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View Full Version : Cooling issue (tstat?)


Redster
02-16-2008, 04:06 PM
This morning I got check coolant message, so I added some (about 1L) but soon after that message came back, when I checked coolant level I saw it was low again.

I know it's leaking now, but for some reason heat doesn't work all the time; it'll blow hot air for a while then cold, then hot..

Would this be a way for the engine to cool itself or it's something else?

As far as overheating, engine temp stays put (just bellow half) then it goes up, almost to the red, but before reaching it it'll come down (all this in 10-15 seconds).

I just hate how it's impossible to find a good mechanic that's open late/on weekends so I'm stuck till Tuesday..

Arash
02-16-2008, 04:23 PM
thermostat

I just got mine fixed. same symptoms. its nice to have steady heat again!

Redster
02-16-2008, 04:26 PM
thermostat

I just got mine fixed. same symptoms. its nice to have steady heat again!

Ok I guess that makes sense..it's just that i had mine changed about 8 months ago.

Any way coolant can leak if thermostat is faulty? I know for sure I'm loosing coolant so it'd be nice to connect the two problems..

Arash
02-16-2008, 04:32 PM
Ok I guess that makes sense..it's just that i had mine changed about 8 months ago.

Any way coolant can leak if thermostat is faulty? I know for sure I'm loosing coolant so it'd be nice to connect the two problems..

I was loosing coolant too for some odd reason, changed thermostat, problem fixed.

Redster
02-16-2008, 04:35 PM
Thank you, that makes me feel better now:)

How much/fast were you loosing? In my case I think I lost 1.5-2L pretty fast (twice) but that's all, once that goes out I'm not loosing any more of it

Arash
02-16-2008, 06:45 PM
Thank you, that makes me feel better now:)

How much/fast were you loosing? In my case I think I lost 1.5-2L pretty fast (twice) but that's all, once that goes out I'm not loosing any more of it

yeah I topped it off 2 times before I got it fixed. still don't know where that coolant was going, I didn't see any leaks.

bimmerjoe
02-16-2008, 07:09 PM
I just recovered fromalot of cooling system problems.. my needle was doing the same as yours going from just under the middle then would shoot to the red, and the heat would go from hot to cold, exact same symptoms so i replaced the thermostat and that was fixed no coolent leaking. then my expansion tank blew up and that was that... if your leaking coolent it could be 1 of 4 things. 1 of your hoses, your waterpump, your rad, or your expansion tank which is the coolent resovour...the hoses and the tank are the cheapest..

Redster
02-16-2008, 07:35 PM
I replaced the expansions tank and one hose about 4 months ago, water pump was replaced as well. I'll know for sure when i get it to a mechanic but I'm thinking now that it's thermostat.

Redster
02-16-2008, 07:41 PM
I just remembered something, a while ago I had a coolant leak and I thought it was another hose but my mechanic found out that a rubber band (have no idea what's the name of the part) had to be replaced..so he had one same size/thickness and he put in, checked the pressure and no leaks. I guess I can check that too..

bimmerjoe
02-16-2008, 07:52 PM
it doesnt make sense that the thermostate would be leaking?? a thermostate doesnt leak?:confused:

BigD
02-16-2008, 07:54 PM
I don't get it, how do you lose coolant with a bad thermostat? It's a closed system. The thermostat is just a valve, either keeping the coolant in the engine or letting it circulate through the radiator and back in. The only symptoms are a car that takes long to warm up or a car that overheats. If you're losing coolant it's either going on the floor or into your oil pan (or your interior) because of a leak, a busted head gasket or heater core.

If I'm wrong, someone please explain how it's possible.

Redster
02-16-2008, 08:04 PM
What is the part right under the expansion tank, plugged into one of the hoses?

That's where a rubber band was changed because I was loosing coolant there..then it was fine for a while, before I had to add more coolant (about 1/2l in 3 weeks)..I think it's leaking there again.

Any idea what size/thickness rubber band I should use there?

I guess I'm loosing coolant there, but the thermostat still has to be replaced because of that cold/hot air issues..

bimmerjoe
02-16-2008, 08:10 PM
try to find a picture of what your trying to show us. and what type of car is it?

Redster
02-16-2008, 08:13 PM
It's 99 540i

That part is right under expansion tank plugged into one of the hoses, about 5-6cm "tall"

I'll try to find a picture online

Redster
02-16-2008, 08:16 PM
Ok it's where the arrow is pointing (a bit more to the left, passenger side), all the way down plugged into a hose..

http://img239.imageshack.us/img239/3817/3523enginebigia7.jpg

bimmerjoe
02-16-2008, 08:26 PM
i have no idea bro.. but it doesnt sound expensive. if i were you i wouldnt drive the car till tuesday

Arash
02-16-2008, 08:49 PM
I don't get it, how do you lose coolant with a bad thermostat? It's a closed system. The thermostat is just a valve, either keeping the coolant in the engine or letting it circulate through the radiator and back in. The only symptoms are a car that takes long to warm up or a car that overheats. If you're losing coolant it's either going on the floor or into your oil pan (or your interior) because of a leak, a busted head gasket or heater core.

If I'm wrong, someone please explain how it's possible.

Actually on second thought, I do suspect its ending up in my oil pan, the oil looks a bit diluted on the stick and looks like its sitting too high. Changing the thermostat definitely helped get the heat back and the motor doesn't overheat anymore. how can I know if coolant is mixing with the oil?

myndgone
02-17-2008, 12:06 AM
expansion tank

Redster
02-17-2008, 12:54 AM
expansion tank

I changed it before..and I really can't see the leak now.

Also, only about 1.5-2L of coolant leaks, then it stops..that's why I think it's that rubber band (that part on the bottom), so once enough coolant leaks pressure goes down and leaking stops..

Euro_E30
02-17-2008, 03:15 AM
check if you chamber plate is leaking, take the engine cover off, and look at the back of the motor on the transmission side and see if there is any coolant leaking, and on the front where the throttle body is. seen this problem many times. i work late nights doing side jobs, let me know if u need anything*th-up*

BigD
02-17-2008, 10:28 AM
Actually on second thought, I do suspect its ending up in my oil pan, the oil looks a bit diluted on the stick and looks like its sitting too high. Changing the thermostat definitely helped get the heat back and the motor doesn't overheat anymore. how can I know if coolant is mixing with the oil?

Various ways, including signs of coolant on your dipstick or if it's really bad, unnaturally large volume of white smoke (steam) from the exhaust. Open the overflow tank and run it, see if you can hear bubbling inside (may have to warm up first). Ask Polski, he should be able to tell, where is he anyway, I haven't seen him online in ages and his voicemail is full...

Here's a vid I took of a 635 with a blown HG.

<object width="425" height="355"><param name="movie" value="http://www.youtube.com/v/m6yLsx2nb24&rel=1"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/m6yLsx2nb24&rel=1" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed></object>

Here's a really bad one:

<object width="425" height="355"><param name="movie" value="http://www.youtube.com/v/g_ypaiiWcag&rel=1"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/g_ypaiiWcag&rel=1" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed></object>

Redster
02-17-2008, 11:55 AM
Ok looks like the part I was trying to describe/locate is the temperature sensor..last time coolant leaked there because the rubber band on it (side that goes in) was bad, so I put on a new one that was very similar to the original, but not from a dealer.

Does any of this make sense?:)

Redster
02-17-2008, 01:46 PM
Better yet, does anyone know proper size for that rubber band?

Arash
02-17-2008, 02:40 PM
Various ways, including signs of coolant on your dipstick or if it's really bad, unnaturally large volume of white smoke (steam) from the exhaust. Open the overflow tank and run it, see if you can hear bubbling inside (may have to warm up first). Ask Polski, he should be able to tell, where is he anyway, I haven't seen him online in ages and his voicemail is full...



Thanks for the info.

Polski's mom is away so he's been busy taking care of the siblings, and the business. Last I saw him was 2 weeks ago.

Redster
02-19-2008, 03:49 PM
It looks like head gasket issue right now, I'll know more once they take it apart.