Intermittent loss of tire pressure in one tire

This has me perplexed.

One of my relatively low milage (3000 mi) tires loses air pressure
intermittently - every 5 months or so I will go out and the tire will
be almost flat - over a short time period ( i.e. a day) it loses
pressure to the point it is flat. I'll pump it up and it will be fine
for another few months - and then suddenly it is flat again. I had the
garage rotate the tires last spring and they checked the tire - no
nails etc and replaced the valve stem. The only difference after
rotation is that the tire leaking is now on the back!

Nothing special about the car or the tires - standard Mercury Mystic
Sport

The car is in a garage, so it is not kids.

Suggestions?

wrote:
> This has me perplexed.
>
> One of my relatively low milage (3000 mi) tires loses air pressure
> intermittently - every 5 months or so I will go out and the tire will
> be almost flat - over a short time period ( i.e. a day) it loses
> pressure to the point it is flat. I'll pump it up and it will be fine
> for another few months - and then suddenly it is flat again. I had the
> garage rotate the tires last spring and they checked the tire - no
> nails etc and replaced the valve stem. The only difference after
> rotation is that the tire leaking is now on the back!
>
> Nothing special about the car or the tires - standard Mercury Mystic
> Sport
>
> The car is in a garage, so it is not kids.
>
> Suggestions?
>

When mine do that, it is a rim leak. It goes down 'very' slow to a
certain point, then the tire against the rime pressure is lower and you
park wrong and it drops overnight.

The garage can almost never find these because they blow the tire up
hard to test it so the leak gets sealed. If they put it in their water
tank with only 10 psi, they would have a better chance of nailing it.

I usually just tell them to dismount it and clean it 'if' they cannot
'find the leak'. The last place argued with me until I got the manager.
he was more than happy to take my money and clean the sucker. It was
-30 out and I have 30 psi in the tire. They test it at 40 psi in 75 F
temps...

Thankfully those Aluminum rims went to the rust pile with the rest of
that Jeep.

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

> wrote:
>
>One of my relatively low milage (3000 mi) tires loses air pressure
>intermittently - every 5 months or so I will go out and the tire will
>be almost flat - over a short time period ( i.e. a day) it loses
>pressure to the point it is flat. I'll pump it up and it will be fine
>for another few months - and then suddenly it is flat again. I had the
>garage rotate the tires last spring and they checked the tire - no
>nails etc and replaced the valve stem. The only difference after
>rotation is that the tire leaking is now on the back!
>
>Nothing special about the car or the tires - standard Mercury Mystic
>Sport
>
>The car is in a garage, so it is not kids.
>
>Suggestions?

Take it to a better tire shop and have them submerge it, then reduce the
pressure. If they don't find anything, have them clean the lip of the
rim and see if that fixes it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Mike Romain > wrote in article
om>...
> wrote:
> > This has me perplexed.
> >
> > One of my relatively low milage (3000 mi) tires loses air pressure
> > intermittently - every 5 months or so I will go out and the tire will
> > be almost flat - over a short time period ( i.e. a day) it loses
> > pressure to the point it is flat. I'll pump it up and it will be fine
> > for another few months - and then suddenly it is flat again. I had the
> > garage rotate the tires last spring and they checked the tire - no
> > nails etc and replaced the valve stem. The only difference after
> > rotation is that the tire leaking is now on the back!
> >
> > Nothing special about the car or the tires - standard Mercury Mystic
> > Sport
> >
> > The car is in a garage, so it is not kids.
> >
> > Suggestions?
> >
>
> When mine do that, it is a rim leak. It goes down 'very' slow to a
> certain point, then the tire against the rime pressure is lower and you
> park wrong and it drops overnight.
>
> The garage can almost never find these because they blow the tire up
> hard to test it so the leak gets sealed. If they put it in their water
> tank with only 10 psi, they would have a better chance of nailing it.
>
> I usually just tell them to dismount it and clean it 'if' they cannot
> 'find the leak'. The last place argued with me until I got the manager.
> he was more than happy to take my money and clean the sucker. It was
> -30 out and I have 30 psi in the tire. They test it at 40 psi in 75 F
> temps...
>
> Thankfully those Aluminum rims went to the rust pile with the rest of
> that Jeep.
>


Another thing that I have seen is a nail, screw, or other foreign object in
the tire tread.

Most of the time, the leak is so slight that it is virtually, unnoticeable.

Occasionally, you park with the foreign object against the roadway, and the
hole opens a bit and allows the tire to deflate more rapidly.

wrote:

> This has me perplexed.
>
> One of my relatively low milage (3000 mi) tires loses air pressure
> intermittently - every 5 months or so I will go out and the tire will
> be almost flat - over a short time period ( i.e. a day) it loses
> pressure to the point it is flat. I'll pump it up and it will be fine
> for another few months - and then suddenly it is flat again. I had the
> garage rotate the tires last spring and they checked the tire - no
> nails etc and replaced the valve stem. The only difference after
> rotation is that the tire leaking is now on the back!
>
> Nothing special about the car or the tires - standard Mercury Mystic
> Sport
>
> The car is in a garage, so it is not kids.
>
> Suggestions?
>

I'd suspect that your rim has a rough spot on the bead so that when the
tire is sitting with the weight resting on just the right place, it
develops a leak.

On Sep 11, 12:16 pm, wrote:
> This has me perplexed.
>
> One of my relatively low milage (3000 mi) tires loses air pressure
> intermittently - every 5 months or so I will go out and the tire will
> be almost flat - over a short time period ( i.e. a day) it loses
> pressure to the point it is flat. I'll pump it up and it will be fine
> for another few months - and then suddenly it is flat again. I had the
> garage rotate the tires last spring and they checked the tire - no
> nails etc and replaced the valve stem. The only difference after
> rotation is that the tire leaking is now on the back!
>
> Nothing special about the car or the tires - standard Mercury Mystic
> Sport
>
> The car is in a garage, so it is not kids.
>
> Suggestions?

Have someone look over the tire very carefully for a small nail or
screw imbedded in the casing. It has probably worn down to where it
is all but invisible. They can hold air just fine, but park the wheel
at just the right angle and it breaks the seal and down goes the tire.

On Sep 11, 1:16 pm, Mike Romain > wrote:
> wrote:
> > This has me perplexed.
>
> > One of my relatively low milage (3000 mi) tires loses air pressure
> > intermittently - every 5 months or so I will go out and the tire will
> > be almost flat - over a short time period ( i.e. a day) it loses
> > pressure to the point it is flat. I'll pump it up and it will be fine
> > for another few months - and then suddenly it is flat again. I had the
> > garage rotate the tires last spring and they checked the tire - no
> > nails etc and replaced the valve stem. The only difference after
> > rotation is that the tire leaking is now on the back!
>
> > Nothing special about the car or the tires - standard Mercury Mystic
> > Sport
>
> > The car is in a garage, so it is not kids.
>
> > Suggestions?
>
> When mine do that, it is a rim leak. It goes down 'very' slow to a
> certain point, then the tire against the rime pressure is lower and you
> park wrong and it drops overnight.

what he said. My dad had the same issue on his Scout, turned out to
be some wood between the rim and the bead from hitting a tree. It
looked OK but tire needed to be dismounted and remounted, then all was
good. It would only go flat if it was parked with the bad spot down,
then the weight would cause it to slowly leak out overnight.

nate