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Discussion Starter #1 (Edited)
hi guys, basically this is my problem (if i have one) as the car is runnig at temp as it should
letting my car idle the temp gauge would go upto halfway and the heater would be hot. GOOD TIMES!
start drivin the gauge would drop pretty quick to just above the blue mark giving just warm air from heater. BAD TIMES!

i read the net saying its an airlock in heater core.

just bought the car and with this cold weather decided to change coolant.
so changed coolant and bled system over 2/3 days up on ramps ect, but car still had the same problem as above.

so i decided to change the thermo (its the 1 with the plastic housin-£40.50p)
removed hoses off old thermo
removed fan cowling
didn't remove fan as i couldn't undo nut after 30mins of trying
so i unbolted old thermo and wiggled it past fan blades carefully but dead easy (took 30 secs) so no need to remove fan at all!
fitted new genuine BMW thermo with housing
put the coolant back that had drained
temp gauge is now stayin halfway when drivin an heater is hot, GOOD TIMES!
however top hose is HOT n bottom hose is COLD, BAD TIMES!

i began to remove bottom hose thinkin airlock but coolant came out straight away

so thats where i am now -the car is running fine, the heater is blowin hot, the temp stays halfway when idling n drivin, no drop in temp- you wouldn' know there was anythin wrong apart from the cold bottom hose. should it be cold?

ps. i did read that the cooling system on BMs are that good that the bottom hose should be cold (but that was a yank forum)

any feedback on this will be appreciated as i'm going out again into the freezin cold to try bleedin system AGAIN. BAD TIMES!
 

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hi guys, basically this is my problem (if i have one)
letting my car idle the temp gauge would go upto halfway and the heater would be hot. GOOD TIMES!
start drivin the gauge would drop pretty quick to just above the blue mark giving just warm air from heater. BAD TIMES!

i read the net saying its an airlock in heater core.

just bought the car and with this cold weather decided to change coolant.
so changed coolant and bled system over 2/3 days up on ramps ect, but car still had the same problem as above.

so i decided to change the thermo (its the 1 with the plastic housin-£40.50p)
removed hoses off old thermo
removed fan cowling
didn't remove fan as i couldn't undo nut after 30mins of trying
so i unbolted old thermo and wiggled it past fan blades carefully but dead easy (took 30 secs) so no need to remove fan at all!
fitted new genuine BMW thermo with housing
put the coolant back that had drained
temp gauge is now stayin halfway when drivin an heater is hot, GOOD TIMES!
however top hose is HOT n bottom hose is COLD, BAD TIMES!

i began to remove bottom hose thinkin airlock but coolant came out straight away

so thats where i am now -the car is running fine, the heater is blowin hot, the temp stays halfway when idling n drivin, no drop in temp- you wouldn' know there was anythin wrong apart from the cold bottom hose. should it be cold?

ps. i did read that the cooling system on BMs are that good that the bottom hose should be cold (but that was a yank forum)

any feedback on this will be appreciated as i'm going out again into the freezin cold to try bleedin system AGAIN. BAD TIMES!


Personally dude....................If the heaters are working, cars not over heating at idle or on long journeys- dont worry about.

from what you've said- all seems fine mate..................but is the hose "Cold" cold or not quite as hot as the top?
 

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Discussion Starter #3
Personally dude....................If the heaters are working, cars not over heating at idle or on long journeys- dont worry about.

from what you've said- all seems fine mate..................but is the hose "Cold" cold or not quite as hot as the top?
bottom hose is "COLD" cold, no warmth at all. top is "HOT" hot.
i didn't think it should be that cold if its mixing thru the engine.

cheers for the v quick reply
 

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bottom hose is "COLD" cold, no warmth at all. top is "HOT" hot.
i didn't think it should be that cold if its mixing thru the engine.

cheers for the v quick reply

mmh......that is strange dude..........whats the longest you've have driven the car since the thermo change?

Also, if you remove the expansion bottle cap and have the cra reved up a little- does coolant shoot through the return at the kneck?
 

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Discussion Starter #5
mmh......that is strange dude..........whats the longest you've have driven the car since the thermo change?

Also, if you remove the expansion bottle cap and have the cra reved up a little- does coolant shoot through the return at the kneck?
sorry been outside freezin my nuts off!

car ran for an hour last night which inc a 20 mile drive,
car now running at halfway temp, heater hot,
car idling - slight trickle,
speed up to 2500rpm coolant shoots across expansion neck,
bottom hose still cold.

are you supposed to be able to remove expansion cap when at temp without overflowing as im sure i could yesterday.
 

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The lower hose will be cold until the thermostat opens(approx 88.C or 92.C depending on thermo) and lets the coolant flow through the radiator and back into the engine, if it stays permanently cold(even after ragging it round non stop all day) then you have a circulation problem.
 

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are you supposed to be able to remove expansion cap when at temp without overflowing as im sure i could yesterday.[/QUOTE]

I would'nt try that dude, not when the car is hot!!
 

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Discussion Starter #8
The lower hose will be cold until the thermostat opens(approx 88.C or 92.C depending on thermo) and lets the coolant flow through the radiator and back into the engine, if it stays permanently cold(even after ragging it round non stop all day) then you have a circulation problem.
just got back after giving car a run of 12 mile, temp gauge is upto halfway, top hose hot, bottom hose cold and i removed expansion cap without any danger of it gushing out or even overflowing.

its on ramps at the moment, recycling coolant back into expasion tank but no bubbles are coming out. must be an airlock somewhere that will find its own way out. as its still running OK fine,

if i have an airlock and/or a circulation problem am i in danger of causing damage to engine as long as temp stays halfway?

if its not circulating properly would the heater still get hot?

if theres an airlock wouldn't it overheat?

which way does the coolant circulate?
 

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Run the car up while stationary, keep a eye on the temp gauge every so often and feel the lower hose, let us know if it gets hot

if the temp gauge is staying put when driving then your thermo problem is fixed
 

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Discussion Starter #10 (Edited)
update!
i think im getting somewhere, i couldn't get anymore bubbles out by adding coolant so i got a thick broom handle and pushed it into the expansion tank this forced some bubbles out of bleed hole (seems to be working), the bottom hose i getting slightly warmer (dont know whether its cus ive been holding it so long) going back out to try again , will keep you posted - bbbrrrrrrrr!
 

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Discussion Starter #11 (Edited)
i think we've done it! thanks
bottom hose is now warm, GOOD TIMES
nowhere near as hot as the top hose tho,
i can still remove expansion tank cap without worrying about pressure, BAD TIMES
do you think it may be the cap, il try another asap
 

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The O rings on the car do flatten out over time so it would be worth changing the cap as it won't be long before it's knackered if it is the original
 

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Discussion Starter #13
'borrowed' an expansion cap n took car out for a good run, consisting of 10 mile motorway n 13 mile fast country lanes. checked hoses when i got to milford-bottom hose HOT and really firm/pressurised.(unlike when hose was cold it was squidgy) top hose VERY HOT. undid bleed screw slightly n bottom hose lost its firmness but remained hot.
i did the return journey back home and checked again -hot firm bottom hose.

the thermo operates at 95c so perhaps thats why bottom hose stays cold for so long,

i can still remove the expansion cap without worry of it overflowing. is this normal? maybe this cap isn't 100% in holding pressure but better than my original one
 

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Sounds like you are fixed then, it's holding pressure, just keep a eye on the water level over the next week as it may settle :thumbsup
 

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Discussion Starter #15
:applause big thanks to Slacker-ray 'n' Ronnie for your time 'n' help :thumbsup
 
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