02 BMW 316 Possible Head Gasket Damage

spillcoe

Car was leaking coolant/water from the small tank by the radiator so I replaced this but now the water is overheating and the water pressure seems really high. I think this may be due to the head gasket being gone but I would appreciate any advice to either confirm this and give an estimate as to how much it would cost to get done.

Esel

Thermostat gone?

spillcoe

Any way of knowing for sure?

Anan1

Start the car from cold with the cap off the expansion (coolant) bottle. See whether there are any bubbles in the bottle. If not, give the car a little rev, see whether any bubbles appear then. Be careful to keep your face well away from the opening while doing this.

spillcoe

I did this earlier alright. There were no bubbles and I left the engine running and revving for a while until it heated up to normal temp with no problems. It was only when I took it for a test spin and came back to check it again that the water started boiling again. Temp gauge still showed normal though.

Captain Slow IRL

There's a procedure for topping up the coolant on these after a coolant loss - chances are you've only filled the overflow bottle. (got caught out myself as well!)

There's a little plastic bleed screw to the right of the overflow bottle cap - unscrew this. (item no.2 in this image) Then turn the ignition on (engine not running) and set the heater controls to the hottest setting and the fan running on it's lowest. Top up with water through the little bleed screw you loosened - it'll take a while, but make sure it is overflowing before you put the screw back in.

Hope this is all that's wrong!

Anan1

I'm no mechanic, but i'm thinking maybe the water pump. AFAIK, most thermostats are designed to fail open rather than shut. Are you in Dublin? If so, i'd bring it to AC Car Sales, they're a highly-regarded independent BMW specialist. I've only used them once myself, but I found them friendly, knowledgable and not too expensive.

Andrewf20

Why do you say the water pressure is high? It will expand in the expansion tank if thats what you are looking at. This is normal behaviour.

If the head gasket was gone, you are likely to get mayonaise coloured gunk in the oil that will show up on the oil filler cap. Also, if the head gasket was gone, the water level would drop.

How do you know it was boiling? I assume you removed the expansion tank cap to check. As far as Im aware, the boiling point of the water increases in the engine to say 120C under pressure, but as soon as you remove the expansion tank cap, the pressure drops and the water will boil. You may not have a problem after all.

DublinDilbert

Is your internal heater still working?

Ferris

Is the fan running? AFAIK the engine fan is run off a viscous coupling that can fail.

No hot air out of the interior heater fan would signify a problem with the cooling circuit, i.e. no water in the system, water pump failure or a fully open thermostat.

spillcoe

Internal heater is working, I did bleed it using the small screw alright but that didn't do any good. I was talking to a mechanic today though and he said it can take a while to bleed it properly so this could be the problem.

Andrewf20

Spillcoe, I get the feeling you are worrying over nothing, unless you can explain how you determined that the water pressure is higher than normal.

a) The system is designed to be under pressure.
b) The water will boil when the expansion cap is removed.

I dont see a problem!

Ferris

Damn Boyle's Law!

spillcoe

I'm pretty sure there is something wrong, there was a load of steam coming out of it before I opened the cap and that was just after a 5 minute spin.

spillcoe

Turns out it was just the cap on the expansion tank was faulty, I replaced it for 16 Euro and the car is running fine now. Only thing is there is I checked the oil and there seems to be a few spots of some milky/green liquid in with the oil, does anyone know what this is or am I just being paranoid?

Esel

Based on your previous concerns, I'd go with paranoid.