Tire preasure display- How does it work?

[Gary L]

Will try to be short if possible.

2003 Grand Ch. Limited has tire preasure readout inside the vehicle. I use the donut ring to reset when I rotate. It works fine and is quite accurate.

It is bitter cold, below zero and I am loosing air in all 5 tires.

I suspect the valve stems are the culprit and also suspect this could be quite expensive to fix.

I think the sensors are in the stems but really don't know how the signal gets from each wheel to the OBC display in the vehicle.

What I do know is the tires are fine but are loosing air when it gets very cold.

It is way too cold right now to try the sudds/bubble test to search for leaks.

Gary

[Steel]

how much air? If its stupifyingly cold outside, then there pressures will go down naturally as P=(nRT)/V. They could go down quite a few PSI. When you drive, they pressure will raise because the tires are heating up.

But, if you have a leak, it's probably in the tire itself and not the valve stem/sensor assembly. If it IS that assembly, its most likely the valve core, which are really cheap to get new ones.

[Gary L]

Thanks Steel, "Stupifyingly Cold"! I guess with wind chill figured in at -14 degrees this qualifies.
Sunday I aired up and had 35 PSI in all 5 tires. Today, wednesday I have betweens 23 and 29 in all 5.
I can't believe all 5 tires develope slow leaks and all at the same time, even the spare. Driving and warming does bring them back up some but only a couple of pounds. Where is this air going?

When you say the core, are you talking about the removable valve/spring gadget inside the stem?

I can easily replace these but wonder if I should dismount the tires and clean with some kind of tiny wire brush to do it right.
Is there an oil or grease I should apply?
I do live in the NY mountains where heavy road salting is the norm which destroys about everything on a car but I do keep caps on the stems.

Gary

[UncleBob]

the likelihood of 5 tires suddenly developing slow leaks at the same time is, to put it mildly, unlikely.

Temp changes can cause abnormally quicker pressure loss. Its quite normal.

The signal gets from the sensors in the tire to the computer via radio signals. There is no wires between the sensors and computer.

Some of the older setups didn't use sensors in the tires, but instead used the ABS wheel speed sensor and would count revolutions per mile and track wheel diameter, and thereby, inflation, but this system wasn't terribly popular, because the computer didn't know what the actual psi of the tire was, it only noticed a sudden loss of pressure. It also took a while to "relearn" after making changes, such as changing tire pressure or changing tires...or rotating tires.

[Gary L]

I am thinking there is some sort of sensor/transmitter built into the valve stems that sends the signal Via RF when the magnetic donut is applied.

Thats why I am worried because normally when I buy new tires I stipulate I want new valve stems installed. Not so easy with this set up and probably pretty expensive.

I agree, all 5 tires are not leaking but I suspect the valve stems need some attention, possibly just new valve/spring gadgets screwed in will do the trick.

I am deffinitly loosing air slow but sure.

Gary

[UncleBob]

as I said, accelerated pressure loss during a large temp change is quite common. I don't think there's anything wrong at all.

[Gary L]

Thank you Uncle Bob. I will keep an eye on this for safety sake and hope that your assumptions are correct.
It does however beg a question as to why my two other vehicles are not similarly affected and my only thoughts are the rubber compounds of the tires themselves maintain in severe conditions.

Gary

[Scrapper]

probably leaking around the rim if there all doing it..