Let's Play A Little Game Called "Guess Which Cooling System Component Failed"

[kayger12]

Howdy boys and girls! Let's see who gets the winning guess.

Relevant Info: 75K miles. Thermostat and water pump changed at 57,500. Expansion tank, hoses, and coolant temp sensor changed 3 weeks ago. All parts are OEM. Radiator is original.

Upon completing the recent job she was filled with fresh coolant and bled. Drove her on a 200 mile round trip with no issues.

Checked coolant level after that trip and needed to add about 2 ounces of coolant. I assumed that was due to an air bubble or the fluid settling out after the initial fill.

Drove her on and off on shorter trips (< 30 minutes) for the next few weeks.

Fast forward to today:

Left for a funeral up in north Jersey (about 200 miles round trip). About 15 minutes into my drive and cruising comfortably north at highway speed I see the low coolant light come on. Temp needle was dead center.

Fortunately I was right at an exit. I sliced to the exit and jumped right off into a parking lot and shut her down. Temp needle never moved off 12 oclock.

Opened up the expansion tank and found her bone dry. A quick visual (looking down from the top of the motor) showed some coolant pooling on the top of the lower splash shield.

Called the wife and had her check the garage floor. Sure enough, evidence of coolant leakage.

I grabbed my trusty emergency coolant supply that I keep in the trunk and poured it in.

I then began the 20 minute drive home (surface streets this time, no highway) with my eyes glued to the cluster.

She made it home with no further indicator lights. Temp needle remained at 12 oclock.

I parked her in the garage, hopped in the Mazda, and set about my day.

I won't be able to get at the engine bay until Friday. I have my own suspicion of the cause but I figured we could all take a shot at blindly diagnosing before I get in there.

Thoughts?

[midlandtech]

My guess is loose hose or sensor at the bottom hose of the radiator

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[danewilson77]

Exp tank. I'll bet the odds, even though you said it's been replaced.

I do like the theory of a hose not being properly set or one without an o-ring as well.

[johnrando]

Bummer! Man, I'd hate for it to be the tank since it's new, but it sounds like it. But, given that it is new, my guess is loose/cracked hose.

[az3579]

Asking for a clue; is the top of the bay dry? As in, is the only site of wetness at the bottom where the splash shield is?

I'm putting my money on cracked plastic on the bottom of the radiator fitting for the hose.

[kayger12]

Top of the bay appeared dry.

I like where everyone's heads are at so far.

All things I've been thinking.

Looking forward to getting in there Friday and seeing what's going on.

[zhpnsnv]

Aw crap. Glad you didn't do any damage.

[Scorpius]

It will be the one thing You didn't replace the radiator

[Avetiso]

My last leak was lower house returning to the tank. Replaced the o ring and that was that.

Sent from a junkyard via GS4.

[kayger12]

Aw crap. Glad you didn't do any damage.

Yeah, I was watching that coolant temp gauge like I was squared off with Ike Clanton at the OK Corral.


My last leak was lower house returning to the tank. Replaced the o ring and that was that.

Sent from a junkyard via GS4.

It would be awesome if it was something that easy.

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[az3579]

It will be the one thing You didn't replace the radiator

Hey, you never know; it could be a part already swapped.
My upper radiator hose started leaking less than a year after I replaced it...

[LivesNearCostco]

For the guessing contest, I answer it's the base plate on which the ET sits, or the or drain plug in the base plate. Maybe you didn't seat the tank fully on it, or the locking clip was locked while you seated it. (Or not locked after you seated it.)

None of the usual suspects seem to make sense at 75K after hoses, ET, thermostat and temp sensor were replaced. But here's a list of possibilities.

More likely

Radiator cracked, but usually doesn't happen until >100K miles
Lower hose not fully seated on radiator
Temp sensor worked lose out of lower hose


Less likely

Bleeder screw loose or over-tightened and cracked (you'd see dried coolant on upper hose)
ET cap loose (but then you'd see dried coolant on top of ET)
Base plate cracked, or ET not fully seated on base plate
AT cooler, but you don't have one
New ET, hoses, or thermostat failed
Heater core failed (but then it would leak inside the cabin, right?)
Small hoses to ET failed or not properly locked onto new ET (I think one to heater core, other to engine)
O-ring inside bottom part of ET where it mounts on base plate is out of place

[JupiterBMW]

I then began the 20 minute drive home (surface streets this time, no highway) with my eyes glued to the cluster.

Just for future reference, you're typically better off driving the highway as the car will actually run a little cooler. While the engine is under a constant load, the continual air flow over the front end will help keep the temperature in check. Having a 6 speed allows us to cruise at a fairly low RPM, and you can always just run slower in the right lane (60-65mph). Its fast enough to keep up and keep that airflow, yet slow enough to keep the revs quite low.

Also, turning the heat on (NOT the defrost, any setting that does NOT use defrost) and then opening the windows a bit is the way to roll. That will ensure maximum heat extraction out of the cooling system, while still keeping you comfortable. And being on the highway ensures maximum cooling airflow over the radiator. Also, your trip home will be faster, therefore less time driving.

Good luck with the repair. :thumbsup My experience in troubleshooting is that it is typically the last thing you messed with, whether its a bad part, or a loose/improperly seated fitting. But, Murphy's Law will state that it is the ONE thing you didn't swap. :facepalm

[kayger12]

For the guessing contest, I answer it's the base plate on which the ET sits, or the or drain plug in the base plate. Maybe you didn't seat the tank fully on it, or the locking clip was locked while you seated it. (Or not locked after you seated it.)


These were my initial suspects (base plate or drain plug).

Appreciate the excellent list of other possibilities.

Joop- good info, man.

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[ELCID86]

...turning the heat on...
Yep.

Anyone think it odd that the temp needle didn't move--at all?

[JupiterBMW]

I read quite a bit back a few months ago that the needle won't move unless the temp gets outside a range. From what I understand, the gauge is just there as a placebo effect of sorts. It will stay in the middle as long as the temp is in a normal 'range'. If it goes outside this range, the temp needle will then move up or down to a predetermined location, based on the new temp, again, another range slightly higher or lower. And if it continues to go hot to the danger zone, the needle will move again, into the red area.

I could be wrong, but I swore I read that somewhere...

[Hermes]

^ You are correct. There is a zone that will register as straight up on the dial, it's an 80's era design to keep people from running to the dealer for service because they thought something was wrong with their car. My E21 fluctuates quite a bit during normal driving, freaked me out at first until I realized that the gauge is accurate and not like the E46 version

[kayger12]

Yep, stayed within range.

The only thing that made me hesitate using the heat was that I had limited coolant and was afraid that if the heater core had drained, turning the heat on would have opened the valve and pulled some of my limited coolant to the heater core.

I could be completely wrong there, but that was my train of thought.

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[JupiterBMW]

Yeah, that is possible Keith... Either way, not to worry now as she's home without overheating... Next step, get'er opened up and find out what the issue is!

[alexandre]

The needle stays dead center between~80-112 degrees celcius. Red starts at around 128. I monitored it with the hidden OBC when I was having issues with air in the system.

[ELCID86]

^^ you guys are such nerds... I love it! Thanks for the info.

[Hornung418]

Guessing radiator. Its an fun and easy job.

GS3 + TT4

[kayger12]

Have to take the new Mazda up for an oil/change service this morning. After that is oil change for the old Mazda.

Figuring by mid-afternoon I'll start digging into the ZHP.

[JupiterBMW]

Looking forward to finding out who was right in their guesses.... And what was the prize for this contest again? I must've missed that in the original post. :biggrin

[kayger12]

Survey says.............


Leaking from the connections at the bottom of the expansion tank.

No leak when not running. Wasn't leaking at idle and normal operating temp. Ran her up to 3k rpms for about 20 seconds and jumped back underneath to see this:

http://youtu.be/Abe-T_VW8lM

I know it looks like it's coming from the drain plug, but it isn't. It's coming from the smaller of the two openings at the bottom of the tank.

Not seated properly I'm assuming?

I also realized that I never replaced the sliding lock clip at the bottom of the tank. It was still on the old tank. Switched that over right after I stopped the video.

If I push up on the expansion tank from underneath or wiggle it side to side, I can induce much heavier leaking.

Solutions? Can I just press down from the top and lock it in, or do I need to pull everything apart?

Thoughts?

[danewilson77]

Yep. Makes sense. Good going KG.

Sent from my Samsung Galaxy S4

[LivesNearCostco]

Can't see video on YouTube as it's marked private. If it didn't leak when you first installed the ET, probably it was properly seated but when hot the pressures pushed it up a bit because the locking clip wasn't installed. At least that's my theory. My suggestion would be to let it cool, open clip, push down on tank from above to make sure it's seated, then lock clip in place. (If tank is not seated and clip is in locked position, it might prevent you from seating tank fully.) Run car up to temp and see if it still leaks. If yes, you have to pull the tank to see if the platform is cracked or O-ring is out of place.

[kayger12]

Checking in. Sorry about the video. Just changed the setting.

I decided I had nothing but time and an empty house, so I ripped it back down and disassembled the exp tank/frame.

It was on there pretty good. I don't see any cracks and the o-rings look good.

Just reassembled her and am getting ready to add the coolant back in.

I'll check back in in a few.

[brettbimmer]

Hope that was it. Good luck burping baby Bimmer.

[kayger12]

^ :)

Looks like she's all fixed, gents.

After comparing the video to the tank after I disassembled/reassembled, it appears that the smaller of the two plastic tubes at the bottom of the tank was not fully seated.

In my fear of being too rough on the plastic I induced an ID 10 T error.

Thanks for all of the help and ideas. Greatly appreciated as always.

[ELCID86]

glad nothin was broke.

[kayger12]

glad nothin was broke.

Amen. Me too. Pictured myself chasing gremlins and making trips to the dealership parts counter...

[Hornung418]

ID 10 T made me chuckle. Glad it was nothing major.

GS3 + TT4

[kayger12]

ID 10 T made me chuckle. Glad it was nothing major.

GS3 + TT4

Thanks, bud. Anytime I do something coolant related I think of you and the Horney plug. :)

[Hornung418]

How can we forget...

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[kayger12]

For the guessing contest, I answer it's the base plate on which the ET sits, or the or drain plug in the base plate. Maybe you didn't seat the tank fully on it, or the locking clip was locked while you seated it. (Or not locked after you seated it.)



This, by the way, was the spot-on winner. Kudos!

[JupiterBMW]

Nicely done, KG. Glad it was minor...

[zhpnsnv]

Glad it's sorted!

[kayger12]

Nicely done, KG. Glad it was minor...


Glad it's sorted!

Thanks, gents.

[az3579]

Darn, I thought I had this one. Oh well!
Grats on finding the problem. Order is restored.

[johnrando]

A little late but glad that worked out Keith. (Guess you could say you had to do a "remix"). :)

[LivesNearCostco]

Reviewing my guess, it was really 3 guesses in one. Kind of cheating!


This, by the way, was the spot-on winner. Kudos!

[kayger12]

A little late but glad that worked out Keith. (Guess you could say you had to do a "remix"). :)

Hehe. I love anyone who can get a veiled Rush reference in a cooling system thread.

Well played!


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[BCS_ZHP]

Glad you didn't let some "Universal Juveniles" "Carress of (your) Steel" and do a "Fly By Night" repair. That surely (don't call me Shirley) would have brought your cooling system to the "Limelight", it would have been a "Countdown" to see if there was "Grace Under Pressure" as it rose to operating temperature. We here in the Mafia would "Hold Your Fire" with a "Show of Hands" to see if your "Power Windows" operated correctly after this repair. Looks like all "Signals" are go, count this as "One Little Victory" for the DIY'er, its sure a "Far Cry" from having to pay the stealership.

[kayger12]

Glad you didn't let some "Universal Juveniles" "Carress of (your) Steel" and do a "Fly By Night" repair. That surely (don't call me Shirley) would have brought your cooling system to the "Limelight", it would have been a "Countdown" to see if there was "Grace Under Pressure" as it rose to operating temperature. We here in the Mafia would "Hold Your Fire" with a "Show of Hands" to see if your "Power Windows" operated correctly after this repair. Looks like all "Signals" are go, count this as "One Little Victory" for the DIY'er, its sure a "Far Cry" from having to pay the stealership.

Best. Post. Ever.

Love it!

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[Hornung418]

Damn Bruce...that's an amazing post.

GS3 + TT4

[BCS_ZHP]

Credit Scott Rodney Stiger, dormmate my freshman year, Rush junkie to the extreme. Sometimes Rush-isms pop out of my brain housing group and I'm not even sure how or why, then my memory connects them back to Rush, yes, please credit the Scott Rod.

And I suspect behind his thin veil as Mafia moderator, Keith is cut from the exact same mold :rockon:rockon

[johnrando]

LOL, love it Bruce! I've seen Rush in concert 28 times.