Overheating trouble after replacing upper radiator hose assembly

[AlexisR]

Hello,

I have a 1999 323i. Couple weeks ago i noticed that the yellow radiator warning light started to come on. Soon discovered pretty bad leak where the upper radiator hose connects to the radiator itself. A friend helped me with replacing this radiator hose assembly.

Now the radiator warning light stopped. But the car would overheat after just maybe 5-8 mins driving. A friend helping me mentioned problems that can be caused by pockets of air that needed to be "worked through."

Another Bimmerforums member's reply emphasized the importance of "bleeding the system." This was to prevent what he suspected was (and this is what i think he means) a pocket of air is basically obstructing the free circulation of the radiator's coolant mixture. Thus the car overheats

What is involved with "bleeding the system"? (And he means the raditor system, I suppose.) Another friend added it was important that I have the vehicle level- I had been working in my driveway which does have an appreciable incline.

Lastly, are my worries that there are are probably thermostat problems warranted - yet?
Thanks!!

[02325]

if it has an incline put the frt of the car at the highest point. air will travel to the highest point.

your car will have a bleeder screw on the exp tank. loosen it and fill car with water until water comes out that hole. pour water in slowly. once you get water couming out the bleeder, reinstall screw and crank car with cap off, let it run for 15-20 mins and watch and see if any more air comes out.

it also helps to have the heat set on hot and fan in the middle.

you could also have a sticky t-stat. BMW's are knwon for that.

[choffa]

http://forums.bimmerforums.com/forum....php?t=1709482

[thejlevie]

While it could have been just a bad hose, a broken upper hose nipple on the radiator is a common failure and means that the plastic parts of the cooling system (and all hoses) have reached the end of their life and need to be replaced. Do it now before a complete failure occurs and the engine suffers a serious overheat. A single "trip into the red" can damage the head or head gasket. The cost of the parts is insignificant compared to what it costs to repair the engine if that happens.

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[D. Hitchcock]

thejlevie is some rare combination of BMW master tech and hovering angel.

Praise him and thank him for his assistance.

[thejlevie]

thejlevie is some rare combination of BMW master tech and hovering angel.

Praise him and thank him for his assistance.

You are too generous. I'm not all that good.

[callmedavie02]

While it could have been just a bad hose, a broken upper hose nipple on the radiator is a common failure and means that the plastic parts of the cooling system (and all hoses) have reached the end of their life and need to be replaced. Do it now before a complete failure occurs and the engine suffers a serious overheat. A single "trip into the red" can damage the head or head gasket. The cost of the parts is insignificant compared to what it costs to repair the engine if that happens.

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

*okay* I guess, this pretty much sums up your question. have you checked other radiator parts though? it would be a safe decision to also examine them. call it a safety precaution.

[OUR2004BMW325i]

Our 2004 325i is doing the same thing & sounds like we have had or done the work (and it's been a lot of work trying to establish the true source of the car overheating)with my father in law who is a experienced mechanic (but not one who generally works in foreign cars). Our car still is overheating and we are looking for insight on how to properly bleed the car. Also, if anyone can give us any idea why after replacing the expansion tank, upper hose, bleeder screws twice, thermostat housing, coolant temp. sensor located on/near the head, radiator was replaced 2 yrs ago before we bought the car, our list of replacement parts continues but it's still overheating and appears to still have air in the lines! We have tried bleeding it properly so unless we are missing something on how to do it right, we can think of why it's still overheating. Any ideas on this too?

Sent from my iPhone using BF.com

[linklaterdavid]

Our 2004 325i is doing the same thing & sounds like we have had or done the work (and it's been a lot of work trying to establish the true source of the car overheating)with my father in law who is a experienced mechanic (but not one who generally works in foreign cars). Our car still is overheating and we are looking for insight on how to properly bleed the car. Also, if anyone can give us any idea why after replacing the expansion tank, upper hose, bleeder screws twice, thermostat housing, coolant temp. sensor located on/near the head, radiator was replaced 2 yrs ago before we bought the car, our list of replacement parts continues but it's still overheating and appears to still have air in the lines! We have tried bleeding it properly so unless we are missing something on how to do it right, we can think of why it's still overheating. Any ideas on this too?

Sent from my iPhone using BF.com

I am in the exact same boat as this. I feel like I've tried everything.

[MIKYZZ4]

Have cooling system pressure tested to rule out leaks or headgasket failure.

[linklaterdavid]

I should do a pressure test for sure, but there's definitely no oil in my coolant or visa versa.

[ImTheDevil]

I should do a pressure test for sure, but there's definitely no oil in my coolant or visa versa.

Head gaskets don't only suffer failures in the sections that separate oil channels from coolant galleys. I've replaced a gasket that failed between a coolant galley and a cylinder itself for example. Get the test done, as it can tell you of a problem that inspecting fluids won't show you.

[linklaterdavid]

Head gaskets don't only suffer failures in the sections that separate oil channels from coolant galleys. I've replaced a gasket that failed between a coolant galley and a cylinder itself for example. Get the test done, as it can tell you of a problem that inspecting fluids won't show you.

Will do. Thank you for the response!

[bmwdirtracer]

Well, Hi, David! Fancy meeting you here!!!!

Read and follow thejlevie's instructions above, for bleeding the cooling system. Which of your cars are you referring to? You're doing the bleeding with the heater on? This is crucial.....

Leave the system closed, after filling to the correct level cold, and then driving the car to operating temp. Wait 'til the next morning, then squeeze the top hose. If it is pressurized, or if you find residual pressure when you open the system, you are getting compression into the coolant. I'll detail further tests for you if there remains a question.

Chris

[roninB4]

Would also like to throw this out there. I had a sporadic overheat problem I could not track down. Did the leak down test, bled the air out of the system, replaced the water pump just because. It would idle just fine, even up to 20 minutes with no problems. I'd take it out for a test drive and it would unexpectedly overheat. I had run the garden hose through the radiator and it seemed fine, just couldn't figure it out. What I believe I had was a partially plugged radiator that would pass coolant, just not enough at operating RPM's. A new radiator seems to have cured this, 9 weeks of driving on the Interstate and traffic but the temperature indicator stays in the normal operating range. Verify your other components, especially your head gasket before throwing parts at it, but when nothing else turns up it may be your radiator. This can be especially true in areas that have water with a high mineral content like here. Hope this helped someone.

[linklaterdavid]

Chris, Ronin, Fellas!!

Thank you for for all the truly helpful input. This weekend I plan on bleeding the system again and running the garden hose through the radiator

To run the garden hose water through the radiator would I...?
1) get an attachment for the hose to ensure some greater pressure when spraying
2) remove upper (return) hose at connection to radiator
3) Flush water through the radiator for 5 minutes or so with a decent amount of pressure after disconnecting the lower radiator hose

[bmwdirtracer]

Hi David,
Why are you wanting to put a hose through the rad?

As a "flush". it's not effective..
If you need a "flush", let's consider what you're flushing:
Old coolant? Then drain both the engine block, AND the radiator, and refill with blue BMW coolant and distilled water.
Lime buildup: an acid based coolant flush will help, but the radiator and heater core are probably trashed, if it's lime.
Block sealer? Oh crap, tell me it's not block sealer ("mechanic in a can")

If you really want to do this, flush the radiator BACKWARDS; from lower hose UPWARDS. You are going to be exceptionally wet when you're done, by the way. Keep animals away, coolant is poisonous.



Tell me which car we're talking about. The 540? or the M5?

Chris

[roninB4]

Hi David,
Why are you wanting to put a hose through the rad?
Chris

-Just to be clear on the hose in the radiator comment I made in an earlier post (a few years ago....) I put the hose in the radiator that was OUT of the car to check for flow, suspecting a plugged radiator. I was not advocating nor suggesting anybody do that while your radiator is still installed in the vehicle. As Chris has pointed out it won't be of any use to do this in an attempt to flush the system. My example was a simple test, out of curiosity, that didn't prove anything in the end either. Know what you're doing and why you're doing it before attempting tests, I don't always knew either but it doesn't stop or help me. YMMV

[acoates.e30]

long story short. I blew my headgasket and cracked my head in 3 spots. I replaced the head, gasket, water pump, thermostat, radiator, thermostat housing and rad hoses. Went to bleed my car yesterday and its shoooting coolant out instead of just letting air bubbles out. the heater is blowing cold air and the lower rad hose is stone cold and im able to completely squeeze it, while the top hose is stiff and hot. Does this mean my thermostat is clogged? or is something else happening.

[bmwdirtracer]

Start by telling us what car you're talking about. And, how are you attempting to "bleed" it? Personally, I use a vacuum-fill system, so bleeding is a thing of the past, but there are some excellent how-to's in the FAQ thread at the top of this forum.

[acoates.e30]

Im putting the front of the car up about a foot. removing the cap and bleeder screw. turning the car onto accessory mode and letting that run for bit. Im not getting any bubbles at all through-out that whole part. I then start the car and let it rise to the operating temp. still no bubbles coming from the system as well as no heat in the cabin.

[bmwdirtracer]

I still don't know what car we're talking about, but, assuming it's one of the two you list as your cars, I have to wonder what you're doing with the car in "accessory mode"? Absolutely nothing happens without the engine running. There are various issues you could be dealing with, but it sounds like you've got an air bubble in the system, and your thermostat isn't opening.

Try removing the top radiator hose from the thermostat, and fill the radiator through that hose. After reconnecting it, with the front still in the air, run the engine at about 2000 rpm, cooling system full and closed, heater on, until the temp gauge rises to just over the middle. Then shut the car off, and do not open anything until the engine is fully cooled again. Then fill the expansion tank to the correct level, close it up, and run the engine again until just past midway, or, if everything has gone well, when you get good heat and the temp stops rising.

Don't let the gauge go over 3/4 ! Let us know if this fixes the issue. It usually does, but really, the best way to fix this issue is to vacuum-fill the system.