact spec.
- Tensioner mounting bolt (only if you replace the tensioner): 55-80 ft. lbs. (source)
Step by step
Engine off, key out, engine cool.
Keep hands, sleeves, and tools out of the belt path.
Find the routing decal and take a photo of your belt.
The factory decal is on top of the windshield washer / coolant expansion reservoir. Photo the belt as it runs now.
Do this before that: Do this before the old belt comes off. It is your map.
Check the tensioner marks.
Look at the tensioner arm and its two index marks. Write down where it sits.
Take tension off and remove the belt.
Put the breaker bar on the tensioner and move it to take tension off. Slip the belt off the easiest pulley, then let the tensioner back slowly.
Spin each pulley by hand.
Water pump, tensioner, idler, alternator. Listen and feel for grinding, roughness, or wobble.
Do this before that: If the water pump wobbles or leaks, replace the pump first (see the water pump guide), then put on the new belt.
Match the new belt to the old one.
Same number of ribs and the same length for your setup.
Route the new belt.
Follow the decal and your photo. Leave the easiest pulley for last.
Move the tensioner and slip the belt on the last pulley.
Release the tensioner slowly. Don't let it snap back.
Check every pulley.
Every rib must sit in its groove, centered on each pulley.
Check the tensioner marks again.
With the new belt, the arm should sit between the two index marks. If it doesn't, the belt is wrong or the tensioner is worn.
Start it and watch.
Watch the belt for a minute and listen for squeal or chirp. Shut it off and recheck the grooves.
Mistakes to avoid
- Taking the old belt off before photographing the routing.
- Buying the length for a different setup (A/C, power steering, or smog pump changes it).
- Letting the tensioner snap back on your fingers.
- A belt sitting one rib off on a pulley.
- Ignoring a noisy pulley. A new belt won't fix a bad bearing.
Done check
- Belt follows the decal routing exactly.
- Every rib is in its groove on every pulley.
- Tensioner arm sits between its two index marks.
- No squeal, chirp, or flutter at idle or when revving.
- Battery light off, power steering normal, A/C works (if equipped).
Sources
Specs on this page come from factory service information, opened Oct 26, 2026. Where we could not find a sourced spec, we say so instead of guessing.
- Factory service information, 1993 Mustang 5.0L HO: Drive Belt Service and Repair (Operation CHARM)
- Factory service information, 1993 Mustang 5.0L HO: Drive Belt Adjustments, automatic tensioner (Operation CHARM)
- LMR: How To Replace A Serpentine Belt In A Mustang (tool tips)
Fitment sources: which years share the part
We have no parts-catalog fitment data for this job yet, so videos from other years are only labeled, never called a match.
We only match years inside the same body: the Fox-body Mustang ran 1979-1993 (source).
Video model years
- How To Change Mustang Serpentine Belt - LMR Basics: No model year in the title or description
- Whats the CORRECT way to route a fox body Mustang belt, and why?: No model year in the title or description