What may cause the rear suspension drop intermittently?

[celica]

I changed the rear air bag suspension two years ago as the rear was always sagging overnight

Now it’s sometimes on rear left

Can it be air bag suspension again, other?

I don’t understand as it’s sometimes. It rises back up after a short drive

[marti]

You must have leak.....

[celica]

I do have a leak

I’ve heard a hissing noise when it drops which is sometimes when parked up

What could it be?

Assume not fault air bags as if it’s worn like the old ones it would always leak

I’m confused to understand what it could be?

[X5Sport]

Could be bags, hoses, valve block, connections in pipes etc.

[celica]

[quote="X5Sport"]
Could be bags, hoses, valve block, connections in pipes etc.
[/quote]

Thanks

But what would cause intermittent leakage?

My old bags I saw perished and so leakage was always happening over time

But this is only sometimes?

Getting oil change next week so will get garage to diagnose

[X5Sport]

It could be temperature or load related.  Something causing a hose to move slightly and give rise to a leak, or a seal/valve being affected by higher temperatures.  A bag may have gone bad again but needs to be at the right angle for it to leak.

Even the difference between a full and empty fuel tank might be enough.

[celica]

Just been for an oil service

The garage had a look and couldn’t see anything obvious

It’s annoying as couldn’t replicate the drop

Yet even on a flat at a car park the other day it dropped

Could it be electrical? Could it be the heat we’ve had?
I heard an apparent hissing noise of air leakage before but strange how it’s intermittent

Not sure whether to throw money and put on a new air bag

[celica]

I think for the price I’m going to purchase Aerosus airbag and a solenoid valve blockas it’s free returns and take it to my trusted mechanic to inspect and at least have options to change parts if required