fixerupper
Well-known Member
My turn for the stupid question of the month; does the cap need to be on a tire valve stem for the low tire sensor on a newer vehicle to work right? Will elaborate later.
- Thread starter fixerupper
- Start date
Billy Shafer
Well-known Member
Did you lose the cap. I really see no reason for it,just a cover to keep the dirt out
Larry EC-OH
Member
Well a quick check on google says there are about 4 different systems.
The caps look different, but nothing I read indicated that they are a necessary requirement.
Hope this helps,
Larry
The caps look different, but nothing I read indicated that they are a necessary requirement.
Hope this helps,
Larry
fixerupper
Well-known Member
The cap was off. 09 Chevy Colorado. The warning light came on way back last August when I was 150 miles away from home. I got out, looked at the tires and they looked OK. When I got home I checked the pressures and they were all equal at 33 LBS but a cap was off the right rear and I didn't happen to have one in my pocket so I took off without a cap on the valve stem. I have checked the tires several times since then, the light has been on ever since and they were all equal, but I didn't have a cap when I checked them so it was ignored. I finally put a cap on today when I serviced the pickup. One tire , the one without the cap, was ten pounds lower than the rest so I pumped it up and equalized all tires at 34 LBS. Now the light is off. Coincidence?
All I know is be sure to check the spare tire.
On my car, the donut spare also has the sensor. Being that the spare carries 60 psi it looses pressure faster than
all the rest, and it triggers the light soonest. Seems even if it is as low as 54 psi it will turn the light on.
After pumping up, sometimes takes up to 40 miles, or 4-5 starts for the sensor to reset itself.
On my car, the donut spare also has the sensor. Being that the spare carries 60 psi it looses pressure faster than
all the rest, and it triggers the light soonest. Seems even if it is as low as 54 psi it will turn the light on.
After pumping up, sometimes takes up to 40 miles, or 4-5 starts for the sensor to reset itself.
Larry EC-OH
Member
It may be coincidence. I know on mine I have to have at least 35 lbs of pressure to get the light to turn off. It can then go down to 33 pounds before I get the warning. You may have been a fraction of a pound low (thus the light) and when you added a little air it may have been enough to turn the light off.
Then again it might be due to global warming, gremlins, etc.
Larry
Then again it might be due to global warming, gremlins, etc.
Larry
ditchwitch
Well-known Member
the valve stem is part of the sensor . you just see the valve stem from outside the sensor is inside the rim
ditchwitch
Well-known Member
the answer is no, the cap is for protection helps keep stuff from getting into stem small gravel
sand mud anything small enough to hit stem and let air out
sand mud anything small enough to hit stem and let air out
farmerwithmutt
Well-known Member
I used to pick up milk samples on farm one farmer had a huge saint Bernard this dog could bite a tire and flatten it. One cold day he came up to sprinkle his blessing on my tire the valve stem got froze down ever since i make sure i got caps on tires.
Nothings ever the same. They are fastened to the bottom of the valve stem inside the tire, little rectangle plastic piece maybe 1/4" thick, valve stem cap is a good idea to keep crap out but think the sensor should work fine without. I remember working on one car, maybe a little Ford, that the sensors were held to the inside center of the rim with a steel band. When the system works it's a good idea, when it's got a problem it could be as simple as a sensor or a real pain in azz.
ditchwitch
Well-known Member
if your just replacing a tire your ok. They just have to be carefull not to damage the sensor with there tire machine when removing the tire. And yes i dont think you can buy a generic sensor (yet) it has to be for your brand car. Sometimes you they also are in different megahertz and frequency because all that has to do with the module thats in car.
Dune Country
Well-known Member
I have always been told that the a tire stem has 2 seals, the core and the cap, they do have rubber inside.
There are a few "generic" replacement sensors available. Each manufacturer has their own specifics, some manufacturers have changed design several times already. As someone mentioned, Ford originally had sensors banded to the rim, but now use valve mounted ones.
In the near future we will hear more about failed sensors. The design life of the early ones was only 5 years, and we are now 9-10 years out. The newer systems are supposed to last 10 years.
Some of the car manufacturers (IE Chrysler) have made the system easy where you can just replace a faulty sensor and the vehicle will relearn the new one by itself. Others you need to go through a relearn sequence. And then most of the Asian manufacturers you have to go into the factory programming to get a different sensor to work. (A programmable generic sensor can get you around that.)
As to the valve cap, yes they are a secondary seal, but I would not count on a plastic cap holding any pressure. No the missing cap would not have affected your warning light.
In the near future we will hear more about failed sensors. The design life of the early ones was only 5 years, and we are now 9-10 years out. The newer systems are supposed to last 10 years.
Some of the car manufacturers (IE Chrysler) have made the system easy where you can just replace a faulty sensor and the vehicle will relearn the new one by itself. Others you need to go through a relearn sequence. And then most of the Asian manufacturers you have to go into the factory programming to get a different sensor to work. (A programmable generic sensor can get you around that.)
As to the valve cap, yes they are a secondary seal, but I would not count on a plastic cap holding any pressure. No the missing cap would not have affected your warning light.
Many of these systems fail after several years, sensors go bad, go dead etc. There are enough different systems out there its too hard to keep up with each one and how to program them. It's also expensive to have the equipment to diagnose and train sensors, and the sensors themselves are expensive to buy.
The best system out there IMO is the indirect system, it doesn't use sensors in the tires, instead it uses the ABS sensors and measures wheel speed difference. This system is smart enough to know when you rotated tires or one is a few pounds lower than others. There is a simple button on the dash or button sequence in the message center to re-calibrate the system. The down side is it does not directly measure tire pressures, and can not tell you which one is low, which to me is not that big of deal
The best system out there IMO is the indirect system, it doesn't use sensors in the tires, instead it uses the ABS sensors and measures wheel speed difference. This system is smart enough to know when you rotated tires or one is a few pounds lower than others. There is a simple button on the dash or button sequence in the message center to re-calibrate the system. The down side is it does not directly measure tire pressures, and can not tell you which one is low, which to me is not that big of deal
fixerupper
Well-known Member
Looks like I will have to run a couple more pounds pressure. Thanks for the hints.
A couple years ago I made a rookie mistake and ripped off a sensor with the tire changer. I won't do that again. The new sensor was in the $100 area.
A couple years ago I made a rookie mistake and ripped off a sensor with the tire changer. I won't do that again. The new sensor was in the $100 area.
General rule of thumb is for every 10 degrees of temp change, the tire pressure will change about 1 lb. Lower temp = lower pressure, higher temp = higher pressure If your tires are near the lower threshold of tripping the light on a warmer day and a cold front moves in then the low tire might come on due to losing a couple psi. This is one of the small benefits to using nitrogen for fill, its not affected by temp change, or at least its very very slight.
Sean Feeney
Well-known Member
I agree Tom Brady
There is a switch that is weighted and switches on when the tire rotates. When the switch is closed, it transmits the air pressure to one of the cpus in the car. 2007 Colorado I drive for work is on its third set of sensors in 255,000 miles. This system just has a one light saying which tire is low. Newer systems indicate which tire. There are people out there yet that will still ruin a rim because the tire is gone because they don't look at the dash.
K Effective
Well-known Member
I must have forgotten that part of the Ideal Gas Law, PV=nRT, except for Nitrogen.
Seems I remember that those tire pressure sensors are the result of a federal mandate. True or false? Something about keeping tire
pressures at "normal" to help increase gas mileage?
By the way I hate those stupid things! Can't anyone remember automobile maintenance anymore? Has common sense gone away completely?
pressures at "normal" to help increase gas mileage?
By the way I hate those stupid things! Can't anyone remember automobile maintenance anymore? Has common sense gone away completely?
Seems I remember that those tire pressure sensors are the result of a federal mandate. True or false? Something about keeping tire
pressures at "normal" to help increase gas mileage?
By the way I hate those stupid things! Can't anyone remember automobile maintenance anymore? Has common sense gone away completely?
pressures at "normal" to help increase gas mileage?
By the way I hate those stupid things! Can't anyone remember automobile maintenance anymore? Has common sense gone away completely?
fixerupper
Well-known Member
Today I asked this question to a tire guy. He said it doesn't matter if the cap is off or on but if the cap is off the junk that gets in there can make the sensor do 'funny things'. Our Toyota van has a bad sensor. It's nine years old with 150,000 miles so I thought about having all four replaced just to get it over with. The car repair place I go to quoted me a twitch over $800! I'm replacing only the bad one. He said some of the import cars have a sensor with a serial number that has to be programmed into the car computer. This car repair place is a little higher priced but they are good at what they do.
BarnyardEngineering
Well-known Member
- Location
- Rochester, NY
The solution could be much simpler:
If you were using one of those "stick" type pressure gauges that doesn't retract automatically, all four tires will read EXACTLY what the first tire read, unless they have higher pressure.
Doesn't the dash display on your vehicle show you the pressures? I haven't driven a vehicle with TPMS yet that didn't have the option of displaying the current tire pressures on the dash. You have to cycle through a few screens to do it.
If you were using one of those "stick" type pressure gauges that doesn't retract automatically, all four tires will read EXACTLY what the first tire read, unless they have higher pressure.
Doesn't the dash display on your vehicle show you the pressures? I haven't driven a vehicle with TPMS yet that didn't have the option of displaying the current tire pressures on the dash. You have to cycle through a few screens to do it.
fixerupper
Well-known Member
quote]
I'll have to thumb through the manual for this pickup to see if I can cough up the tire pressures on the readout. This pickup is fairly basic when it comes to options.
When I use a stick gauge I do push the stick back in every time. I usually use a dial gauge but someone damaged it rendering it useless so the stick gauge came in handy.[/quote]
Hobo,NC
Well-known Member
- Location
- Sanford, NC
I could be wrong but I have not ran into one I could not clone and program into the system. I would check another place :wink: That's one reason I use programmable sensors before that I had to use a scan tool and enter the serial number on the new sensor into the OBD2 connector on Asian vehicles. Then go thru a P.I.T.A. relearn :evil:
There are four different types in use today that fit 98% of the vehicles out there.
2- Snap in, in two different MHz 315 & 413
2- Clamp in, in two different MHz 315 & 413
It pays to install a service kit when you replace the tires on the snap-in install/add a new valve stem. I get most of my repairs from vehicles that come in with the TPMS light on the customer has learned to live with it. I do a free check (to enhance my knowledge of these systems) it would supersize folks to know most shops know little about this system and shrug it off are run you away from repairing it with BIG prices. .
It was a learning curve that was hard as chines rifmytic. Once a person gets comfortable with it and answers all the un-told questions its quite EZ other than getting over the expense of the tools needed to work on them. I have invested about 2K dedicated to test/relearn/program so YES I push it.
Anyone that is comfortable diagnosing OBD2 issues will be more than comfortable diagnosing TPMS its a money maker and plenty of it is headed your way.
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