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DISCUSSION => Engine + Driveline => Topic started by: HarrisonS on March 19, 2007, 02:34:32 PM

Title: Cooling Problem
Post by: HarrisonS on March 19, 2007, 02:34:32 PM: Hey guys,

I just got a 1991 318is about 3 months ago, and it has been running great. But about week ago i noticed it was running a bit hot (3/4 mark) and then in the last couple days it has been completely overheating (hitting the red). It seems to be slowly losing water, although I cannot see where the leak is. I have refilled it with water and drove it around a bit and it still overheats within a mile or so. When I turn on the heat, cool air comes out of the vents. I also checked the oil and there is no water or coolant in it. Any ideas? Bad thermostat?
Title: Cooling Problem
Post by: e9nine on March 19, 2007, 02:57:01 PM: Welcome!

Be careful at this point as a warped head/blown headgasket could be lingering around.

I'd say to let the car sit at idle for a couple of minutes with the hood open, pay attention to the vital locations; hoses, water pump, thermostat housing, radiator and try see if any leaks pop up.

I'll let others chime in on extra tips...
Title: Cooling Problem
Post by: asubimmer on March 19, 2007, 03:01:15 PM: sounds like you tstat is stuck closed. it could be the water pump though.
Title: Cooling Problem
Post by: HarrisonS on March 19, 2007, 03:16:58 PM: I've been keeping an eye on the leak for the past couple days and it seems as if some days it leaks more than others. Yesterday, with a cold engine I started it up and let it run and I could see no leaks or water dripping, but later that day I drove it about a mile to see what it would do, and when I got back to my house it was low on water, and so I filled it again and didn't drive it. This morning I looked at it and it was low again, but there wasn't a whole lot of water on the ground
Title: Cooling Problem
Post by: e9nine on March 19, 2007, 03:25:30 PM: We need to identify the source of the leak now that we know it leaves a trace... I'd avoid driving the car if I was you at this point. Our aluminum heads warp easily
Title: Cooling Problem
Post by: gearheadE30 on March 19, 2007, 03:36:21 PM: Sounds to me like something is clogged, and the pressure is probably pushing it out of a crack in a line. If it isn't leaving a trail, look near hot items, i.e. headers, which could cause the water to evaporate quickly. I have no idea if any cooling lines run near there though...

tstat is probly the best bet, my family's E34 had a bad one, with similar symptoms

good luck, hope it's nothing serious
Title: Cooling Problem
Post by: HarrisonS on March 19, 2007, 05:34:07 PM: How hard is it to replace the tstat? Do I need any special tools?
Title: Cooling Problem
Post by: e9nine on March 19, 2007, 05:41:43 PM: Quote from: HarrisonS;21701
How hard is it to replace the tstat? Do I need any special tools?

Luckily the thermostat is one of the articles on our very own "Zoso's" site

http://zoso.no-ip.org/cars-318i.html
Title: Cooling Problem
Post by: Tonyb on March 20, 2007, 01:48:27 AM: Make sure you bleed the radiator!
Title: Cooling Problem
Post by: Choking Hazard on March 20, 2007, 07:48:16 AM: Removing the fan shroud makes t-stat replacement MUCH easier. What is the proper torque spec for the housing?
Title: Cooling Problem
Post by: HarrisonS on March 20, 2007, 01:19:00 PM: I am confused on what all is involved in "bleeding" the system. Are there more steps than just emptying all the coolant from the engine and the radiator?
Title: Cooling Problem
Post by: e9nine on March 20, 2007, 03:25:31 PM: Quote from: HarrisonS;21816
I am confused on what all is involved in "bleeding" the system. Are there more steps than just emptying all the coolant from the engine and the radiator?

Yes there's a bleed screw used to relieve pressure gradually so air bubbles/pockets aren't in the cooling system.

Here's an excerpt

[SIZE=+1]Bleeding[/SIZE] Radiator mounted expansion tank:
1. Loosen the bleed screw on top of radiator expansion tank and let the coolant flow out as you pour it in the reservoir. Tighten the screw when the flow out is free of air bubbles.
Separate expansion tank:
1. Loosen the bleed screw on top of thermostat housing and let the coolant flow out as you pour it in the reservoir. Tighten the screw when the flow out is smooth and free of air bubbles.
2. Set the temperature setting to full warm and start engine.
3. When the car is going to reach his normal temperature you might going to need to add more coolant. Always check the coolant level.
4. With engine idling at normal temperature, open the bleed screw and tighten it when coolant is spilling out smoothly and free of air bubbles.
5. Repeat bleeding, and again and again.
6. Do it a few times to avoid overheating.
Title: Cooling Problem
Post by: Choking Hazard on April 05, 2007, 10:44:29 PM: The "bleeeding" is different from "flushing". Bleeding is just done at the end to get out air bubbles. If you read the above thinking "flushing", it sounds like you do this to add new coolant.
Title: Cooling Problem
Post by: BrandC on April 05, 2007, 11:38:19 PM: You can do a leak down test as well if you suspect coolant leaks. This is just a mock radiator cap that can be pressurized with air to simulate pressure in the coolant system. If you see anything leak, that's your culprit.

If there are no leaks on the leak down system, you probably have air in the coolant system.
Title: Cooling Problem
Post by: rhogg on April 06, 2007, 01:11:57 AM: The first thing to do before you start pulling things apart is to try to find the leak. At idle you might not be able to see the leak. Rev the engine and pay close attention to the top passenger side hose. A cracked rad neck is common.