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Old 01-04-2013, 08:30 AM   #1
petemo94
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Cold Lower Radiator Hose - WTH?

E46'ers

Just swapped out the entire cooling system components (except for radiator).

EVERYTHING is working as expected. Heat in car, thermostat dead-center, no air in lines (as far as I can tell), no leaks,... Got the parts from ECS Tuning.

After a 25 minute drive with about 6-7 miles on the highway, I checked for leaks - none.

However I also check the lower radiator hose and noticed it was ICE cold! Granted the temperature was 31-degrees.

Couldnt find a sufficient explanation hence my questions:
  • With all symptoms pointing to being OK - why is that lower hose so cold?
  • Is the radiator THAT efficient to cool things off so fast?
  • The thermostat housing is warm though. I don't suspect it being stuck open bc the temp-gauge is right on and the heat is HOT!
  • Can the fact that the heat is on and the heater core being engaged, drive that much heat away from the radiator's lower hose?
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Old 01-04-2013, 08:38 AM   #2
Rotha
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maybe your radiator is clogged, how do you know you have no air in the lines?
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Old 01-04-2013, 08:47 AM   #3
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maybe your radiator is clogged, how do you know you have no air in the lines?
No symptoms of it being clogged. Yesterday, I went on a longer ride, more highway and finally noticed the lower hose was "warm" but certainly not hot like the upper hose. Today, I tried to duplicate the same path, but had to shorten it. This time the hose was cold.

When I drained the coolant and saw the internals of the water-pump hole, the water-paths were crystal clear. Not a sign of any issue. I suspect the radiator is the same too (here's hoping).

But my question really is, should the bottom hose be warm? what is the normal time/mileage that it becomes warm to touch? Just curious if anyone knows.
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Old 01-04-2013, 08:59 AM   #4
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if your coolant is flowing and the radiator is doing its job, the hose should be cool. if the top is hot and bottom cool job done.

especialy if ouside temps are low. thermostats job to limit flow to maintain engine temps.
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Old 01-04-2013, 09:47 AM   #5
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it took you 25 minutes to go 6 miles? Hmm i would probably go on a longer drive. that hose should not be cold to the touch. i would definitely bleed again. did you make sure you turned on the heater when bleeding? make sure the front of the car is at least level or HIGHER during the bleed process. follow it to the T in my cooling thread
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Old 01-04-2013, 09:57 AM   #6
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it took you 25 minutes to go 6 miles? Hmm i would probably go on a longer drive. that hose should not be cold to the touch. i would definitely bleed again. did you make sure you turned on the heater when bleeding? make sure the front of the car is at least level or HIGHER during the bleed process. follow it to the T in my cooling thread
Will do this again this weekend. Had to get a new upper hose from ECS tuning because the one they sent me was defective (o-ring inside was flat from a 7-11 o'clock position - causing a leak). Will replace with new hose coming today.

I travelled probably 15 miles, of which 6 were on the HWY.

Was surprised at the end of this trip that the bottom hose was COOL. Yesterday, with almost a similar drive, the bottom hose was luke warm, but temps today were 31 (.vs. 50 yesterday).

I'm hoping the radiator is that efficient though and that I'm worrying about nothing.
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Old 01-04-2013, 10:09 AM   #7
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When you bled, how long did you observe bubble-free water emerge from the expansion tank bleed hole?
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Old 01-04-2013, 10:36 AM   #8
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you should bleed for air again but just to let you know....

the lower radiator hoses pump cold fluid from the radiator back into the engine. therefore, it is always going to be colder. if you have a scanner, try reading the temperature of your engine, coolant temp, etc.

I hope this helps. good luck

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Old 01-04-2013, 10:40 AM   #9
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you should bleed for air again but just to let you know....

the lower radiator hoses pump cold fluid from the radiator back into the engine. therefore, it is always going to be colder. if you have a scanner, try reading the temperature of your engine, coolant temp, etc.

I hope this helps. good luck
+1

Why the name change?
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Old 01-04-2013, 10:47 AM   #10
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+1

Why the name change?
my PR manager told me I have to do something to change my image for 2013. I figure I would change my name to give me a clean start but I don't want to elaborate on this further because I am afraid this thread will get hijacked and derailed by a certain group of people.

OP....I hope you update us on this problem.

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Old 01-04-2013, 11:10 AM   #11
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lol i guess i like it.
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Old 01-04-2013, 11:53 AM   #12
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Originally Posted by flashmeow View Post
you should bleed for air again but just to let you know....

the lower radiator hoses pump cold fluid from the radiator back into the engine. therefore, it is always going to be colder. if you have a scanner, try reading the temperature of your engine, coolant temp, etc.

I hope this helps. good luck
Great idea but I don't have access to a scanner. Will bleed again this weekend.

IF there was air in the lines HOW long will it take to bleed the air out with temp set to 91? 2 mins? 20 mins?

Also agree that the lower hose will be cooler. But I wasn't expecting it to be "cold". But back to my OP, could the radiator be that efficient? Could air flow at 31 degrees be that efficient in cooling? Those are the questions.
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Old 01-04-2013, 11:54 AM   #13
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Great idea but I don't have access to a scanner. Will bleed again this weekend.

IF there was air in the lines HOW long will it take to bleed the air out with temp set to 91? 2 mins? 20 mins?

Also agree that the lower hose will be cooler. But I wasn't expecting it to be "cold". But back to my OP, could the radiator be that efficient? Could air flow at 31 degrees be that efficient in cooling? Those are the questions.
You should bleed for at least two to three minutes. Not complicated at all! GL!!!
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Old 01-04-2013, 10:31 PM   #14
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I drove my car today in a similar fashion to what OP described, and the return hose was cool to the touch in 35F weather. It was a bit warmer than the surrounding air, but not by much, my cooling system has not been opened in about 3-4 months since I replaced it, and it was properly bled. not to mention that any air bubbles should have worked their way out by now. I'd wager that what the OP described, at least in cold weather, is functioning as intended.
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Old 01-04-2013, 10:49 PM   #15
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I drove my car today in a similar fashion to what OP described, and the return hose was cool to the touch in 35F weather. It was a bit warmer than the surrounding air, but not by much, my cooling system has not been opened in about 3-4 months since I replaced it, and it was properly bled. not to mention that any air bubbles should have worked their way out by now. I'd wager that what the OP described, at least in cold weather, is functioning as intended.
You are correct my friend, at least as compared to my current system.

Here's what I found:
  • Ambient air temperatture DOES matter. Obviously the colder out, the better chance the lower hose is colder. No surprise there.
  • I've bled my system correctly the 3 previous times I've worked on the car. Each time yielding the same results: heat in cabin, proper levels in ET when it cooled, temp-gauge in the middle (note - all cooling components replaced including clips, sensors, hoses, WP,...)
  • However the BIGGEST factor (I believe) is whether the heater core is engaged. I drove for 15 minutes with heat ON. Result: COLD hose; after 15 minutes of more driving this time with NO heat, lower hose is HOT.

So based I what I found, outside temps and heater being used or not, appear to have a factor on whether the lower hose is cold, warm or hot.

Will try again tomorrow (with and without heater on) and see if this stands true.

Would like to hear if others report the same (esp with temps <35 & heat on high) to see if lower hose is cold.

Thx for the help in this. Think the issue is resolved (for 60K miles).
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Old 01-05-2013, 06:21 PM   #16
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Okay, here's a story that may confirm your beliefs, though from a different vehicle (and era) entirely. In the late 60's, I was driving with my mom in our GTO through a heavy snow near Lake Tahoe. The temperature idiot light came on, so we immediately pulled into a gas station. Turned out the car was overheating because there was a blockage in the bottom of the radiator, preventing most of the water (not coolant) from returning to the engine. The blockage? Ice! The water had gotten so cold at the bottom of the radiator that it was freezing solid, or perhaps had not melted enough after spending the day in the ski area parking lot. So yes, it's quite possible that your coolant is getting cool or cold before returning to the engine. At least it was in our car.
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Old 01-05-2013, 07:40 PM   #17
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Originally Posted by sgoetz628 View Post
Okay, here's a story that may confirm your beliefs, though from a different vehicle (and era) entirely. In the late 60's, I was driving with my mom in our GTO through a heavy snow near Lake Tahoe. The temperature idiot light came on, so we immediately pulled into a gas station. Turned out the car was overheating because there was a blockage in the bottom of the radiator, preventing most of the water (not coolant) from returning to the engine. The blockage? Ice! The water had gotten so cold at the bottom of the radiator that it was freezing solid, or perhaps had not melted enough after spending the day in the ski area parking lot. So yes, it's quite possible that your coolant is getting cool or cold before returning to the engine. At least it was in our car.
Make sense, in terms of what I've seen over the past 3 days (30 degrees outside) - lower hose is cold due to a number of factors.

But one thing I've noticed is IF its cold out (< 30 degrees), you are using your heater core, the lower hose will be cold to touch. The heater core acts as a source that pulls heat AWAY from the radiator. When I turn off the heat, more coolant appears to go thru the radiator and it tends to heat up the bottom hose.

Issue is solved/understood. Enjoying the fact that the cooling system is as efficient as it is with new hoses, coolant,...

Thx for the help on this.
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Old 02-02-2013, 06:49 PM   #18
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I drove my car today in a similar fashion to what OP described, and the return hose was cool to the touch in 35F weather. It was a bit warmer than the surrounding air, but not by much, my cooling system has not been opened in about 3-4 months since I replaced it, and it was properly bled. not to mention that any air bubbles should have worked their way out by now. I'd wager that what the OP described, at least in cold weather, is functioning as intended.
So here's a further update on trying to understand this German cooling system.
  • Temperature outside was 43 degrees, car was already hot from using it for last hour.
  • Went on a 20 minute country ride. Was going 45-55 MPH the whole time
  • Pulled over to go to shopping center - LOWER Hose was cold
  • Drove home from shopping center 1.5 miles - LOWER Hose cold
  • Let the car idle in front of the garage so I could pick up my ramps from putting on my under-carraige - Heard the fan kick on while idling. Spent about 3-4 minutes idling.
  • Pulled car in, opened hood, LOWER hose was HOT!
  • Yes, the car has been properly bled. Has been over 1 month since I opened ET cap. No issues with leaks or temp-issues.

So I've come to the conclusion that the cooling system and radiator is quite efficient while the car is in motion and air is coming over the radiator. Water pump (Geba) is new along with every other part of the cooling system. With the lack air over the radiator, it causes the whole cooling system to heat up.

I've still got the ET I took out. Next step is to open this up and take photos and share.
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Old 02-03-2013, 07:36 AM   #19
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Here is an hour long drive in my 330Ci in about 20 degree weather. The Coolant temps are graphed, notice how the radiator outlet temp starts at about 50 F (in my garage) cools down to around 20ish and stays below 60 F until I come to a stop. My heat would have been set to Auto with an inside temp setting of 68-72F.

At about the 200 mark on the X axis you can see when the thermostat first opens the outlet temp actually goes down as the coolant comes out of the radiator cooled down to ambient temp.

At the right hand end you can see the outlet temp raise to about 150 F and then cool down to about 100 F even though I didn't above about 30 MPH.

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Old 02-03-2013, 09:16 AM   #20
petemo94
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Here is an hour long drive in my 330Ci in about 20 degree weather. The Coolant temps are graphed, notice how the radiator outlet temp starts at about 50 F (in my garage) cools down to around 20ish and stays below 60 F until I come to a stop. My heat would have been set to Auto with an inside temp setting of 68-72F.

At about the 200 mark on the X axis you can see when the thermostat first opens the outlet temp actually goes down as the coolant comes out of the radiator cooled down to ambient temp.

At the right hand end you can see the outlet temp raise to about 150 F and then cool down to about 100 F even though I didn't above about 30 MPH.

Well that explains my observations perfectly. Thx for this!

What kind of SW did u use to get this? I'm only 2 months into
My bmw ownership and would love to play with this SW package.

Thx again.
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