On my 94 Coupe, very odd... my right rear passenger side tire is going flat. Sometimes. I parked it at night, and the next morning, it was completely flat. I filled it up with air, and it was fine for a couple days. No loss of pressure. Then all of a sudden, overnight, it was completely flat again. The shop checked the tire, couldn't find any leaks (sprayed with water, looking for bubbles...).

Could it be a 'positional' thing, that depending where the tire is left overnight touching the ground, it is opening a seam somewhere and losing air?

There is plenty of tread left, so I don't really want to buy a new tire. I imagine putting in a can of stop-leak is a bad idea, so what else can I do?

 

I think you should post it on the forum for some useless responses


You have two options
1 Buy new tire
2 Keep filling it up with air

 

Check the schraeder valve for leakage. Inspect the tire carefully for any foreign objects embedded in the tread. It could also be leaking at the bead, but possibly only when the car is parked with the tire/wheel in a certain position (sidewall flexure contributing to the intermittent leak). Check the valve stem where it seats in the wheel.

Fill a spray bottle with soapy water, and spray the tire down daily, looking for bubbles. Sooner or later, you'll probably be able to spot the leak if you're persistent enough.

Be well,

SJW

 

Does my car have one of those low-tire pressure warning systems? I'm wondering if that thing could have somehow 'sprung' a leak? (No idea how those work, anyhow).

 

With a leak that slow pouring water over it may not show bubbles. If you have a kiddie wading pool pull the tire and wheel off and fill it up to about 50 psi. Put it into the pool and submerge it and then look for air bubbles. Just don't get to wild on the air pressure.

 

Check your RPO codes to see if you have that option, but it doesn't sound like you do. Sensors are mounted inside the rim and transmit data to reciever in the cockpit. In any event they could never cause a leak. I am with SJW, schrader valves can act weird (ancient technology) and since they cost about .10 I would replace it. 94Z1 said you had 2 choices, actually there are many:

new valve
new valve stem and valve
new tire
new wheel
new tire shop
all of the above, or
none of the above, and
keep airing the tire
sell car and let next guy worry about it
park it and forget it.

I am thinking #1 or #2 is most likely.

 

You don't state how old is the tire; that could be an issue if it's actually seeping air through the sidewall or tread area.

The bead leak is very possible, too, as well as the valve and stem. And it may not show so well as said by George.

Question: when the tire shop had it off and looking, did they deflate it, scrub down around the rim contact area with the tire and then refill with air?

Question: can you recall hitting any potholes, bumps, curbs, railroad tracks recently that might've caused this? It doesn't always take a bone-jarring hit; just the right way at the right speed can cause a slight, internal damage which could then lead to a leak. So, think back.

 

I had a similar problem about a year ago. I had four new tires and one of them had a very slow intermittent leak. I went back to the tire shop several times and they could not find the leak. They tried to blame it on the rim. Finally I was able to persuade them to replace the tire for a new one. Problem solved. Hope that helps.

 

The tire is questionable, it came with the car when I bought it a month or so ago, so no idea how old it is. I'd wager there is 30-40% tread left on the tire.

And yes, I can recall totally smashing over a black speed bump in a dark car garage... full speed. About three weeks ago. I was really pissed... who the frick installs black speed bumps in a dark enclosed parking garage? Jerks.

I like the idea of taking the tire off and putting it in a kiddie pool, I might try that this weekend... otherwise, are you guys particular on tire shops, or just go anywhere? I wonder if BJ's WholeSale club carries my tire size...

 

Do you park it outside? Maybe it's the neighborhood kids messing with you?

 

Bet that tire has a nail in it or the valve stem is bad. You can check it yourself using a thick solution of water and DW detergent. You need to take it off the car. If not, take it too a full servce neighborhood service station that sells tires and have them check it.

 

Just to add more input: I had a car that would have one tire go flat after a very cold night and at no other time. It was not my Vette. Another weird flat (very slow) was attributed to a porous alloy rim. After tire removal, rim cleaning and interior repainting (twice), the problem went away. Was it really caused by a poor quality casting? Who knows, but that's what my tire experts thought

 

Have your wheels been chrome plated? I've seen slow leaks caused by air seeping between the chrome plating and the aluminum base metal in the tire bead area.

 

I realize this is a resurrection of an old thread but I've had a few issues with slow leaks in the past. Obviously a nail, porous wheel, tire bead not sealing properly and cracked valve stem. Best thing I've ever found was a kids wading pool. Fill it up and submerge the tire in it, use a concrete block on the tire if need be. If after a while you don't see it on one side, flip the tire over. Porous rims are the hardest to find depending on how porous they are, some may only give a bubble every few minutes.

 

I had new 35 inch BFG mud tires that I had changed out for street tires on a four wheel drive. The tire shop damaged the beads so badly on every tire they had large flaps of cut, loose rubber and of course they refused to replace them because they said they were fine. The manager came out and said he guaranteed they're fine so I said I'm not going to take a risk of coming back in a few months and have them deny everything so I wanted new tires. They kept arguing and refused.

I had them mount them right then to prove it and they held air and gave me a written guarantee. I had them changed out once or twice after that and they never leaked even when I aired them down for off-roading and through summer, winter, mud, snow, and dirt.

I know tire beads can leak and I know car tires don't have as large of a bead as a 35in off-road tire, but this did tell me something. A car tire, especially a sports car tire, should always have high enough air pressure in it to seal the bead. If the rubber is clean, and the rim is clean, undamaged, not oxidized, smooth and undamaged, not bent, and the rim and tire width match, you should almost never have a leak that is noticeable in less than a few weeks.

Tire sealant drys and gets sticky and I'm certain that it would help seal a bead but that extra goop floating around the tire is not ideal. Even though sealed I think it could dry and/or cause a balance issue, but if it stays liquid it should flow evenly around the inside of the tire.

 

Take it to Discount Tire. They will check it, and if repairable, will fix it FREE!

 

After almost 12 years, I'd bet he has new tires

 

 

Probably a new car or two after 12 years.

 

A couple of possibilities:
Do you have chrome wheels?
My Son's car was doing that slow leak down and we found out that the chrome under the bead had deteriorated. It had tiny cracks in the chrome letting the air out slowly over a couple of days depending on which part of the tire was against the ground.
Bad air valve stem.
Had a tire intermittently going down like yours. Sprayed water/soap...no bubbles!?! Took it off the car and scrubbed it clean and tested again....no bubbles. Put it back on and it was low a couple of days later!
Aired it up again and while checking the pressure with a gauge, I moved the valve stem a little to the side and...pissst, escaping air! Wiggled it again and each time got a hiss of air. When not pushed sideways it sealed and didn't leak at all! I guess the bouncing on the road was enough to wiggle the stem and leak, but NOT leak when sitting still. New valve stem and all got well.