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Discussion Starter · #1 ·
Hi everyone.

I'm after some advice on what to do with my car.

Background is that it overheats on the gauge up to the 3/4 dot, or on the "hidden" dash functions up to 100-103 degrees. BUT it only does this on hot days 35+ degrees in Sydney Australia. So in Winter it's fine, if it's 25 degrees its fine.
I know the needle sits in the middle between 85 and 95 degrees.

The other thing is, I know the user manual says anywhere between cold and hot is "normal", but I've owned the car for 6 years (and summers) and it's only been happening the last 3 years (summers).

Here is the list of things that have been replaced. In no particular order

Radiator x2
Fan clutch x3
Thermostat x2
Water pump
expansion tank
Bottom radiator hose temp sensor
Engine block temp sensor

I even swapped the ECU and instrument cluster to see if they were sending/receiving the wrong info.


Here is a timeline of receipts I have. Or photos I've taken of the temps to keep for my info.

Date Task

28 Oct 2015 Fan clutch replaced
1 Dec 2015 Replace thermostat - Inspect water pump
20 Jan 2016 First overheating photo
22 Jan 2016 Replaced suspect block radiator
25 Feb 2016 47 degree day - NO OVERHEATING - Photo. Oil just above 100
23 Jul 2016 Oil temp sensor replaced (ebay). Had not worked for maybe 8weeks.
1 Nov 2016 Detent spring replaced
6 Nov 2016 1.5 degrees outside, oil 90, water middle
24 Nov 2016 Evolve Tune / CSL SMG / M Track mode
5 Dec 2016 Split expansion tank - Replaced
20 Dec 2016 Head gasket, water pump, vanos.
29 Dec 2016 42 degrees, overheated 100 degrees. Photo
14 Jan 2017 41 degrees, overheating 97 degrees. Photo
21 Jan 2017 Gunk in expansion tank. Photo
27 Jan 2017 Check overheating - 5 Degrees difference in water temp at radiator (inlet to outlet)
31 Jan 2017 Remove and inspect radiator - New thermo and water pump o-rings
1 Feb 2017 Replace Radiator


Any help or info would be appreciated.
 

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Discussion Starter · #3 · (Edited)
Well, it's never actually "overheated" like to the red zone, it only ever goes to the 3/4 dot.
Sorry, the circumstances differ, but it usually happens when driving down the motorway, doing 80-110, in 6th gear. The needle will start to climb, and sit there for a bit, maybe a couple of minutes, then come back down. OR if I pull over, it drops almost instantly. The other thing is, its most noticeable going up hill, the temp will climb going up a large hill, still doing highway speeds, and then when you reach the top and go down the other side, it will drop again, almost instantly. It never overheats at idle.

But then sometimes, it can be a 4 minute drive home from the shops and it will get warm. Like today up to 97, stayed there for 30 seconds, and then slowly came back to 93.

The electric fan has not been changed, however, it seems to be working 100%, that is as far as I know. I had a read of the link and there's some good info, but here's what I have done to "test" it. ( I will do the test from the link you posted ) But I got some water in a container, with a spare CTS attached, and put it in the water, I added hot water to the container so the temp rose slowly. When the water temp got to 90degrees (I had a digital thermometer in the water) the fan was running at it's full speed. Obvious by how loud it was. As soon as the temp dropped back down to 89degrees, the fan slowed down. My issue with this is, that if the water coming out of the radiator is 89 and the fan is not pushing as much air as possible through the radiator, how is going to cool enough to keep the block temp below 96 (the temp at which the needle moves towards the hot side).

Also, it doesn't make sense to me why it only happens when it's 35+ outside. If it was getting hot all the time, I'd understand, but I don't get why say 20degrees to 35degrees outside temp makes that much of a difference when we are talking about water that is "normal" between 85 and 95.
 

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If it overheats while driving, it isn't the fans since wind/the flow of air cools the engine. That leBes it to the water pump, thermostat, radiator, or blockages in the system. Has the system been bled properly? Has the engine been flushed to make sure there are no blockages? What brand of water pump was put in? What brand of thermostat was put in? Was the water pump installed backwards? Does the car have any codes?
 

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Take a look at the temperature thread in jfof's signature. In summer temps the baseline might be 100-105c.

It would make me nervous though. I would read that thread.
 

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Discussion Starter · #7 ·
Thanks for the replies!

I assume when the radiator has been replaced, twice, the system would have been bled. I've also followed some youtube videos about how to bleed it. IE, turn on the heater leave the cap off the expansion tank and let it heat up.. That's all I can figure out.

Everything is OE brand. No codes. Autologic shows the same temp that the dash does.
Everything was installed by a mechanic, not myself, so I'd assume it's all together properly. But yeah.

I had a read through the link about the cooling system and I'll make sure to test the system when I get a chance.
 

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You can also ask this in the general forum to get much more exposure. Just mention that you have an M3 so people don't confuse it with a non-m
 

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These cars have always been a little tricky to bleed properly. Start by following the video that Bavarian Auto put up on Youtube. However, you should also put the front of the car up on ramps or jack it up. Some would say that there is a design flaw because the heater core unit is higher up than the reservior tank. This causes the cooling system to have hard to get rid off air bubbles in the heater core unit. It also helps to rev your engine up to 3000 rpm a few times throughout the bleeding process once the engine is up to proper temperature.
Is there any leakage at all? Even some small minuscule leak? I would remove bottom splash guard for a couple of days to see if there is any leak after you have gone for a drive.
 

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The S54 cooling system is self bleeding. It is different than non-M cars. If you try bleeding it, you will probably introduce more air into the system.

I would just drain the coolant and start over, it's a lot easier that way than chasing air pockets.
You will need to disconnect the lower radiator hose since there is no drain plug on the radiator. You might want to drain the block too.
Turn the heat on to the max, and fill slowly. That's it.
 

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Discussion Starter · #11 ·
So I did the Fan test according to that pdf.
Unplug sensor, turn car on, wait 15 seconds and turn on AC Compressor. Fan should run at high speed. Mine spins at an idle pace. Normal speed I***8217;d call it. Not the super high ***8220;loud***8221; speed it runs at sometimes.
Which brings me to another point. It very rarely gets to the super loud speed. Even when the needle is reaching the 3/4 dot. Surely it should be turning on to super high sooner than the car getting that hot?

Or am I blowing this all out of proportion?
If the ***8220;normal range***8221; is 85-95. Then 97 isn***8217;t that big a deal?
 

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So I did the Fan test according to that pdf.
Unplug sensor, turn car on, wait 15 seconds and turn on AC Compressor. Fan should run at high speed. Mine spins at an idle pace. Normal speed I***8217;d call it. Not the super high ***8220;loud***8221; speed it runs at sometimes.
Which brings me to another point. It very rarely gets to the super loud speed. Even when the needle is reaching the 3/4 dot. Surely it should be turning on to super high sooner than the car getting that hot?

Or am I blowing this all out of proportion?
If the ***8220;normal range***8221; is 85-95. Then 97 isn***8217;t that big a deal?
Something doesn't seem right...
As I mentioned above, move this to the general forum so the experts comment on this (balidawg, BMW-north, jfoj, etc). They don't check the M3 forum
 

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Thanks for the replies!

I assume when the radiator has been replaced, twice, the system would have been bled. I've also followed some youtube videos about how to bleed it. IE, turn on the heater leave the cap off the expansion tank and let it heat up.. That's all I can figure out.
You have to crack the bleeder.

http://www.m3forum.net/m3forum/showthread.php?t=313594

Follow that procedure. Yes, this is considered "normal" according to the manual. Our temp gauge actually works, unlike in the non-M, which uses a healthy buffer. Running the AC will definitely heat things up, too, which I assume you're doing unless you're a sadist. That's 95F ambient, which is pretty damn hot.

I've never personally seen my gauge go that high, even on 95+ days when giving it the beans. That's anecdotal, though, and doesn't prove that your car is behaving abnormally. The most usual culprit is the viscous fan clutch, which you say has been replaced 3 times. If it is OE, it should be Behr. Behr or Sachs is fine. Worth taking a look to make sure you didn't get ripped off the last time it was replaced. There are tests you can do on the fan. Search m3forum. I'd also go there for advice. The people mentioned in general are great, but they also don't own M3s. People on this forum forget how different these cars are.

Check your fan, replace your coolant if you're due. Be sure to follow the M3 specific procedure for refilling the system. BTW, have you ever used any stop leak products on this car?
 

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Discussion Starter · #14 ·
Sorry, I forgot about the bleed screw, yeah, I let it run until the bubbles stop.

I did put in a "seal tab" or something that my mechanic recommended to see if it fixes any tiny leaks, but it seems not to have, now that we've had another 37degree day.

Funny you mention the fan clutch, I've always thought it was dodgy, because in my e36 320i, if I sit at a set of traffic lights on a hot day and then drive off, I can hear the fan, it sounds like a bus for the first 10-20 seconds, then gets quieter, as the clutch releases and its not pulling as much air.... But in the M3 (e46) it never gets loud, and it never seems to "lock" I can always stop it easily even when the car is running in that 97-100 degree water temp range. Surely it should lock up before the temps get that high?

Again, appreciate the reply!
 

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Sorry, I forgot about the bleed screw, yeah, I let it run until the bubbles stop.

I did put in a "seal tab" or something that my mechanic recommended to see if it fixes any tiny leaks, but it seems not to have, now that we've had another 37degree day.

Funny you mention the fan clutch, I've always thought it was dodgy, because in my e36 320i, if I sit at a set of traffic lights on a hot day and then drive off, I can hear the fan, it sounds like a bus for the first 10-20 seconds, then gets quieter, as the clutch releases and its not pulling as much air.... But in the M3 (e46) it never gets loud, and it never seems to "lock" I can always stop it easily even when the car is running in that 97-100 degree water temp range. Surely it should lock up before the temps get that high?

Again, appreciate the reply!
Did the "seal tab" get put into your engine? :(
 

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But in the M3 (e46) it never gets loud, and it never seems to "lock" I can always stop it easily even when the car is running in that 97-100 degree water temp range. Surely it should lock up before the temps get that high?

Again, appreciate the reply!
After driving on a hot day, my fan is loud as hell pulling into the garage. I wouldn't dare touch it. Sounds like your fan clutch is dead if you're willing to get anywhere near it, let alone touch it, when the engine is that hot. Get a quality replacement and DIY it. Super easy. Pro tip: don't lay it down. The oil will leak out. Fan has to be kept upright. Possible that you got a quality part, but it was mishandled.

And just say no to stop leak products.
 

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Discussion Starter · #17 ·
The seal tab is in there.... Should I flush it to get rid of it?

Yeah, I actually noticed last time that the clutch was lying down on the table where the delivery guy had put it, and there is a big label on it to say keep upright.
But didn't seem to worry the mechanic.

Should I buy one from BMW to ensure it hasn't been lying down?
Have to remember in Aus, it's a little harder to find parts and people that know what they are talking about..
 

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The seal tab is in there.... Should I flush it to get rid of it?

Yeah, I actually noticed last time that the clutch was lying down on the table where the delivery guy had put it, and there is a big label on it to say keep upright.
But didn't seem to worry the mechanic.

Should I buy one from BMW to ensure it hasn't been lying down?
Have to remember in Aus, it's a little harder to find parts and people that know what they are talking about..
Any leak sealer will end up clogging the engine. Get rid of it asap. Even if your fan clutch wasn't working properly, the car shouldn't overheat while driving. Heck, even with a non-functioning fan the car shouldn't overheat as long as there's airflow.

I've said this twice now, move this to the general forum to get more exposure
 

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You don't need to get a BMW branded one. Behr or Sachs were popular when I replaced mine. I'd DIY it and stay away from that mechanic. I'm not familiar with seal tab, but I assume it's a stop leak type product. I wouldn't trust any hack mechanic that would suggest using something like that.

And to reiterate: the car isn't overheating. This is an M3. It's still operating in the "normal" range, although at the high end of normal. The fan clutch is mechanical and the fan ALWAYS spins. It's probably spinning enough to sufficiently cool the motor at idle.
 

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Discussion Starter · #20 ·
Yeah, I'm just wondering how I get around the problem of 10 people handling it before I get it, chances are it would have been sitting on its side. and potentially not work 100%

I was even considering getting an aftermarket in-line temp sensor, so I could double check the sensors where giving the right info.

Oh, and I probably should have mentioned, normal oil temps are maybe 95-100, but sometimes it gets to 110 (cruising) or 115ish (when pushed). And it's usually around 110 when the water temp climbs. But that's not too hot that it would be affecting the water temp, would it?
 
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