Overheating help needed please. 97 318ti

[jca]

Good question. You've gotten some good info. from Jess and Zoner. Air bubbles visible in the overflow tank while the engine is running is one symptom. Take out the plugs and shine a good flashlight down each cylinder. If one or more piston heads are shiny and clean the gasket is probably compromised. Reason: coolant leaking into the combustion chamber cleans the piston head in a short time. A related symptom is a rough idle just after starting the engine which smooths out quickly. Reason: residual coolant in the combustion chamber causes the plug to misfire until it evaporates out of the running engine. My engine had all three of those symptoms plus overheating after about 15 minutes of driving. I did not have white smoke coming out of the tail pipe or visibly contaminated oil.

[cooljess76]

In my opinion, the best/ONLY way to diagnose a head gasket if the obvious signs(coolant/oil mix, loss of coolant, white smoke out of the exhaust, chocolate milk under valve cover and dipstick etc) aren't present is to perform a leakdown test. It's more involved than a compression test, but it'll tell you with certainty if your gasket is compromised. Don't waste your time with all of the other BS tests people will try to sell you on. The longer you wait and continue to drive the car, the more likely you are to blow the head gasket and possibly warp or crack the head. Chances are if you've already overheated it, you've significantly reduced the life of the gasket. Every second that the engine temp goes above 12 o'clock on the gauge, takes 10's of thousands of miles off of the life of your gasket.

[radicalr6]

it is most probably head gasket or the head itself. I just got back to the garage and tried to do a flush. Car turned on, heater blasting, adding water. But there is always a large ass bubble coming out from the bleeder on top. Iv flushed it for 10 minutes and always there. Drove it after, flushed again and still there

[jca]

All or some of these symptoms: white smoke out the tailpipe (water vapor); milkey subance on the underside of the oil filler cap (water/oil emulsion), overheating, of course, inability to purge all the air from the coolant system...bubbles just keep coming; engine misfires when cold then smooths out quickly (moisture leaked into a cylinder, then burned out); one or most piston heads shiny and clean ( the coolant cleans the carbon off the piston head). Coolant disappearing in the absence of any visible leak. Jess says that the definitive test for a blown headgasket is a leak down test. Mine had: shiny piston head, misfiring, overheating, disappearing coolant, and unending bubbles, and coolant that smelled of gasoline. Good luck. John

[radicalr6]

Originally Posted by jca

All or some of these symptoms: white smoke out the tailpipe (water vapor); milkey subance on the underside of the oil filler cap (water/oil emulsion), overheating, of course, inability to purge all the air from the coolant system...bubbles just keep coming; engine misfires when cold then smooths out quickly (moisture leaked into a cylinder, then burned out); one or most piston heads shiny and clean ( the coolant cleans the carbon off the piston head). Coolant disappearing in the absence of any visible leak. Jess says that the definitive test for a blown headgasket is a leak down test. Mine had: shiny piston head, misfiring, overheating, disappearing coolant, and unending bubbles, and coolant that smelled of gasoline. Good luck. John

So did yours prove to be a head gasket?? or was it something else?

P.S Could this be due to a bad hose of letting air get in the system?

[X E Ryder]

Can I ask what the status of your Thermostat and Waterpump is? The first thing I did was swap both as I understand high mileage BMW's need this, and what was pulled was pretty rough.

A sticking thermostat can be tricky to diagnose, the waterpump a little easier because engine speed correlates to water temp when you have a worn pump impeller.

Also, not sure if this applies, but when I bleed a cooling system, I park nose up, diagonally right, and run the heater on high to insure the heater core does not trap air.

Just a couple thoughts.

[radicalr6]

Originally Posted by X E Ryder

Can I ask what the status of your Thermostat and Waterpump is? The first thing I did was swap both as I understand high mileage BMW's need this, and what was pulled was pretty rough.

A sticking thermostat can be tricky to diagnose, the waterpump a little easier because engine speed correlates to water temp when you have a worn pump impeller.

Also, not sure if this applies, but when I bleed a cooling system, I park nose up, diagonally right, and run the heater on high to insure the heater core does not trap air.

Just a couple thoughts.

I changed the thermostat. Haven't changed the waterpump

[jca]

Originally Posted by radicalr6

So did yours prove to be a head gasket?? or was it something else?

P.S Could this be due to a bad hose of letting air get in the system?

Yep, it was a bad headgasket...

[jims318i]

I'm new to this site and I can't post. I got the same problem that started after changing-Radiator-Hoses-water pump-and thermostat. I can drive the car several hundred miles and then it will shoot coolant from the tank. There is no rhyme or reason that I can come up with. Suggestions? Thx

[Lbcnu24]

I actually have a coolant issue, but its different. My fan does not kick on at all! I changed the fan switch, nothing, no help there... But, if I turn the A/C on, the fan runs fine. So I have to run that A/C in order for it to run the fan to keep it from over heating. I wonder what I have to do next, since it is not the fan switch... anybody?

[Honolulu]

Lbcnu24... if you have a different problem (and you do), don't hijack someone else's thread, start your own.

IIRC the fan can be actuated two ways. One is when the AC is turned on, the other is from the coolant temp switch.

Activating the AC turns your fan on, so that part is okay so drive with the AC on, my wife never goes anywhere without.

The fan is controlled not only by the CTS, but there is a fuse, and a relay. That's where I'd go next in your situation. Both can be tested, and I wouldn't replace either without knowing it was bad.

Also... the fan has high and low speeds, doesn't it? If so there is a resistor that controls the speed. Get familiar with the electrical diagram for the fan, it's online though I don't have the link just handy.