Slow Leak in Both Rear Tires

[oskar27]

With 18K kilometer in my truck, this is the second summer I used my 18” original tires. Since up here we change the summer tires to snow tires for the winter period, I would say that the summer tires have about 10K kilometers.

About 4 weeks ago while I was driving, the low pressure tires warning came on and stopping at the nearest service station I noticed both rear tires were 28psi. So I pumped some air and forgot about them.

Yesterday while driving again the same warning came on and now I started to worry. Measuring again the tires pressure, both rear tires had again 28psi. The front have always been ok.

Next month I have to change my summer tires to snow tires and then I will take them for inspection. I find it very unlikely both rear tires to have a nail or something and I wonder if anyone here had a similar problem

[WWWPerfA_ZN0W]

Either the bead is weak, or there is rust along the edges of the wheel, or the valve stems themselves are leaking. You could always do the old soap & water test, but if it's a slow leak, may or may not work.

[oskar27]

The ideas are good but I wonder why they occurred after 1.5 years. Anyway I switch to the snow tires the second week of December and if I can't find any leaks I will take them out for service

[vrdublu]

I had the same thing happen but I found that one of my wheels was actually cracked on the inside lip. There was no impact damage visible to the eye at all.

[oskar27]

That must have been expensive! I hope mine will not be tha same

[vrdublu]

$170 to weld it back up with lifetime warranty. Could have been a lot worse I suppose.

[oskar27]

Just switched to winter tires tonight and noticed that the 2 front tires were 30Lbs. I'm not in the habit checking the air pressure in my tires and the only time I do so is when I change tires in April and December and I never had a problem before

This means to me that all 4 summer tires (the original) loosing air and now I find it very unlikely that there is something wrong with the tires.

I don't know how the tire pressure monitoring system works but I wonder if its possible this system to be the reason. Does anyone has an idea?

[Duckkarl]

One thing that people do not realize is that tires lose pressure on there own. It is common for tires to lose about 2.5 psi per month. Tires can also lose about 2 psi for every 10 degree drop in temperature. These figures are average numbers, and your change will vary. The reason tires lose pressure with temperature has to do with the moisture in air. That is why high performance applications like racing tend to use nitrogen in their tires, because nitrogen has no moisture in it.

 

That being said, I find it unlikely that both rear tires have an issue, but the mechanic in me would definitely do some further investigation. I would adjust the pressure using a known good pressure gauge. I would then use a soapy water solution on the valve stem, the side walls, tread and beads. Take your time, and use lots of soapy water. Any bubbling could be a leak. If no leak is found, let the tires sit, and recheck pressure after a week to see what you have.

[akirby]

Just checked all my tires and they were all at 26 lbs. they will lose air on their own and especially with cold weather.

[oskar27]

I agree with what you guys say and it is a common logic but based on my experience I have a different view. Yes the tires pressure will fluctuate with the ambient temperature and driving conditions but when the car sits inside a heated garage the next morning the tires pressure will always be the same unless there is a leak. This is based on my personal experience with the two Passats I had in the last 15 years; I never checked the tires pressure and never had a single problem with them

With my current Edge, since I bought her in February 2013 I never checked the tires pressure except recently when I got the low air pressure warning light ON and I discover that there is a problem with my 2 rear tires and I started this thread

With the above I'm just expressing my own experience and I don't deny what you said is the right thing to do but some times when we are busy, we just don't have the time to check tires pressure.

I will do the test with a soapy water solution but I doubt I will find anything and then I will ask the dealer to see if they know anything about my problem

[macbwt]

It could have been a bad mould pouring process and the aluminium is porus due to air contamnation, which could result in leakage. This would of course be difficult to discover as it would involve the destruction of the wheels.

[omar302]

When changing tires, did you change the valve stems? They might be faulty.

[oskar27]

The car came with the 18” wheels/tires and at the same time I ordered the 17” winter wheels/tires. I never changed the valve stems. The strange part is that in the summer of 2013, that is the 1^st summer I used the car, I never had a problem and never checked the tires pressure which to me means there is no manufacturers default with the wheels/tires

[akirby]

 

in the summer of 2013, that is the 1^st summer I used the car, I never had a problem and never checked the tires pressure which to me means there is no manufacturers default with the wheels/tires

 

 

That is a terrible assumption. If you never checked the pressure how do you know they weren't leaking? They have to be down 25% before the TPMS warning comes on, which is about 9 lbs low. Maybe they were 8 lbs low last year.

 

And problems can develop over time. With the faulty valve stems they didn't fail right away - took months or years.

 

You really just need to fill them back up and monitor them closely to see if they're slowly leaking.

[oskar27]

As I explained before I have the habit (perhaps a bad one?) not to check tires pressure and never had a problem with any tire. I'm retired now which means that is a long way I have been doing that and it has been successful.

It is true that I never had before a CUV which has BIG tires and perhaps I should change my habit at least for now to resolve this problem and I will do that. However if my tires were 25% down last year, to my opinion there is something wrong with the tires. I just cant see that with a new car I have to check the tires pressure every so often which I will find it very inconvenient especially during the winter months

My summer tires are now in the cabana and I inflate them to 40Lbs. Next spring after I get them inside the garage I will check the air pressure and if it is lower I will take them to the dealer to see what they say. In the mean time, I will monitor the air pressure on my winter tires to see if I have the same problem with them. I hope I will find no problem with them because I drove with these tires from Feb-2013 to Apr-2013, plus Dec-2013 to Apr-2014 and without checking the air pressure during that time I never had a problem.

But no one mentioned how the TPMS warning works. How that system works?

Perhaps I'm loosing air thru that system?

[akirby]

You say you never had a problem, but you don't really know if you did or did not have a low tire because you never checked it. The TPMS only warns you if they're 25% low. It won't tell you if they're 20% low. And different tires and even different wheels can have different results.

 

These are my results, and I check air pressure at least twice per year. I have a 2012 Focus, 2013 Fusion and 2014 Escape. The TPMS light came on in the Escape so I checked and filled every tire on all 3 vehicles. Every single tire, without fail, was between 6 and 10 lbs too low.

 

If your tires are at 36 psi on a 70 degree day then on a 30 degree day they'll be at 28 psi and that's without any leaks - just normal pressure change due to temperature. That's why you need to check them at least twice per year - summer and winter after the temps stabilize somewhat.

[akirby]

You're not losing air from the TPMS. That system sends the pressure from inside the tire electronically.

 

What we're telling you is that it's entirely possible that the pressure loss was normal even though it may not be what you've experienced before. It could also be a bad tire, wheel or valve stem. Only way to know is to monitor it weekly or monthly at the most.

[oskar27]

Thank you akirby, glad is not the TPMS. I will monitor the pressure as your saying

[oskar27]

Here is an update to this problem. Last month I removed the summer tires from my cabana and got them in my garage to switch my winter tires. Before I stored them in the cabana last December, all 4 summer tires were inflated to 40PSI and when I checked the pressure in my garage both rear tires were flat completely but the front were at 40PSI.

 

So now I know I have a major problem with the 2 rear summer tires (these are the original 18” summer tires with about 20k kilometers on them). I found no visual defects so I inflate them again and after one month and perhaps 500 kilometers the tires are ok (visibly)

 

I don’t want to check the pressure with my tire pressure gauge because I’m thinking perhaps the little valve inside the valve stem is defective and now it may sit properly so there is no air loss. If I disturb it with my pressure gauge it may start leaking air again.

 

I got a tool to remove the valve from the valve stem but I would like to know if this valve is connected to the TPMS.

 

Anyone has an answer?

[akirby]

You should be able to replace the valve stem without affecting the tpms, but it could also be the bead not sealing against the wheel.

[oskar27]

I understand that akirby, if no success next step is to replace the stem

[macbwt]

The TPMS is banded around the inside of the rim and positioned in the same location as the valve stem but are about two to three inches from each other. The valve stem and TPMS do not even come in contact with each other. Your probable air loss is one of several or combination of several problems. 1) Valve stem (replace each time you mount/remount tires) 2) bead of tire and rim is not sealing (clean the rim and wash the bead of the tire before mounting 3) rim may actually have a small hairline fracture (happens but not very often especially to two tires) Your most probable issue is the rim being dirty and not seating. There are products that can be applied to the rim to help seal the bead better so try that. Do not put slime in your tire unless you really want to buy and new TPMS sensor!!!!

[oskar27]

As mentioned, these are the original tires and with 24000 kilometers on them I doubt it the problem is with the valve stem or beat of the tire. Its amazing that you got 277k klicks in your 2008 Edge!

[macbwt]

I would be willing to bet your rim/bead seating is not good. I had this problem with a set of tires and it haunted me and the tire installer for a while until they clean the living h**l out of the bead and rim then applied a sealant to the rims. After that no problems. Thanks, but I did not get to this point on the Orange Crush without performing maintenance. How far no one knows? Maybe about September the pinned topic will state what to expect at 300,000 miles?

As mentioned, these are the original tires and with 24000 kilometers on them I doubt it the problem is with the valve stem or beat of the tire. Its amazing that you got 277k klicks in your 2008 Edge!