So on the original cooling tank container the top center area started to bulge as if it was going to explode. Never did but still had that look. I replaced it with a SS version and the same thing happened. Does anyone know why it keeps doing this? It the engine or coolant getting super hot? Is there something going on that I need to check? Any help/guidance is appreciated.
Is your car running a little on the hot side? I am going to be bold here and say that gases in the cooling system MAY indicate that air is getting in from the outside or exhaust gases coming from the inside (gasket leak). The first may be easy to find and diagnose and fix the later not so much.
In theory the expansion tank cap will release pressure at ~.9 bar. So unless your cap is defective, the system shouldn't explode! And chances are a hose will let go before a steel tank.
I'll try to get a picture up by tomorrow. The car was running a little hot before but that has not been an issue since installing some new parts (expansion tank w/new cap, hoses, plugs, wires, cap, rotor, etc). Also, is it normal for coolant to leak out of the expansion tank drain hose after a couple of hours of driving?
It has been "said" here many times and I will repeat the wisdom "bleed, bleed, bleed". After installing new parts there may just be air in the system? It's the bubbling sound that is the tip off that gases or air is in the system.
I used to get this frequently, but only because: a) I'd over-filled it; or b) There was air in the system. (b) can be a real PITA to correct (in my experience). The procedures for bleeding are easy enough to follow, but there's a fundamental design flaw in some of the expansion tanks (again, IMHO) that allows air to be drawn into the system once the car is parked and everything cools down.
Two things IMO: 1. the opening pressure of your radiator cap (The Stant hand pump for pressurizing the cooling system, and looking for leaks, can also be used to test the opening/relief behavior of the radiator cap). 2. If that's OK (but you still get the bulging), you might consider checking the fittings on the engine for both the small hose and the larger hose of the expansion tank -- these fittings can corrode fairly badly and their ID may be blocked/restricted. (Although, if the radiator cap is working properly, I can't say why this would make a difference ).
I think you said the tank was new so this shouldn't apply ... but ... I worked on a car on which the overflow hose/nipple was plugged so the cap couldn't purge. The nipple on the tank that the overlow hose connected to was pretty small ... smaller than some other tanks I've seen on 308's FWIW so it seemed like it would plug easy.
I installed a overflow tank off of the expansion tank and have not had to bleed it since. Every time I have checked the expansion tank it has been full also.
+1 I had a buldging tank, and that little steel tube below the rad cap was blocked with rust (very small, easily clogged). stuck a coat hanger through it and reamed out the rust and voila it now blows off as it should.
