Auto Parts Ordering Checklist: 6 Things I Verify Before Every Order

I'm the office administrator for a 12-person auto repair shop. Parts purchasing is my responsibility—roughly $80,000 a year across 10 different suppliers. I report to the shop manager and the owner, though honestly I answer to the head tech when a part's late.

If you're the one who orders engine or drivetrain parts for a shop, fleet, or machine shop, this checklist is for you. It's six things I run through before hitting order, built from way too many years of trial and error. Nothing here is complicated. It's just a series of checks that keep a job from stalling on the lift.

1. Measure the part when length or fitment matters

This sounds obvious, but it's hands-down the most common mistake I see in our shop. People trust the database, they trust the VIN, they trust the parts store's "yeah, that'll fit." Then the part shows up and it's 3 inches short.

Take a driveshaft, for example. How to measure a driveshaft isn't just running a tape from flange to flange. You measure the center-to-center distance between the u-joint cups, not the overall tube length. You also need the tube diameter at the widest point, the number of splines on the slip yoke, and the flange type (1310, 1330, 1350, etc.). If it's a two-piece shaft, measure each section separately and note the center support bearing location.

One more detail that gets overlooked: the measurement changes depending on whether the suspension is loaded or hanging. A lifted truck with the axle drooping reads different than one sitting on level ground. I learned that one the hard way.

Before I order a driveshaft, I have the tech physically look at the vehicle. Driveshafts are often built to order, and a return means the car occupies a bay for another week.

2. Verify what the "kit" actually contains

Not all kits are created equal. A timing belt kit might be just the belt. It might be a belt with a tensioner. Or it might include a water pump. "Kit" is a loose word in this industry.

The Dayco WP286K1C timing belt kit with water pump is one that does include the pump—it's right in the name. But I've still learned to open the box and verify. I've seen repackaged kits missing the tensioner. I've seen distributors swap in a different brand's water pump. If a kit says "with water pump," I expect the belt, the water pump, the tensioner, and the idler pulley all in that box. If something's missing before you open it, that's on the supplier. If you notice after the old parts are off the car, that's on you.

Also pay attention to engine coverage. The same kit number doesn't always fit every engine that "looks the same." Dayco's catalog lists exact engine codes—use it. If a VIN isn't matching, stop and check before we order a second kit.

3. Don't skip the pulleys—this is the one people push back on

This is the advice that gets the most resistance. "The old pulley spins fine, just reuse it." I've heard it from mechanics and shop owners alike. And every shop I know has a comeback story that started with a reused idler pulley.

If the timing belt kit is already in your hand, the idler pulley is right there. On many engines, getting to it later means removing the belt tension, the bracket, and half the accessory drive again. Replacing it now costs a few extra dollars. Replacing it later costs labor—and a customer who's not happy.

A good example is the Dayco 89144 idler pulley. That's a popular part number we order regularly. It's a common failure point. The bearing dries out, starts making noise, and if it seizes, it takes the belt with it. If I'm putting in a timing belt kit, the idler pulley gets replaced at the same time. It just does.

It took me maybe 3 years and 25 timing jobs to fully get on board with this. At first I ordered belt-only kits to save the customer money. Now I quote the full kit with water pump and pulleys every time. Same logic as replacing the thermostat when you do a water pump—it's already opened up.

4. Cover the AC condenser before any front-end work

This wasn't on my radar until a customer came back with no A/C a few weeks after a timing belt replacement. Coincidence? Not really.

When you're doing a timing belt, water pump, or radiator, debris falls. Tools fall. Brackets drop. And the AC condenser sits right there in the front, with thin aluminum fins that dent if you look at them wrong. So please—cover the AC condenser before the job starts.

A heavy rag or a piece of cardboard over the condenser takes four seconds. Some vehicles even have factory plastic protective covers, but mechanics usually toss them during previous repairs. If enough fins get crushed, airflow drops, the A/C won't cool properly, and the customer's looking at a condenser replacement that isn't cheap on any car.

I put "protect condenser" as a line item on our estimates. It's not a charge—it's a note to the tech and a signal to the customer that we're careful with their vehicle.

5. Inspect the crankshaft before you install the new parts

If the timing belt snapped while the engine was running, or oil was leaking from the front main seal, don't just install the new kit. Check the crankshaft first.

What I'm referring to is crankshaft polishing—the process of removing minor scoring, rust, and small burrs from the crankshaft journals. It's done with a fine abrasive belt or stone, and it restores the journal surface so new seals and bearings won't get chewed up. It's one of those services nobody lists on a menu, but it saves an engine from coming back apart.

Here's what I ask the tech to check when the timing cover is off:

• Front seal surface—any groove or wear means the new seal won't hold.
• Journal surfaces—scoring or rust spots on the rod and main journals.
• Crankshaft end float—excessive movement can mean a worn thrust bearing.

If the crank has a deep groove where the old seal was sitting, polishing won't fix it. That shaft has to come out, and it's a machining conversation. But for shallow surface issues, a proper polish job in place is enough to seat a new seal and keep the engine dry for another 100,000 miles.

To be fair, most timing belt failures don't damage the crankshaft. But the ones that do don't advertise themselves. You have to look.

6. Keep records that would survive an audit

This is the unglamorous step that saves us the most time. I process 60–80 orders a month across multiple suppliers. If I didn't track them, returns and warranty claims alone would eat an entire day each week.

For every order I record the date, the part number, the vehicle, the VIN, the mileage, and a photo of the part before it goes into the box. That's it. Nobody asked me to start doing this. It's just become our system, and it's the reason we've won two warranty disputes where suppliers tried to claim they never sold us the part.

There's something satisfying about a clean order trail. When a tech comes back two months later with a leaking water pump and I can pull up the invoice and photo in thirty seconds—that's efficiency. I don't have to call the distributor and go back and forth. I have the proof on hand.

It's tempting to think you can just rely on the supplier's purchase history. But when you're dealing with 10 vendors, each with their own system, none of them care about your records as much as you do. That recordkeeping is what separates a smooth operation from an endless series of "who's responsible for this?" meetings.

What to do when something still goes wrong

This checklist has cut our job-stalling returns from four or five a month down to maybe one. But things still slip through. When they do:

• Don't force a part. If the new pulley doesn't spin freely or the belt doesn't line up, stop. Call the supplier before the problem gets worse.
• Photograph the old part. Write down the original part number from the old unit. We've caught wrong-application claims this way.
• Ask about warranty and return policy before ordering, not after. Some distributors restock within 30 days, some don't.
• If the job touched the crankshaft, note the seal condition in the work order. It costs nothing and saves a lot of guesswork later.

So glad I stopped letting suppliers tell me "should be fine" and started verifying things myself. Almost cost us a regular customer early on when a supposedly fine driveshaft came up short by three inches. Now we measure, we check, we document. And that's the whole system.