Overheating and air bubbles

[novice318tiowner]

I have a 1997 BMWti. Three weeks ago the plastic piece attached to the back of the head that's part of the cooling system broke and I ended up blowing my head gasket in the process. My father and I ended up replacing the piece and the gasket. Not even an hour later, my engine was getting hot. This time I thought it was because of my heater core. I took a hose connector and bypassed the heater core. It got hot AGAIN! The vent screw was broken, so I figured that it maybe because of that. So I got a new one. It's still getting hot on me and each time my coolant level is way low. Each time that the car starts getting hot, it's been while I've been idling for at least 5-10 minutes. As soon as I start moving, the temperature guage moves back to the half-way mark. I drained my radiator and filled it up with 50/50 coolant. I had my car on an incline with the nose facing up. I had my car idling while i was filling, but after 30 minutes air bubbles keep flowing out of the vent. While i was filling, the temp stayed at half-way though. I have been told that I may have blown my head gasket again. However, three weeks ago when my gasket blew, my car was shook violently afterwards and when I tried to fill up the reserve with coolant, no fluid came out of the vent at all, but I could see air bubbles flowing into the reserve. This time the car has a smooth idle and fluid is coming out of the vent, I just can't seem to get all of the air bubbles out. We had to file down the head by 12/1000 of an inch when we replaced the gasket, so I really don't want to have blown another gasket, which means buying a new head. Does anyone know what could be wrong, or do I have to suck it up and buy a new head and gasket?

[cooljess76]

http://www.318ti.org/forum/showthread.php?t=27983

Welcome to the site!

[novice318tiowner]

I did exactly what that the thread u directed me to said to do, except for getting all of the air bubbles out. How do I get all of the air bubbles out?

I parked on an incline. I messaged the radiator hoses that ran to and from the thermostat and tapped on top of the radiator and still air bubbles were coming out of the vent.

[cooljess76]

Was the engine running? Did you have the heater on full blast? Did you cap everything back off, drive the car around the block, let the engine completely cool and repeat the process? How many times? If the bubbles never stopped, why did you stop bleeding it initially? I mean technically, if you're seeing bubbles coming out of the bleed port, that's a good indication that there's air in the system. You should've kept filling it until you witnessed a steady stream of coolant coming out of the bleed port.

When you're filling it, bring the coolant level up all the way to where coolant is about to spill out of the threaded neck of the expansion tank. At that point, you should see coolant coming out of the bleed port with tiny bubbles in it. Cap everything back off, drive it around the block once or twice and park it on the same incline. Let the engine cool for a couple of hours. This will give all of those tiny bubbles a chance to combine into a few big bubbles. Start the car and repeat the process. It usually takes several tries to get all of the air out of the system.

You can also use an additive by RedLine called Water Wetter. It breaks the surface tension and helps the air bubbles combine. When you're bleeding the system, don't rev the engine or anything. Doing so will only cause coolant to shoot out of the bleed hole thus allowing more air to enter the loop.

That's all I got man, the bleed process can't be explained in any more detail than it already has been. You're either doing it wrong or something else is messed up. Perhaps your new headgasket is leaking. Did you take your cylinder head to a machine shop and have them check it for flatness and/or cracks? Simply looking at it and saying it "looks" straight isn't good enough. These things need to be level within 10 thousandths of an inch. That's why it's so important to properly torque them down in accordance with the manual.

Imagine what happens to a large piece of aluminum when you heat it up past it's tolerances, then dump water on it. The molecules are going to distort, it's going to warp or maybe even crack.

Another thing to consider is that the plastic "Y" fitting on the back of your head was old and fatigued. Chances are, the rest of the cooling system is too. There's another plastic fitting on the driver's side of the engine block that is also known to crack. It should be replaced too. Both of these plastic pieces are common fail points. There's been several threads in regards to them breaking and dumping coolant.

It's highly recommended to replace THE ENTIRE cooling system if you want to keep driving your car for years to come. The radiator, water pump, thermostat, hoses, plastic fittings etc can only be expected to last for so long before they become fatigued and brittle. Anytime you open the coolant loop, ie replace a part, it's very important to bleed the cooling system. For this reason, I recommend replacing everything in one shot so you're not constantly having to re-bleed the system and risk overheating. Every second that the engine goes above normal operating temperature(12 o'clock on the temp gauge), you're comprimising the integrity of the head gasket. It might not fail immediately, but rest assured it has suffered some level of fatigue.

And finally, I'm not pointing blame or ignorance. I don't know who owned your car or how it's been driven/maintained. I'm just explaining why things happen based on my own experiences and observations. Best wishes, hope you don't have to replace another head gasket, but if not done properly, you probably will.

[novice318tiowner]

I'll be the first to admit that I am a novice when it comes to car maintenance. My husband is deployed and my father lives 500 miles away, so I'm on my own right now. Please be patient with me. I'm learning.

I've replaced the thermostat, the piece on the side of the block, the Y fitting on the back of the head, and the water pump all within the past 4 months, which is when I bought the car at 185,000 miles. I don't know if the radiator has ever been replaced. I took the head to a machinist shop (NAPA) to have it machined down 12/1000 of an inch, so it was perfect when I put the head back on 2 weeks ago. (The guide says you can file 17/1000ths off, so I was within the guidelines)

The car was running when I was filling the expansion tank and the car was parked on an upward incline. I kept filling for 30 minutes hoping that the air bubbles would stop coming out of the vent, but they never stopped coming. At which time, I stopped, closed everything up and came inside and posted my question. Was I supposed to close the vent screw and radiator cap with bubbles still coming out, then drive it around and repeat the process a few times until the bubbles stop coming out? Or am I supposed to wait until all of the bubbles stop coming out, then close it and drive around the block and repeat?

[geetarspaz]

I learned the hard way too : )
Then you really remember "how to" for next time
Best bet, listen to Jess!

[MOTORSPORTti]

i hope do not bother guys!!! i got a issue with mine since 2 months a go the temp is going normal when i drive ./ once i get traffic the temp gauge rise a little to 3/4 and later back to the center that is a issue what i have to do?

[slow_ti]

Sounds like your fans aren't kicking in. Check fuses, relays, and the switch. I don't have much experience with the m44 e-fan. Clutch fan FTW haha

[MOTORSPORTti]

the fan is electric one ..seems working so the temp gauge rise to 3/4 and after the fan starts to working 2 min the temp back to normal .. do u think my fan is begin to get bad?

[cooljess76]

Originally Posted by MOTORSPORTti

i hope do not bother guys!!! i got a issue with mine since 2 months a go the temp is going normal when i drive ./ once i get traffic the temp gauge rise a little to 3/4 and later back to the center that is a issue what i have to do?

Start by BLEEDING THE AIR OUT OF THE SYSTEM. And you say this has been happening for the past two months? FWIW, you should NEVER EVER EVER let the temp needle rise above the 12 o'clock mark. Especially on an engine with over 100k miles on it. Unless you have 2 grand burning a hole in your pocket, shut the engine off and stop driving it until the problem is fixed.

[MOTORSPORTti]

ok my friend ill try that ..thanx

[cooljess76]

BTW, your fan either works or it doesn't. It should run on high speed when you turn the A/C on. It should run at low speed when the coolant temp sensor tells it to kick on. There's a high speed relay, a low speed relay a temp sensor and a fuse. I've seen all of these things fail. Sometimes if the high speed relay fails, the fan will only run in high speed mode. Yes I said high speed mode. The high speed relay has a circuit that gets stuck open and prevents the low speed relay from getting a current. I don't want to go into it here because then a bunch of people are going to start asking questions about it in this thread.

Here:
http://www.318ti.org/forum/showthread.php?t=34064

Here:
http://www.318ti.org/forum/showthread.php?t=34013

Here:
http://www.318ti.org/forum/showthread.php?t=27983

[MOTORSPORTti]

i bleed the car with no problems .. i ve to check the fan speed i think is only high speed is working..thank you so much..

[MOTORSPORTti]

yea my fan working without ac ..temps rise a little right side and once the gauge going back to (center) 12 o'clock (normal) is off again..that happened when the car is idle for long time or traffic. so what do u think?

[MINIz guy]

Okay, I'm going to bump this thread since I have my own question.

I did a coolant flush and bled it properly. Front up on an incline, heat at full, ran the engine and filled until no bubbles came out of the bleed hole. The gauge is just shy of 12 o'clock when fully warmed.

Now, I'm just curious about operating temperatures. Driving down the highway at 70 MPH, A/C on, my coolant temperature hovers around 87-90*C. At stops, I've seen it as high as 96 before I started moving again. Are these normal operating temperatures?

I triggered my auxiliary fan via INPA, so I know that works. What temperature does the fan switch operate at?