Discussion
My 1982 BMW 3 series has a minor cooling issue, the engine temp does not over heat, but it gets warmer than it should (and has done in the past). i've had the radiator flushed about 3 times in the last 2 years, the water pump has been changed, as has the thermostat. basically, the temp should sit on half way on the gauge, but frequently gets near-ish to 3/4. after turning the engine off today i checked the radiator hoses, the bottom hose was cold, the top rad. hose was only lukewarm and the radiator cap was also only lukewarm. does this suggest a radiator blockage or something?
as said, the car doesn't over heat and is perfectly driveable, but it does get me sweating under the collar a bit to see the temp rise a bit too far for my liking.
the temp doesn't go particularly higher in traffic than moving which to me, suggests it's not a thermostat problem, but i could be wrong! the problem has only arisen in the last 6-7 weeks and i can't recall anything that would have caused it. fan belt is also new-ish and has recently be tightened so it's not that. the fan is not electric and is driven off the belt, so not that either.
not much else to an 80's cooling system, so does it sound like radiator problem?
thanks
as said, the car doesn't over heat and is perfectly driveable, but it does get me sweating under the collar a bit to see the temp rise a bit too far for my liking.
the temp doesn't go particularly higher in traffic than moving which to me, suggests it's not a thermostat problem, but i could be wrong! the problem has only arisen in the last 6-7 weeks and i can't recall anything that would have caused it. fan belt is also new-ish and has recently be tightened so it's not that. the fan is not electric and is driven off the belt, so not that either.
not much else to an 80's cooling system, so does it sound like radiator problem?
thanks
annodomini2 said:
Water pump?
sorry forgot to say the water pump was also changed about 3months ago. it was, however, a 2nd hand one but the bearing was very tight and was from an indy specialist, not a scrappy. generally, E21 water pumps, if they fail, it's the bearing which causes them to lose fluid, not the pumping mechanism. the car doesn't appear to be leaking any coolant (certainly not anything significant).it's not a completely sealed system like modern ones so naturally some vapour will escape. it uses about 200-300ml coolant every 600-700 miles which is not excessive. coolant level also fine.
for about 6weeks after changing the water pump, the engine temp stayed bang on half way, just as it should. it's strange!
Edited by E21_Ross on Saturday 8th May 11:48
I don't know thes engines but you say it's a mechancial fan?
Is it directly driven all the time or has it got a viscous coupling? I'm suspecting the later. These couplings should stiffen as they get hot so the fan gets more drive when the engine gets hot. I've seen a few fail so they stay slack & cause this sort of issue.
If the fan is on a coupling you should be able to turn it easy enough by hand with the engine cold, try it again with a hot engine & it should be a lot stiffer.
Is it directly driven all the time or has it got a viscous coupling? I'm suspecting the later. These couplings should stiffen as they get hot so the fan gets more drive when the engine gets hot. I've seen a few fail so they stay slack & cause this sort of issue.
If the fan is on a coupling you should be able to turn it easy enough by hand with the engine cold, try it again with a hot engine & it should be a lot stiffer.
it's even older than that, it is a mechanical fan which is driven all the time (i'll be looking to change it to an electric fan) and the fan belt is tight so it's definitely working. the fact it's not just sitting in traffic when it gets hot says to me it's probably not the fan. could it possibly be something as simple as an air lock??
thing is though which is suggesting it's not even the radiator, was 7-8 weeks ago, the radiator was fine (along with the engine temp in general). why would the radiator suddenly stop working as efficiently?
edit: might try bleeding it later and see, do i just take the rad cap off and run the engine for about 15mins until it's up to temp, then switch the heater on full. would that help get some air out?
thing is though which is suggesting it's not even the radiator, was 7-8 weeks ago, the radiator was fine (along with the engine temp in general). why would the radiator suddenly stop working as efficiently?
edit: might try bleeding it later and see, do i just take the rad cap off and run the engine for about 15mins until it's up to temp, then switch the heater on full. would that help get some air out?
Edited by E21_Ross on Saturday 8th May 14:05
Running it up to temp with the heater on should help yup.
I'd be considering taking the rad out & back flushing it, it's possible all that work on the cooling system has dislodged something which is partly blocking the flow. Your comment the bottom of the rad still felt cool supports this a bit.
I'd be considering taking the rad out & back flushing it, it's possible all that work on the cooling system has dislodged something which is partly blocking the flow. Your comment the bottom of the rad still felt cool supports this a bit.
I would try another thermostat. Just because the problem is not worse in traffic does not mean the thermostat is fine. An idling engine only produces a tiny amount of heat compared to one working hard, but normaly when working hard you have a good cooling air flow.
A cold bottom hose suggests not very much circulation.
You have ruled out the rad and water pump, so I would go for the thermostat next.
A cold bottom hose suggests not very much circulation.
You have ruled out the rad and water pump, so I would go for the thermostat next.
Check coolant level when cold.
Start engine & allow run up to temp.
Keep checking the top hose this hose should suddenly get hot as the stat opens & allows full flow into the top of the rad. If it gradually warms up either the stat is defective - stuck open - or missing. This interferes with the coolant circulation.
Is the correct stat fitted? Many cheap pattern ones are rubbish - can be completely wrong - & as with all critical parts you are best buying the genuine one from the dealer (Yes, I know it tends to be expensive but at least you know the part is correct spec!)
Does the rad have any cool or cold areas? These would signify blockage(s).
Flushing may not remove blockages or the build up of silt over time.
Is the rad original? Are all the fins in good condition? I recently replaced the rad on my RRC & was rather surprised at the difference in weight between old & new!
Is the temp sender faulty? Mine eats one every couple of years & the gauge starts reading high.
Start engine & allow run up to temp.
Keep checking the top hose this hose should suddenly get hot as the stat opens & allows full flow into the top of the rad. If it gradually warms up either the stat is defective - stuck open - or missing. This interferes with the coolant circulation.
Is the correct stat fitted? Many cheap pattern ones are rubbish - can be completely wrong - & as with all critical parts you are best buying the genuine one from the dealer (Yes, I know it tends to be expensive but at least you know the part is correct spec!)
Does the rad have any cool or cold areas? These would signify blockage(s).
Flushing may not remove blockages or the build up of silt over time.
Is the rad original? Are all the fins in good condition? I recently replaced the rad on my RRC & was rather surprised at the difference in weight between old & new!
Is the temp sender faulty? Mine eats one every couple of years & the gauge starts reading high.
right guys, little update:
went to the car, removed rad cap, started engine and allowed to idle for 15mins or so until it reached operating temp. some coolant went into the overflow pipe and drained out. turned heaters on full as well as fans and coolant level dropped. allowed to run for a few more mins. turned engine off.
there are 3 "main" hoses:
1 - from engine to top of radiator
2 - from engine to thermostat "inlet"
3 - from thermostat "outlet" to bottom of radiator.
hoses 1 and 2 were hot, hose 3 was cold. this suggests to me the thermostat is not opening? though i could be totally wrong as i'm not that mechanically minded.
the top of the radiator was hot to the touch, but around the bottom and middle it was cold.
the thermostat in my car is under 4 months old and is an official BMW one, thermostats are known problems on these cars, and BMW don't make them any more, they are just old stock. chances are this thermostat has been sitting on a shelf for 10-15 years.
the radiator seems (by service history) that it was changed approx 17-18 years ago, when the car was about 10 years old
can't see any other file stating another radiator has been changed.
in the last 2 years, the radiator has been flushed about 3 times.
does this help any more into a conclusion?
thanks fellas, it's really appreciated!
went to the car, removed rad cap, started engine and allowed to idle for 15mins or so until it reached operating temp. some coolant went into the overflow pipe and drained out. turned heaters on full as well as fans and coolant level dropped. allowed to run for a few more mins. turned engine off.
there are 3 "main" hoses:
1 - from engine to top of radiator
2 - from engine to thermostat "inlet"
3 - from thermostat "outlet" to bottom of radiator.
hoses 1 and 2 were hot, hose 3 was cold. this suggests to me the thermostat is not opening? though i could be totally wrong as i'm not that mechanically minded.
the top of the radiator was hot to the touch, but around the bottom and middle it was cold.
the thermostat in my car is under 4 months old and is an official BMW one, thermostats are known problems on these cars, and BMW don't make them any more, they are just old stock. chances are this thermostat has been sitting on a shelf for 10-15 years.
the radiator seems (by service history) that it was changed approx 17-18 years ago, when the car was about 10 years old
can't see any other file stating another radiator has been changed.in the last 2 years, the radiator has been flushed about 3 times.
does this help any more into a conclusion?
thanks fellas, it's really appreciated!
annodomini2 said:
So your pump is working.
Take the thermostat out and test it in a jug of boiling water.
i have no tools with me here at uni at the moment Take the thermostat out and test it in a jug of boiling water.
how annoying. don't have to drive the car much, but i do have a 150 mile trip in 2 weeks to get home. after then, i can investigate more.think i might change both radiator and thermostat. radiator is ancient and could probably do with replacing. it sounds like a thermostat issue to me...the fact that the hose coming from the rad to thermostat (bottom hose) is cold. but then, a lot of the radiator is also cold, suggesting not much flow so rad might be blocked.
who knows, could be a combination of the 2?
grrrrrrrrrrr so annoying!!
Hooli said:
Take the rad out, turn it upside down & put a hose in the outlet. Watch the s
te pour out the other end. Then swop the flow around.
Repeat until the water comes out clean & put it all back together.
this was only done in january te pour out the other end. Then swop the flow around.Repeat until the water comes out clean & put it all back together.
surely it shouldn't need it doing again.i'm getting fed up with cooling problems on this car. only once has it been bad enough for me to turn the engine off (was getting towards the red....that was failed/leaking water pump) but now it doesn't go above 3/4, but it still shouldn't get that hot. so might just replpace both rad and thermostat.
been offered a 2nd hand radiator which has done under 1000miles. the guy owns an E21 race car with 190bhp ish and said the original rad (same as my car!!!) can't cope with that much extra power so he just wants rid.
should i go for it, or get a new one?
cheers again fellas, the help is really appreciated. any further input is too
Don't leave the cap off when doing any checking. That's not how the system usually works is it.
If everything else has been replaced & is in good working order then that only really leaves the ancient radiator.
With a used one you have no real idea whether its any better than the old one.
As I've already said, flushing may not work, especially if any of the radiator sealants have been used at any time in its life.
If everything else has been replaced & is in good working order then that only really leaves the ancient radiator.
With a used one you have no real idea whether its any better than the old one.
As I've already said, flushing may not work, especially if any of the radiator sealants have been used at any time in its life.
Edited by paintman on Saturday 8th May 22:39
I'd check the thermostat first, worst case you have to leave it out until you have opportunity to fit another.
Raid poundland or one of the cheap shops in town for a simple budget socket or spanner set, most thermostats of that era are 8 or 10mm bolts
If the thermostat works its the rad, if not you have the thermostat out to replace it, if they're no longer made by BMW sounds like it may be beneficial to get an after market unit.
If you have a haynes manual it should specify the full open temperature of the thermostat.
With the new stat and jug of water and thermometer slowly increase the temperature of the water until it opens, the thermometer will tell you the temperature.
If the thermostat works, then do you trust this individual with the rad?
Raid poundland or one of the cheap shops in town for a simple budget socket or spanner set, most thermostats of that era are 8 or 10mm bolts
If the thermostat works its the rad, if not you have the thermostat out to replace it, if they're no longer made by BMW sounds like it may be beneficial to get an after market unit.
If you have a haynes manual it should specify the full open temperature of the thermostat.
With the new stat and jug of water and thermometer slowly increase the temperature of the water until it opens, the thermometer will tell you the temperature.
If the thermostat works, then do you trust this individual with the rad?
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