Weird Tire Pressure Problem

Steve335i · 09-24-2008, 08:48 AM

Had the tpms go off yesterday. Checked all the tire pressures, both rear tires were down to 20 lbs.

Removed both rear wheels and used soapy water to find the leak(s). Didn't find any. Put the wheels in a tub of water, no leaks.

Aired the rears up to 45 psi and left them for 4 hours, maintained 45 psi. Lowered the pressure to 35 psi and left it overnight.

Checked in the morning and both rears are 35 psi. Drive 17 miles to work and about half way the tpms goes off again. Get to work and both rears are down to 20 lbs. again. WTF?

Perpetrator · 09-24-2008, 10:43 AM

Similar thing happened to me on 2 occasions. Turned out to be a leak from the TPMS unit itself. Cost me about $20 for a shop to install a rebuild kit (including the kit).

Steve335i · 09-24-2008, 11:56 AM

I was wondering about that. The tpms are probably less than a year old with about 3,000 miles.

slick101 · 09-24-2008, 04:03 PM

i had the same problem witht he front wheel... i had it checked out and turned out to be a tiny hole in the rim itself...i can barely see it..that's where the bubbles were comin out of....i dont know wut to do..?

Steve335i · 09-25-2008, 08:13 AM

Quote:

Originally Posted by Perpetrator

Similar thing happened to me on 2 occasions. Turned out to be a leak from the TPMS unit itself. Cost me about $20 for a shop to install a rebuild kit (including the kit).

My dealer is playing dumb, says they've never heard of a malfunctioning sensor causing a leak. You wouldn't happen to have a part number for the rebuild kit? The strange thing is the rear tires only lose pressure when driving, not sitting.

Perpetrator · 09-25-2008, 11:19 AM

Quote:

Originally Posted by Steve335i

My dealer is playing dumb, says they've never heard of a malfunctioning sensor causing a leak. You wouldn't happen to have a part number for the rebuild kit? The strange thing is the rear tires only lose pressure when driving, not sitting.

Don't know the part number. If you've never swapped out wheels, or have moved the TPMS yet, then they should still be fine. What happens is when you get aftermarket wheels, or move your sensors from one set to another, SOME shops will accidentally over-torque the sensor and cause a slight puncture/tear in one of the seals. They replaced just that one part, not the entire sensor. If the dealer can't figure it out, then take your car to a large retail tire shop that does free leak repair/patch. In my case, I went to America's Tire/Discount Tire. The dealers probably don't handle too many tire issues, so they may not be familiar with possible causes. Besides, tire shops would be better able to analyze tire issues, than a car dealership.

Let us know what it turns out to be! Of course, your issue may be something completely different. Good luck.

Steve335i · 09-25-2008, 12:14 PM

Thanks Perp...I took the car to a Goodyear shop, the ones who installed the aftermarket wheels. I installed the new tpms sensors on the wheels and they've been working fine for the last 3 months and still do give the warning when the tire pressure drops. No problem with the fronts and I find it significant that both rear wheels started losing pressure at the same time. The tire shop couldn't find any leak and neither could I. I guess I'll remove 2 sensors from the OE wheels and swap them out to see if it makes any difference.

Perpetrator · 09-25-2008, 12:45 PM

No problem.

Just as a reference....I had my aftermarket wheels on for about 1K miles before this happened with my front wheel. After fixing it, I had the other front wheel do the same about 2 weeks later. Both cases were the TPMS leaking. Ask the shop to check the grommet (or maybe it's called something else) on your TPMS, and see if they think it may be leaking.

I'm hoping that yours will be a simple $20 fix like mine was, and nothing worse.

Steve335i · 09-29-2008, 10:48 AM

Doh! Checked the nut on the valve stems and both rears were loose. The centrifugal force of the rotating tire was pulling the sensor off the wheel, allowing a leak around the rubber gasket on the valve stem inside the wheel. This is why the rear tires only lost pressure while driving. Thanks to Perpetrator for pointing me in the right direction!

09-24-2008, 08:48 AM	#1
Steve335i Private First Class 4 Rep 111 Posts Drives: 335is Join Date: Oct 2007 Location: Tampa Bay iTrader: (0)	Weird Tire Pressure Problem Had the tpms go off yesterday. Checked all the tire pressures, both rear tires were down to 20 lbs. Removed both rear wheels and used soapy water to find the leak(s). Didn't find any. Put the wheels in a tub of water, no leaks. Aired the rears up to 45 psi and left them for 4 hours, maintained 45 psi. Lowered the pressure to 35 psi and left it overnight. Checked in the morning and both rears are 35 psi. Drive 17 miles to work and about half way the tpms goes off again. Get to work and both rears are down to 20 lbs. again. WTF?
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09-24-2008, 10:43 AM	#2
Perpetrator Lieutenant 21 Rep 407 Posts Drives: E90 330i Join Date: Dec 2007 Location: Fullerton, CA iTrader: (4)	Similar thing happened to me on 2 occasions. Turned out to be a leak from the TPMS unit itself. Cost me about $20 for a shop to install a rebuild kit (including the kit).
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09-24-2008, 11:56 AM	#3
Steve335i Private First Class 4 Rep 111 Posts Drives: 335is Join Date: Oct 2007 Location: Tampa Bay iTrader: (0)	I was wondering about that. The tpms are probably less than a year old with about 3,000 miles.
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09-24-2008, 04:03 PM	#4
slick101 Lieutenant 47 Rep 558 Posts Drives: 07 335i coupe Join Date: Jan 2007 Location: ny iTrader: (1) Garage List 2007 E92 335i [0.00]	i had the same problem witht he front wheel... i had it checked out and turned out to be a tiny hole in the rim itself...i can barely see it..that's where the bubbles were comin out of....i dont know wut to do..? __________________
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09-25-2008, 12:14 PM	#7
Steve335i Private First Class 4 Rep 111 Posts Drives: 335is Join Date: Oct 2007 Location: Tampa Bay iTrader: (0)	Thanks Perp...I took the car to a Goodyear shop, the ones who installed the aftermarket wheels. I installed the new tpms sensors on the wheels and they've been working fine for the last 3 months and still do give the warning when the tire pressure drops. No problem with the fronts and I find it significant that both rear wheels started losing pressure at the same time. The tire shop couldn't find any leak and neither could I. I guess I'll remove 2 sensors from the OE wheels and swap them out to see if it makes any difference.
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09-25-2008, 12:45 PM	#8
Perpetrator Lieutenant 21 Rep 407 Posts Drives: E90 330i Join Date: Dec 2007 Location: Fullerton, CA iTrader: (4)	No problem. Just as a reference....I had my aftermarket wheels on for about 1K miles before this happened with my front wheel. After fixing it, I had the other front wheel do the same about 2 weeks later. Both cases were the TPMS leaking. Ask the shop to check the grommet (or maybe it's called something else) on your TPMS, and see if they think it may be leaking. I'm hoping that yours will be a simple $20 fix like mine was, and nothing worse.
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09-29-2008, 10:48 AM	#9
Steve335i Private First Class 4 Rep 111 Posts Drives: 335is Join Date: Oct 2007 Location: Tampa Bay iTrader: (0)	Doh! Checked the nut on the valve stems and both rears were loose. The centrifugal force of the rotating tire was pulling the sensor off the wheel, allowing a leak around the rubber gasket on the valve stem inside the wheel. This is why the rear tires only lost pressure while driving. Thanks to Perpetrator for pointing me in the right direction!
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