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skanders View Drop Down
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Direct Link To This Post Topic: BMW 320I OVERHEATING
    Posted: 12-July-2005 at 11:05
Hi guys and gals  I hope that someone may be able to help me my bmw320i  overheated yesterday  and shutdown with  the  expansion  tank  bubbling  and  coolant streaming out of the  bleed hole  I have  since then  tried to solve the problem but have so far failed,

1. I flushed the rad and checked all the pipes ,flushed the engine 
and cooling system  but it has thus failed  to work  if the car is stationary  it  will sometimes  be  ok  and  temp gauge stay in the middle but if i accelerate it starts to overheat and will gradually  go into the  red zone very  quickly.

2. I have noticed that after i have stopped there is a hissing noise from the bleed screw and that the screw does not screw in properly and keeps turning when you screw it, would the bleed screw with not being on properly make the coolant level go all the way to the top.

please can someone help  me i think it is the bleed screw but would like someone to confirm  that if pressure is escaping from the bleed screw it would make the car overheat.

PS:-  im pretty sure that the bleed  screw has been like this for a while the car did get hot before but when  i sped up it would easily cool  off but now it does not it may be the fact that the car has got so hot that it finally discovered that the bleedscrew is weak.

also where the bleed screw goes in right at the bottom near the hole there is a gap to one side of it i can put my screw driver right through it is that normal.

your help  is appreciated.
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dazza28 View Drop Down
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Direct Link To This Post Posted: 12-July-2005 at 12:54

Hi,

It sounds to me like 1 of 2 things. Firstly it could be the water pump. As I understand it, a lot of them had plastic impellers that would eventually over time loose grip on the shaft. So whilst the engine was going faster the coolant wasn’t which leads to quick over heating. The second thing it could be is the thermostat. Which is failing to open correctly and not allowing a sufficient flow of water through the radiator.

As a precaution for any car that has over heated, it is always wise to change the thermostat as they can loose there efficiency after being toasted.

As for the bleed screw, there only a few pence from the local dealers. I wouldn’t be too confident on blaming it all on that though as it may have been damaged when the car over heated. The hissing sound your hearing is most likely air/water escaping from the expansion cap, as to not let the system get so pressurized it blows a hose off!!

Hope that helps a bit

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Direct Link To This Post Posted: 12-July-2005 at 13:06
Have a look through the cars history, if the water pump has not already been changed out, i would recommend getting it changed (regardless of whether it has caused the fault or not) As the old pumps have plastic impellars which break up. This happened to my 320, caught it in time thankfully.....
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Direct Link To This Post Posted: 12-July-2005 at 13:15
Dazza 28 the hissing sound is definately  coming from  where the bleed screw is  air and water is escaping from that  and the coolant in the expansion tank rises dramatically .

Anyway first things first i am gonna try the bleed screw see if makes a difference and then go for the thermostat

thanks for the help so far
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Direct Link To This Post Posted: 12-July-2005 at 16:29
Tested the thermostat and it opens and closes fine so it is not at fault.

I have not got round to getting the water pump out i will probably do this tomorrow.

But before that I will give the car a good flushing and then try the new bleed screw and see what happens you never know it might jus be that.

cheers. 
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Direct Link To This Post Posted: 12-July-2005 at 17:07
Make sure you get a new bleed screw as they are pennies, as the system is not under pressure it will not work efficiently, hence the water and air loss.
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Direct Link To This Post Posted: 12-July-2005 at 18:00

IMO it is definately the bleed screw. All coolant systems work under pressure. If the system cannot pressurise, the water will boil. If the screw wasn't a good fit then the pressure would have finally got to it as the housing is only alloy. You said you were also losing coolant at the bleed screw, that just adds to the problem with less water in the system causing air locks and with the hot weather, it all adds up. You may need to drill the housing and use a bigger screw if the hole is no longer round.

I would start with obvious bad screw and make sure you bleed the system fully when filling back up and watch the gauge and more than three quarters it's overheating. You need to be real careful 'cause the alloy head on the small six is prone to warping or cracking if it overheats too much then it's an expensive fix!!

Rob



Edited by Madrab
1990 E3o 325i Touring and she's definately a she! Pain in the ass sometimes but goes like a bunny :oD
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Direct Link To This Post Posted: 13-July-2005 at 04:25

I can see on the screw that some ridges are worn im not sure but dont the screws come in one size or can you get bigger ones, also if the new one dont fit what would you advise me to do then.

 

 

 

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Direct Link To This Post Posted: 13-July-2005 at 17:34
Well guys  i  put in the bleed screw and it didnt come out but now i have a  different  problem  at  idle the needle  stayed in the middle  so  i decided  to  take it for a  spin  5 mins  gone and it seemed fine and then the needle  started to  again  got cold air from the blowers  but no warm air  so i then got home  and opened the hood and their was a  whining noise which i think was coming from the  thermostat  or the fan  couldnt work out which also there was a bit of smoke from the fan area.

Its either the thermostat has had it although the test ran fine or i didnt tighten the housing enough.

the coolant went near the top as it normally would do but it was not very warm.

any suggestions.
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Direct Link To This Post Posted: 14-July-2005 at 09:13

Skanders,

pretty hard to work out with what you have detailed. You can remove the thermostat for these tests to rule it out by the way.  It does sound like the system has an airlock though.When you refilled the coolant and then started the car, was the heater on hot with the blower on and then you released the trapped air through the bleed screw until only fluid escapes, and the heater is blowing hot? Then top up.

You mentioned about smoke and a whining noise now? The noise sounds potentially like the viscous coupling on the fan (known failure point) , or potentially the pump bearing, no idea on the smoke tho unless something is burning in the heat.

Rob

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Direct Link To This Post Posted: 14-July-2005 at 09:57

Get a new water pump mate. It defiantly sounds like that's too blame

Get a new stat aswell just to be on the safe side. Go to somewhere like GSF or ECP for the pump. Should only be around £40 IIRC



Edited by dazza28
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Direct Link To This Post Posted: 15-July-2005 at 06:39
Hi guys  checked the water pump and it looks fine  no damage i think that it is an  air lock in the system somewhere because if i  pour coolant into the  tank  coolant with  bubbles  comes out of the  bleed hole  and does not run clear  definately not a  head  gasket  as the car runs  fine  and hav not noticed anything that relates to  that  question is whats the  best way  to  vent it.

thanks so far.
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Direct Link To This Post Posted: 15-July-2005 at 07:18
With the engine warm, heater full hot, and expansion tank cap off (very slowly!!) Try repeatedly squeezing the top hose. This used to work a treat on my 318
Mark
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Direct Link To This Post Posted: 15-July-2005 at 08:14

The way I bleed the system is as korky has said above but run engine with the bleed screw loosened and the cap off from cold, heater on hot and keep adding water while raising the rpm a little to raise the water pressure till there is no more air escaping from the bleed screw, only water. This can sometimes take quite a while. Once there is no air escaping, lock off the screw then raise the revs to about 3k and run like that for a minute just to let the water pressure force out any other air, watching the temp gauge of course, and return to idle and then loosen the screw again to check for air. If you do it straight from hot the water will expand so when it cools down again the level will not be correct and can sometimes draw air back into the system.

Rob



Edited by Madrab
1990 E3o 325i Touring and she's definately a she! Pain in the ass sometimes but goes like a bunny :oD
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Direct Link To This Post Posted: 15-July-2005 at 16:41
Ok guys  cracked it  it was the  thermostat after all turns out that sometimes it opened and sometimes it didnt.

so theres no thermostat in there at all now but the car is not overheating.

Anyway as im very inexperienced in cars can you tell me what the thermostat does anyway.

cheers.
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Direct Link To This Post Posted: 15-July-2005 at 19:06

The Thermostat simply controls the amount of water that flows through the radiator to keep the ideal operational temp.

So it is fully closed when the engine is cold so it can heat up quickly and gradually opens up to allow the coolant in the block to flow round the radiator. It will open and close at varying degrees depending on speed, engine rpm, and ambient temp to keep the temp gauge bang in the middle.

Sounds like in your case it just wasn’t opening enough. A word of advice, get a new one from the dealers as there a lot better and more reliable than the aftermarket ones you would get in halfords or somewhere similar!

P.s. when you looked at your water pump did it have a plastic or metal impeller?

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Direct Link To This Post Posted: 15-July-2005 at 19:09
It had a  plastic impeller but the  pump was  sound  good as new  another thing  is it  ok to run the car as is for the moment as i have the  thermostat ordered  from  euro car parts and it wont be here till  monday or tue.

thanks mate.
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Direct Link To This Post Posted: 15-July-2005 at 19:26

Should be OK to run without the thermostat as a temporary measure. It will just take a long time to heat up and wont be running at its peek operating temp. Certainly no danger of over heating!

Seriously though, I would really consider changing your water pump for a metal impeller one. There a well known failer point. but its up to you...

 

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Direct Link To This Post Posted: 16-July-2005 at 08:31

Hi guys while coming to work the car was fine temp gauge slap bang in the middle on the motorway but when i hit traffic and came to a standstill the car started to overheat again.

But this time instead of overheating while accelerating it cools down the faster i go it cools itself off.

Any ideas to what it could be definately the thermostat is shot so i have ordered a new one do you think that the fan may need replacing as well as i only think that this is causing the fault now.

please advice the car runs perfect so it cant be the head gasket.

thanks.

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Direct Link To This Post Posted: 16-July-2005 at 11:53

Did the fan test rolled up a bit of news paper and put it in the fan it did not shred it the paper jus flapped about and stopped the fan.

I think im gonna go with a new coupling which i think will finally put the overheating issue to rest.

thanks.

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