[esa1969]

So after running the car for awhile with the heat on the low coolant light starts coming on and off. Only after running for 30 minutes or so( no over heating and gauge in the middle) I turn the car off and a few minutes later it moves the top radiator hose back from the settled position causing it to leak.
Any advise would be appreciated.

 

[swordsman11868]

Sounds like the hose is not fully seated in the radiator.

Pull up the clip and seat the hose. Then push the clip back down so it engages the locking rings.


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[esa1969]

Did that twice and some how pressure is pushing it back causing a leak.

 

[esa1969]

What would cause this back pressure and the low coolant light coming on and off while driving and no coolant lost.

 

[Newbimer]

You do not need to lift the locking clip to install the hose. Actually, you should leave it down when installing so you hear it click when its full inserted. Back pressure can be caused by air in the system that expands when heated, combustion leaks into the cooling system, could also be a bad rad cap not releasing excess pressure in the system. Let it cool completely, check the cold level, add if needed then make sure you bleed the system properly.

 

[Sapote]

I turn the car off and a few minutes later it moves the top radiator hose back from the settled position causing it to leak.

It moves the hose; what moves the hose?

Lube the radiator port and the hose connector O-ring with brake grease (synthetic grease) and with the clip fully inserted, push the hose on the radiator port until the clip is clicked over the port barb.

You still have air in the system which might cause the coolant light on/off.

 

[esa1969]

The radiator cap is after market. How would I tell if it's releasing the pressure correctly?
I replaced the overflow box and thermostat 2 months ago and this is the first of my issues.

 

[77'911]

Had this issue when a shop installed after market coolant parts(tank, cap , upper hose t-stat, etc) on our car. Installed factory BMW parts, no leaks after 12+ months. Our car would leak coolant if you just touch the upper hose, the connection fit was that poor. Welds on the reserve tank were bad when new.
regards

 

[jmo69]

The system should be building enough pressure to vent through a stock 2.0 bar cap. Never vented with my 1.4 bar cap. Sounds like you need a new hose, you can get a Rein at Autozone, around here it's $48 or Amazon for $31 https://www.amazon.com/CRP-Automotive-CHR0001P-Rein-Radiator/dp/B00K2PP4MW/ref=sr_1_1?keywords=upper+radiator+hose+2003+bmw+325xi&qid=1581661969&replacementKeywords=upper+radiator+hose&sr=8-1&vehicle=2003-31-176------------&vehicleName=2003+BMW+325xi A friend just replaced his with that one. Has the system been bled properly or been over filled. Air in the system will compress but the coolant wont.

 

[MrMCar]

The O ring is worn (shrunk) from age. If OE hose and young there is no movement.
The movement is caused by expansion/contraction.

 

[markusmarkus]

The installation of aftermarket cooling system parts is strictly verboten!