97 F250HD 4x4 5.8L 351W E4OD - Smog Pump Ticking Sound

Hey Everyone!

I’ve been listening to Car Talk for as long as I can remember and my mechanic and I hit our first “puzzler” today. My first thought was, “Man, if only I could call Tom and Ray!” Then I thought to myself, “Wait a second, there’s a forum on the Car Talk website!” Hopefully you all can help!

I am the second owner of my truck–both the first owner and I have maintained it meticulously and promptly serviced anything that needs to be maintained. With that said, the truck does have 260,000 on the original motor and transmission–but it drives and shifts like a dream!

I just had an engine tune up (spark plugs & wires/distributor cap & rotor), oil change, transmission/transfer case service, and replaced the upper and lower radiator hoses. Other than that, in the last 15,000 miles the truck has gotten a new water pump, coolant flush, serpentine belt and tensioner, 02 sensor, engine thermostat, air & fuel filter, timing chain gasket, new battery, new brakes all around, alignment and new suspension all around (front and rear springs and shocks).

When I took the truck into my mechanic for the serp belt & tensioner, I asked him about a ticking noise coming from the passenger side. He confirmed (with agreement from two other techs) with his stethoscope that is was coming from the smog pump. He ordered a new (well, not brand new since they don’t make them anymore, but rebuilt/refurbished) smog pump from either Napa or Baxter and just installed it today. To both his and my dismay, the ticking noise did not go away–in fact, we think it got a little louder?

He had a few theories:

  • Since it is a ‘rebuilt’ smog pump, it could have not been refurbished adequately and it could have the same issue my old one has.
  • The ‘ticking’ sound could be caused by a clogged line connected to the smog pump
  • It could be related to the catalytic converter being old

First, I don’t for a second think or worry that my mechanic is just trying to get more money out of me–I know him personally and he’s a good guy and a good mechanic. He was arguably more bummed/annoyed about the sound not going away than me, cause he’s not charging me for something he encouraged me to do that wasn’t fixed.

When I asked him if he was 100% sure it is coming from the smog pump, he said, “The stethoscope confirms it (along with two of his techs) and when we detach the serpentine belt from the smog pump, the noise stops.”

So we are both scratching our heads a bit. Regarding the next steps, he wants me to drive it for a week and see if anything changes (he’s out of town), and if it doesn’t resolve itself, here are our options:

  • Order another smog pump to see if this one is defective
  • Put the old pump back on and try to investigate/chase down a clogged/restricted line (trying to avoid this)
  • Test the catalytic converter for back pressure
  • Delete the smog pump, which is pretty common by using a dummy pulley and keeping the same length serpentine belt. Ideally I want to avoid this (unless someone here has a strong opinion otherwise) because I believe in keeping things as stock as possible. If I deleted the smog pump, I would likely still pass the sniffer emissions test, but I’ve also heard that it’s better for the cats and cold idle to have to smog pump.

Okay…sorry for a pretty long first post, but I wanted to make sure I gave as much info as I could to help maybe diagnose this.

Any thoughts? Questions? Concerns? Remedies?

Thank’s in advance Car Talk Community!


Was the air pump check valve tested?


1 Like

Hey Tester,

I’m not sure–I will ask when I take the truck in next week. Is this part of the smog pump or a separate component?


The air pump will have rubber hose to the check valve, which is attached to a steel tube to the exhaust system.


Got it–thanks!