MBGLC300@

I had a warning light on all 4 tires yesterday. Went to Mercedes dealer and he put 31 psi on all tires. I drove off and it was fine. Drove less than 2 miles, parked. When I got in car again it said 28/29 psi warning on all 4 tires again! I have the run flat tires. I will take it to Mercedes again but has anyone had that happen without any crazy change in temp? I have a 2019 GLC 300

ygmn

could be leak in tire or cracked wheel.

MBGLC300@

On all 4 at the same time?

Tirgoman

First look on the sticker on the inside of the gas filler door and see what the pressure should be and that is when COLD. Then after you get the tires inflated to the proper pressure go into the menu for the dash and find Tire Pressure and press reset to establish that new pressure as what you want. Then I think it will warn you when it drops more than 5 PSI, you can read the manual for a more exact answer. The chances of all 4 tires having a slow leak is almost unbelievable but who knows. Taking the tire and wheel off and putting it in a water tank to see if there's a small leak will check that. I've had small leaks previously where a nail got in the tire and didn't leak just sitting there but as the tire rotated it pushed the nail and air leaked out on each rotation, but again, all 4 tires?

decorily

I think the advice on resetting given above is a good place to start.

Dealer may have inflated tyres but not reset.

Teckno

Agree with earlier advice re resetting tire temps from dash.
Dealer would have inflated to 31psi when tires were hot, so when they cool, alert would activate. He should have allowed for hot tire and put 3-4psi over recommended setting to allow cooling.
If Costco in your area and a member have them bleed tires of all ‘air’ and refill with nitrogen - tires run cooler, less leaking as molecules are bigger. Used in racing, only occasional in normal street use.
I would recommend filling tires to 36-38psi when cold, reset dash alerts. You will get better handling, better mpg and improved braking performance - safer. Downside, slightly harder ride !
Good luck.

fabbrisd1

I agree with the direction of this thread - #1 31PSI is too "low" - I prefer cold around 36PSI - and good suggestion to remember how to reset TPM yourself when needed.

Keep the beat !

MBGLC300@

Thank you! Can I put nitrogen on run flat tires?

Teckno

Yes , we have in Goodyear All Season runflats as well as Pirelli Scorpion Verde runflats, when originally fitted.
Nitrogen is basically oxygen, but bigger molecules, not dangerous.
Hydrogen however is a very different issue and should NEVER be used.
Nitrogen is very useful and safe.
Air is made up of about 78% nitrogen and about 20.95% oxygen, < 1% argon, and traces of other gasses such as carbon dioxide, and water vapor, among others.
the chemical element of atomic number 7, a colourless, odourless unreactive gas that forms about 78 per cent of the earth's atmosphere.

ot1

Nitrogen is not basically oxygen, one is inert and one is reactive. You will suffocate quickly in a high nitrogen environment, such as found in chemical plants and oil refineries. However its acceptable to breath pure oxygen! And i‘m pretty sure you wont find any tire shop trying to inflate your tires with oxygen or hydrogen or helium or argon or acetylene (Lol) unless they dont know their tank colors.

stath

I also got the sudden warning on 3 tires at 32PSI. (2018 GLC300). I put some air at the gas station and it went away.
BUT the weird thing is, I got new tires 6 months ago at the dealer. OEM runflats. I only drove 700M since. I park inside subterranean garage. No wide temperature changes.
WHY did the air leak so quickly??
So far I get a low air warning every 6 months... Really frequent with the GLC. Maybe all 4 wheels were deformed from the get-go?

LJE

I just had the same experience - I have had no issues - Scorpion Run Flat came with car, drove about 2 miles, parked, went home same distance and before I got back both the rear tire sensors reduced to 29 psi! Then the front did the same to 30 psi? How do all 4 at the same time lose air? I took it in and air was low - reset and filled accordingly… anyone else have this issue?

Teckno

You need to reset your low limits for tire when they are cold. Even though you have topped up tires, they were hot and were above low cold limit.
When you have driven to air place or dealer your tire pressures will have increased by around 3-4 psi. I recommend you set your cold pressure to 36 psi cold, so have them filled to say 39 psi to allow for cooling.
Higher pressure is safer, better handling, better braking with reduced stopping distance and better fuel economy, etc
Once home reset your lower and higher limits to fix this when tires are cold, before you go driving.
If you are still loosing air, check the air valve in tire stem is screwed in tight. Ensure dust cap is on stem too.
Good luck.

tylor1231

This guide help me understand reason of tire flating. Hope it will assist you too. Read Here

no_mulligan

If you want to rule out a leak, use windex and spray the tire, wheel, including valve stem. Any leak will start bubble. Better than soapy water.