Tyre valve problem - help needed

[rs666]

Having problems with one tyre/valve.

RR'd the car the day I bought it and afterwards the NS front had lost 10psi. So I pumped it back up and no problems, stayed at 40 psi for another 5 weeks.

I then RR'd it over Xmas and it lost 10psi on the RR. I reinflated and went home. Car spent 2 days on drive and the tyre deflated to about 15psi, so I reinflated and it has stayed at 40psi for another 5 weeks.

Last night get in the car and it was back at 30psi, reinflated to 40psi, but this morning its back down to 30psi.

My question is...is this likely to be a tyre or a valve problem? Given the tyre has stayed properly inflated for a number of weeks I don't think its a slow puncture.

If its valve, can it be replaced and if so, what about the pressure monitor? Isn't the sender built into the valve?

[peterb]

A few thoughts about intermittent pressure loss - could it be a damaged rim or tyre bead (or even puncture - embedded nail?), which only leaks when a certain section of the tyre is in contact with the ground?

As far as I'm aware, the pressure monitor/sender is located in a large block mounted behind the valve stem inside the rim - I don't think the valve stem can be replaced without disturbing the sensor inside the tyre/rim. However, the actual valve insert (which screws into the valve stem) can be replaced very easily - it's part no. 908 733 01. Many old-fashioned, pencil-type, pressure gauges have a small tool in the end for unscrewing the valve insert, or special valve tools can be obtained.

I would guess that the valve insert is no different to any other schroeder valve insert - you must be able to buy these at Halfords.

[rs666]

So how do I go about this without going to a tyre fitter who will inevitably give it the big intake of breath and get a two tyre sale out of me?

[peterb]

What, changing the valve insert? Go along to Halfords and buy a pack of the inserts (and a valve tool, if you don't have one). Deflate tyre, unscrew old valve, screw in new valve, re-inflate.

Checking for leak which is sensitive to tyre angle? First of all, I would take the wheel off the car and check very carefully all the way round for any signs of foreign object. Otherwise, just monitor the position of the wheel everytime you park and see whether there is any correlation between the wheel position and the loss of pressure. If there is any correlation, then it is almost certain that the leak is due to some problem in the wheel/tyre somewhere close to the area that is in contact with the ground.

[confusionhunter]

ok.... what to do is get some washing up liquid, place a little buit in the valve and you should see any bubbles come out if its leaking.... As its intermittent, When the Tyre leaks over night mark the tyre with chalk where it meets the ground (or just remember where it is in relation to the Tyre valve) and place some Fairly Liquid around the rim, again watch for a few mins for any kind of bubbling through air leaks.
Failing that take the wheel off and inspect the tyre tread looking for stone and nails... if you find anything bear in miond if you remove it it might make the leak worse! put FL round the whole rim and watch for leaks, and then try the back of the rim, especially around the area of the chalk mark.

If the leak is from the valve, try tightening it (any tyre fitter will have a key).
If its from the rim, the tyre should be removed and the have rim cleaned up removing crap , corrosion and dirt) apply "soap"( what they call the white stuff they use as joining compound) and refit tyre.

If the tyre has a slow puncture you can get that fixed reletively cheaply.

failing that, try some Tyre weld!!!!

[SimonS4MTM]

Take a look here for info on the pressure sensor and how it fits

www.f1systems.com
www.beru.com

[rs666]

Just got back from local ATS.

They inspected the tyre, no problems. Bathed it in concentrate (FL )....nothing!

Has held its pressure since this morning, so they advised the same. Put it back on and monitor tyre position.

Whilst there they quoted me £739 for four PS2's!!!

So will be borrowing some of my daughters chalk this weekend

[confusionhunter]

Maybe they got the 9 and 7 mixed up???

[rs666]

nope, they are doing a 25% off if you buy four Mich's