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Discussion Starter · #1 · (Edited)
Can driving 4miles with an expansion tank separated at "weld" seam damage the engine?

Hi folks,

Recently I was sitting at a red light I heard a popping sound, right after the light turned green I pulled over and saw some dripping of what looked like coolant close to the passenger-side front wheel well. I drive a 2005 M3 SMG.

I checked the engine temp gauge it had moved slightly to the right of mid-point. (it normally sits at exactly mid-point). I decided to drive the car straight to my repair shop which was about 4 miles away. I was watching the temp gauge the whole time, and as I started moving the temp went almost perfectly back to the normal (mid-point). During the drive the low coolant light also came on.

When I got to the repair shop I popped the hood and noticed the top of the expansion tank had popped, and I could still see coolant below the float.

I got the car back after replacing the coolant tank, it runs beautifully and the temp gauge runs exactly at mid-point when it's running. At the repair shop I was told that engine had recorded the fault code "Engine Temp Implausible" several times. And the cooling system and engine may have suffered damage, but they found no evidence of it or any other fault codes.

So I am quite worried that maybe the engine heated more than the temp gauge was show during the 4 mile drive to the repair shop. And I have two questions, that may (or may not) help me worry less.

1) When the expansion tank pops at the seam, does that cause all the coolant to leave the cooling system? I know the M3 cooling system runs at high PSI, but I thought it was the excess coolant that this tank stores.

2) Does the engine temp gauge use a sensor that is independent of the coolant temp? If the coolant level had gotten really low is the engine temp gauge still reliable? I worry that may be engine was overheating and it was not showing the right temp.

Now I am starting to think I should have had the car towed for the 4 miles, but I thought I was being responsible by watching the temp gauge.

Would appreciate feedback from someone who really knows how an 2005 E46 M3 cooling system works.

Thanks.
 

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Not an expert, but same thing happened to my car and it runs flawlessly now after everything has been fixed. My guess is you are fine and that the temp gauge is reliable enough during such an event. Been a while since I've flushed the system with new coolant, but if I remember correctly it holds 4 gallons approximately and I believe about a gallon and a half had escaped. After such a short distance you should be fine. Oh and just because I am curious, is your car by any chance low mileage and/or not driven frequently and under what conditions do you regularly park?
 

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Discussion Starter · #4 ·
Not an expert, but same thing happened to my car and it runs flawlessly now after everything has been fixed. My guess is you are fine and that the temp gauge is reliable enough during such an event. Been a while since I've flushed the system with new coolant, but if I remember correctly it holds 4 gallons approximately and I believe about a gallon and a half had escaped. After such a short distance you should be fine. Oh and just because I am curious, is your car by any chance low mileage and/or not driven frequently and under what conditions do you regularly park?
Thanks for sharing. Did you drive at all after it happened? How many miles? How long ago was it?

I drive my car every day and everywhere, love the car. It does have low miles approx 59K, and it is always parked either in my garage, or in a covered parking spot at work. I live in AZ where it gets pretty hot, it was about 104F on the day this happened.

I have read in some places that the entire cooling system holds only 2 gallons, but 4 gallons sounds more plausible considering how engine there is.
 

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i think you should be fine. don't worry.

how hot does arizona get ? here in California is around 68 degrees. I'm moving to Arizona next month and I'm a bit worried that i might not be able to tolerate the heat :eek: lol
 

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Discussion Starter · #7 ·
i think you should be fine. don't worry.

how hot does arizona get ? here in California is around 68 degrees. I'm moving to Arizona next month and I'm a bit worried that i might not be able to tolerate the heat :eek: lol
Thanks, I hope so. It in the 100s these days, it will go to like 115F even 120F in the peak of summer. But it's not as bad as it sounds.
 

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Thanks for sharing. Did you drive at all after it happened? How many miles? How long ago was it?

I drive my car every day and everywhere, love the car. It does have low miles approx 59K, and it is always parked either in my garage, or in a covered parking spot at work. I live in AZ where it gets pretty hot, it was about 104F on the day this happened.

I have read in some places that the entire cooling system holds only 2 gallons, but 4 gallons sounds more plausible considering how engine there is.
To sum things up.. My car is an 04 model and has just over 45k on it. Unfortunately I can't tell you the exact conditions because I bought my car on auction. That was just one of the things that needed to be fixed on it. Like I said I wouldn't worry about it, my car is mechanically sound and runs great.

I asked you those questions earlier because I thought this issue may have been environment or use related. I guess it's just a fault from the factory, who knows maybe not enough sealant was applied.

The entire cooling system holds approximately 4 gallons some people just don't drain the block which contains most of the fluid. There was no more than a pint of coolant left in my car afterwards.
 

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Discussion Starter · #12 ·
To sum things up.. My car is an 04 model and has just over 45k on it. Unfortunately I can't tell you the exact conditions because I bought my car on auction. That was just one of the things that needed to be fixed on it. Like I said I wouldn't worry about it, my car is mechanically sound and runs great.

I asked you those questions earlier because I thought this issue may have been environment or use related. I guess it's just a fault from the factory, who knows maybe not enough sealant was applied.

The entire cooling system holds approximately 4 gallons some people just don't drain the block which contains most of the fluid. There was no more than a pint of coolant left in my car afterwards.
Thanks, I see. From my slightly obsessive reading up, I found that the coolant tank popping at that seam is quite common and seems to be age/fatigue related.

When you said "There was no more than a pint of coolant left in my car afterwards" did you mean after draining all the coolant from the system including the block?
 

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Isn't the overflow tank typically the highest part of the cooling system? If that's the case, I don't think it'd be possible to loose all of your coolant due to a tank failure.

It sounds like your oil temp didn't get into the red, so I'd think you'll be fine.

I'm not sure where the water temp sensor is on these cars, but it's not uncommon for them to stop working if you lose to much coolant. No water hitting the water temp sensor = nothing to measure......
 

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Our expansion tank isn't an overflow tank and isolated from the system. It's part of a sealed system. But, I think you should be fine if you get your issue fixed.

The level sensor is recorded by a magnet on the bottom of the ET float. The temp sensor is on the lower radiator hose...at least on non-M it is. Check realoem.

Anyway, you didn't loose all your coolant, and the air entering the system from that crack would likely just stay there and not get sucked into the system.

Anyway...sound like you'll be fine and I wouldn't worry about any severe damage.

HTH
 

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Discussion Starter · #16 ·
McGary911 and dMax, thanks for the feedback. McGary911 it's funny you mention the oil temp, I usually do scan it while driving, but in this instance as far as I recall I was focused on the coolant temp gauge. But I am quite certain that the oil temp was completely at the normal point. Also I figured, as you point out, that being the highest point helps from coolant loss due to gravity, but I also knew that this is a closed pressurized system as dMax pointed out. I have heard that the "Engine Temp Implausible" fault gets recorded when the temp sensors reported value is inconsistent with the values reported by other sensors. In this case, may be one temp sensor was reporting a much cooler temp than expected by the ECU. I heard there is more than one temp sensor (guessing others may not be coolant related).

dMax, it makes sense for the coolant temp sensor to be located lower in the system. And yes, I got it it fixed right away, and the car runs just beautifully as always.

So taking all the feedback into account, the fact that the engine temp only when went slightly over mid-point, and then returned to mid-point when the car was moving, and that it still runs very nicely (after the new expansion tank), I think I will stop worrying :)
 

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Just worry a little bit. If all they did was replace ET, and it was original, that might honestly be all it was. But, make sure you test it by idling somewhere...where if need be, you could start to move and cool things down.

If your fan wasn't working, or therm stuck closed, you'd notice an issue at idle...and if you get hotter, coolant will expand more, and if the ET had been overfilled, that might be enough to pop an old ET. But, they often break there, so don't let me panic you too much.

If you notice anything else, I'd suggest you go a little further in your repair...as in, if therm, do WP also. Check pulleys and belts, drain from engine block. The M cooling system is pricey, I know! OE is over $1000, but I think I've seen basic kits for maybe $650...something like that...not sure of the parts' quality though.

Anyway, I like low hanging fruit...if you're in somewhere anyway, check out realoem.com for what else is nearby.
 

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Discussion Starter · #18 ·
Just worry a little bit. If all they did was replace ET, and it was original, that might honestly be all it was. But, make sure you test it by idling somewhere...where if need be, you could start to move and cool things down.

If your fan wasn't working, or therm stuck closed, you'd notice an issue at idle...and if you get hotter, coolant will expand more, and if the ET had been overfilled, that might be enough to pop an old ET. But, they often break there, so don't let me panic you too much.

If you notice anything else, I'd suggest you go a little further in your repair...as in, if therm, do WP also. Check pulleys and belts, drain from engine block. The M cooling system is pricey, I know! OE is over $1000, but I think I've seen basic kits for maybe $650...something like that...not sure of the parts' quality though.

Anyway, I like low hanging fruit...if you're in somewhere anyway, check out realoem.com for what else is nearby.
Haha, "worry a little bit"...always I guess. The thermostat and bleeder screw were also replaced, will pay attention to the fan, when I drove yesterday idle temp was at mid-point will check if fan turns on, next time.

I actually checked if the expansion tank was overfilled, the float "stick" was about 1/4 inch above the top of the neck of the tank with the engine cold, so I guess it is slightly overfilled, since it's supposed to be flush with the top of the neck.

Since I would like to keep the car, I was thinking I may do a full cooling system overhaul, radiator, pulleys, water pump, and all, in about a year as preventative maintenance.

The very positive part of this whole experience is how much learnt about the E46 cooling system, for example that water pump impellers are made of plastic (!) and they can break off and lodge in the cooling system. Beats me why BMW would not make the impeller out of a corrosion resistant alloy such as stainless steel (maybe weight concerns, but more likely cost).
 

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Make sure you're reading the guide for the cooling dipstick right. On my non-M, 1/4" above the filler neck is full. But be careful as there isn't an overfull mark. Best to be between min and max levels.
 

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Thanks, I see. From my slightly obsessive reading up, I found that the coolant tank popping at that seam is quite common and seems to be age/fatigue related.

When you said "There was no more than a pint of coolant left in my car afterwards" did you mean after draining all the coolant from the system including the block?
Basically all the fluid that was left was just what was in parts of the system where you would need it under pressure in order to get it out. I drained that sucker good lol, it was a lot of fluid.
 
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