phantom tire pressure loss HELLLP!
Thread Starter
Racer
Joined: May 2006
Posts: 376
Likes: 0
From: Suburbs of New Orleans La
phantom tire pressure loss HELLLP!
About 500 miles ago I installed Michelin Pilot Sport PS2 ZP's on my C6.
Since then, whenever the car is driven at highway speeds (65-70+) the left front loses air. It can sit for a week and not lose an ounce, and if you are in normal surface street traffic, it does not lose pressure.
Last Thursday I drove home from work after having it remounted and checked for bead irregulaities, as well as inspection of the valve stem assembly.
The tires were at 35PSI hot when I got on I-10, and when I got off 15 or so miles later, the haunted tire was down to 28. I brought it back up to 35 hot to match the other tires, drove the rest of the way home and parked the car.
When I got in this morning it was at 32 cold, just like the others. As I drove around and the tire heated up it rose to 34. I got on the highway, and by the time I got to work it was down to 29 hot while the rest are at 34 or 35.
I broke the tire back down again this morning and I and two other people including an ASE master tech inspected the tire again. The rim is perfect, and I never had any problem in the previous 17K miles on the Goodyears.
Do I need to call an exorcist?
Since then, whenever the car is driven at highway speeds (65-70+) the left front loses air. It can sit for a week and not lose an ounce, and if you are in normal surface street traffic, it does not lose pressure.
Last Thursday I drove home from work after having it remounted and checked for bead irregulaities, as well as inspection of the valve stem assembly.
The tires were at 35PSI hot when I got on I-10, and when I got off 15 or so miles later, the haunted tire was down to 28. I brought it back up to 35 hot to match the other tires, drove the rest of the way home and parked the car.
When I got in this morning it was at 32 cold, just like the others. As I drove around and the tire heated up it rose to 34. I got on the highway, and by the time I got to work it was down to 29 hot while the rest are at 34 or 35.
I broke the tire back down again this morning and I and two other people including an ASE master tech inspected the tire again. The rim is perfect, and I never had any problem in the previous 17K miles on the Goodyears.
Do I need to call an exorcist?
Team Owner
Joined: Feb 2000
Posts: 53,516
Likes: 77
From: Arizona
About 500 miles ago I installed Michelin Pilot Sport PS2 ZP's on my C6.
Since then, whenever the car is driven at highway speeds (65-70+) the left front loses air. It can sit for a week and not lose an ounce, and if you are in normal surface street traffic, it does not lose pressure.
Last Thursday I drove home from work after having it remounted and checked for bead irregulaities, as well as inspection of the valve stem assembly.
The tires were at 35PSI hot when I got on I-10, and when I got off 15 or so miles later, the haunted tire was down to 28. I brought it back up to 35 hot to match the other tires, drove the rest of the way home and parked the car.
When I got in this morning it was at 32 cold, just like the others. As I drove around and the tire heated up it rose to 34. I got on the highway, and by the time I got to work it was down to 29 hot while the rest are at 34 or 35.
I broke the tire back down again this morning and I and two other people including an ASE master tech inspected the tire again. The rim is perfect, and I never had any problem in the previous 17K miles on the Goodyears.
Do I need to call an exorcist?
Since then, whenever the car is driven at highway speeds (65-70+) the left front loses air. It can sit for a week and not lose an ounce, and if you are in normal surface street traffic, it does not lose pressure.
Last Thursday I drove home from work after having it remounted and checked for bead irregulaities, as well as inspection of the valve stem assembly.
The tires were at 35PSI hot when I got on I-10, and when I got off 15 or so miles later, the haunted tire was down to 28. I brought it back up to 35 hot to match the other tires, drove the rest of the way home and parked the car.
When I got in this morning it was at 32 cold, just like the others. As I drove around and the tire heated up it rose to 34. I got on the highway, and by the time I got to work it was down to 29 hot while the rest are at 34 or 35.
I broke the tire back down again this morning and I and two other people including an ASE master tech inspected the tire again. The rim is perfect, and I never had any problem in the previous 17K miles on the Goodyears.
Do I need to call an exorcist?
Maybe the tire sensor is bad.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
My money is on the "O" ring that seals the sensor for Low Tire Pressure Warning System (or LTPWS) to the rim.
Spray a little soapy water where the valve stem and rim meet. It may be fine sitting still but it may leak when wiggle it a little. Watch for bubbles to appear over 5-10 minutes. The valve stem "O" ring is very easy to damage if you try to tighten it too much or have it too loose. I actually broke the stem of the LTPWS sensor clean off just trying to get it to stop leaking.
If it is loose, just tighten it a little. I don't recall the exact torque specs, but its really low....something like 18 in/lbs. Anything more, you can damage the rim where the "O" ring seats. Be gentle here.
If you still can't stop it from leaking, you will have to remove the tire and replace the "O" ring. Inspect the hole in the rim as any damage to the seat will cause it to leak. Its a special part you have to buy from the GM dealer...its kind of a square notched looking thing so forget trying to get one at Autozone.
Below is a photo of the whole sensor including the nut. The black thing in the middle is the 'o' ring.
Good luck.
Spray a little soapy water where the valve stem and rim meet. It may be fine sitting still but it may leak when wiggle it a little. Watch for bubbles to appear over 5-10 minutes. The valve stem "O" ring is very easy to damage if you try to tighten it too much or have it too loose. I actually broke the stem of the LTPWS sensor clean off just trying to get it to stop leaking.
If it is loose, just tighten it a little. I don't recall the exact torque specs, but its really low....something like 18 in/lbs. Anything more, you can damage the rim where the "O" ring seats. Be gentle here.
If you still can't stop it from leaking, you will have to remove the tire and replace the "O" ring. Inspect the hole in the rim as any damage to the seat will cause it to leak. Its a special part you have to buy from the GM dealer...its kind of a square notched looking thing so forget trying to get one at Autozone.
Below is a photo of the whole sensor including the nut. The black thing in the middle is the 'o' ring.
Good luck.
Last edited by Mez; Apr 15, 2010 at 08:00 PM.
Race Director
Joined: May 2007
Posts: 10,805
Likes: 706
From: Feverish All Over
I replaced the "O" rings on my C6 TPS's with slightly "fatter" versions because I think the OEM versions are too thin - it is very easy to tighten the TPS nut and seat the valve to the rim and still not have an air-tight seal. The slightly fatter O ring helps guard against this.
I just took a TPS to my auto parts store and we rummaged thru his O ring display to find an O ring that was of the same diameter as the OEM's, but slightly "fatter". They fit perfectly....
I just took a TPS to my auto parts store and we rummaged thru his O ring display to find an O ring that was of the same diameter as the OEM's, but slightly "fatter". They fit perfectly....
Team Owner
Joined: Jun 2005
Posts: 46,295
Likes: 2,596
From: Northern, VA
St. Jude Donor '15
"In honor of jpee"
Mez is right and there is such a thing as over-tightening which can cause a leak. I have the same tires as of a month ago, and no leaks. I've also read about the caps themselves being over-tightened, but no confirmation on that causing a leak. Firm but gentle is the operative phrase for these TPMS, rings and caps.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
I was lucky. One of the holes in the rim where the 'O' ring seats was damaged probably by me over tightening the nut trying to get it to seal. I broke the LTPWS sensor so had to buy a new one. The new sensor came with a new 'O' ring so I had Discount install it very gently and it sealed! Whew! I thought I would have to get a reamer to fix the rim.
A few months later, it started to leak again. Oh, great, here we go again. I tightened the nut about 1/4 turn an it stopped leaking. Whew! I dodged the bullet again!
A little dish washing liquid mixed with water in a spray bottle will help you find the leak.
A few months later, it started to leak again. Oh, great, here we go again. I tightened the nut about 1/4 turn an it stopped leaking. Whew! I dodged the bullet again!
A little dish washing liquid mixed with water in a spray bottle will help you find the leak.
