Bubbles in matrix finally sorted!
 

Ever since I brought my car nearly 3 years ago I sometimes had a water fall noise coming from the heater matrix for the fist few seconds after starting the car from cold.

Even after many coolant changes and bleeding the system it wound eventually come back. I tried many different ways (back filling through the turbo coolant pipe ect)

When the engine was removed to be forged the builder commented that it has been a bugger to bleed, At the 1000 mile run in service they had another crack at it but still water noise would some times re appear.

That was nearly 2 years ago now and since then I've become a custom to it.

So I was at Cotswold Subaru the other day collecting a new bov gasket when we got on the subject of car problems, I brought up the water noise problem and first thing he mentions "Oh your want a new set of rad caps"
I've checked them in the past but never seem to find a problem.

Anyway brought a set of oem caps and poped them on the following morning when the engine was cold, checked the coolant was toped up and went for a drive, Following morning no noise! That was Friday last week and since then still nothing!

Apparently they do weaken over time, This causes the coolant to begin to release tiny bubbles on the verge of boiling as its not being kept under enough pressure, This can end up causing little pockets of air that your hear in your heater matrix.

If left unchecked over time the cap could completely fail causing the coolant to total boil and overheat your engine.

The coolant system can deal with a bit of air as it will find its way to the header tank and be past through to the expansion bottle. But if your cap is weak it will be causing a constant problem of little bubbles to deal with.

For £35 a worth while investment if you've not changed them already. Attachment 31465

Top info mate :thumb:

Great info.