Cooling problem, I'm stumped!
 

In the past few weeks/months, I've been getting a low coolant message. I drive the vehicle very little for the most part, so I was just adding coolant every few weeks.
Yes at the same time, I've taken the vehicle on 500km trips, so i know for sure the leak wasnt too bad, or i wouldn't have made it without adding coolant during the trip, which i did not do.

The vehicle wasn't overheating, and I didn't see any leaks, so I thought maybe the engine is taking a little hit of coolant.

But 2 days ago I had my X5 2002 3.0 (M54) overheat badly.
I traced the problem to the lower radiator hose, because I could see the coolant leaking from there.

The factory clamp of the lower hose came partially off, and the coolant was leaking so bad I went through 5 gallons of coolant in 10 minutes.
Luckily I found a Napa store nearby, and put a clamp on top, which allowed me to get home. With a pit spot in between, to cool off and add more coolant to the system.

At home I removed the factory clamps, and installed my own clamps.
No more leaks.
I thought I was done with what was an easy fix.

No quite....

As soon as I started driving it kept overhearing again, and the coolant was going somewhere, disappearing.
I checked, no coolant in the oil, no smoke from the pipe, nothing leaking from under the car.

I bled the system, even parked it at a steep angle, and set the heater on 32C degrees and lowest fan setting.

I noticed something happened with the red floating level in the expansion tank. Somehow it came out of its orbit, so it wasn't centered. But then it disappeared completely, even when the expansion tank is full.
It must've stuck somewhere.

I'm really stumped by this we I've fully replace the coolant system within last 15k km

The other thing that happened when X5 overheated a couple of days ago, the active cruise control light came on the dash and is still there lol

All the hoses are hot to the touch, so I assume the coolant is making its way through the radiator, which means that the thermostat is good then?

I really don't understand where the coolant keeps disappearing. On a 30 minute drive, I have to stop 3 times to cool off the vehicle, open the expansion cap, and add a good few liters of coolant.

I have 1.4 bar cap from E34, which means the system will vent sooner if it overheats.
Never had any problems because of it before, neither with E39 not 53.

I can't figure out where the coolant is disappearing and why I can't drive the vehicle for more than 10 minutes without overhearing.

I'm watching the temperature live, and it just keeps going up until 125 where it just gives a massive warning. I try to turn off the vehicle before that and cool it off.

This is just driving me nuts :(

Loss of coolant without steam is not good but with low pressure cap you may be venting without realizing.

A recent m54 very similar situation was from the pump impeller failing. It will break free from the axle and not spin. No flow= overheat. Overheat over pressure vent through low pressure cap.

Hopefully that's your issue else it could be the head gasket but you should see lots of white smoke if that's the case.

I'm not sure the easiest way to diagnose. I forget if the pump has houses out front but you may be able to confirm the impeller is intact or not though the hose goesin or goesout without having to remove the pump itself (but of course draining enough coolant).

Good luck.

But I drove for many many months with this cap without issues. I don't understand. Lots of people convert to this cap and I haven't seen anyone report any issues.
In fact GAS made 1.2 bar cap and countless people used it without any issues.

As for the impeller, I have a metal one, so it shouldn't break but who knows!

Out of desperation I purchased a thermostat from the dealer today, but I don't think it's the thermostat.
If the thermostat was stuck closed, the coolant wouldn't make it to the lower and upper hoses right?

Cooling problem, I'm stumped!
 

Cap unrelated to failure and possibly helpful in that it will cause an obvious fault at a lower pressure then will cause damage to the reservoir and other plastic parts is my understanding of why people do it.

I don't remember what the path of the coolant when tstat is stuck closed but I wouldn't be too surprised if tstat opens enough to get some water though too radiator.

Metal impeller is good but if the impeller broke free from the axle it won't push wate also "hot" is very relative if you didn't actually measure the temps and just put hand on them.

I've had somewhat of a similar experience with my 05. X3 m54.
The problem...the fan would not kick on. Now the fan functioned fine on another X3. But not on mine. Using the scanner I cleared the fault code , and wouldn't you know it the fan kicked on. And no more temp arm traveling to the red.


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I bled the system as much as I can and drove home 30 minutes. The temperature was very slowly creeping up.
When I stop, the temperature does drop. There's lots of steam coming from under the hood and wheel well, temperature is about 110-120 Celsius.
Just as my trip was about over, 30min or about 50 km, I got the message of low coolant displayed on the dash.
I dont get it what's happening with the coolant lol, is it evaporating, and why?

https://i.ibb.co/PhQTzr7/20240405-202508.jpg
https://i.ibb.co/z8dbq0B/Screenshot-...503-Chrome.jpg
https://i.ibb.co/Qj7pb5h/M52-TU-Coolant-Flow.jpg

So far the theories are either a partially stuck open thermostat, or broken water pump?

I replaced the Auxiliary Fan last year, so it should be working. In either case, I don't think the aux fan works when the vehicle is driving. Clutch fan and speed is normally enough. So as far as I know it only kicks in when stationary.

Webasto connector plug/hose leak? Even without a Webasto it still has the connector (plug/hose) for it....


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I dont know where the webasto hose would be, but if anything is leaking at this rate, I would expect to see the leak on the ground with the vehicle running, but i don't see a leak. I want to see a leak! Then I can trace it. For now no leak, just disappearing coolant.
I think soon I will just be filling it with tap water, I spent $100 on coolant in 2 days

The only other idea I have is the 2 pipes under the intake manifold. But I have replaced them.
Maybe they're leaking the coolant on the engine, which then evaporates. But I would expect the smoke to be coming from there, instead it's coming from the coolant reservoir area...

Maybe I have something like this
https://youtube.com/shorts/qSipz__ip...3HsN0EzubzVhju

But at the rate I'm loosing coolant, I feel I would still have something dripping on the floor.

I understand the initial overheat. The system had air in it, which caused it to overheat, thus building the extra pressure.

This in turn probably blew the hose from under the factory clamp on the lower radiator hose.
So basically due to building pressure, the weakest link gave up.
If the hard tubes were leaking, I would've expected them to give out first. This is quite a challenge to figure out...

Remove the lower plastic air dam. I'm surprised how much water it can hold before dripping. It's how I confirmed a coolant leak. Mine currently leaks at the transmission oil cooler. If the transmission lines move too much, the cooler teeters. When the cooler teeters off center, the lower seal comes out and leaks.

This one?

https://i.ibb.co/ZxF7Kc2/Screenshot-...838-Chrome.jpg

Removed it right away to make it easy to look for leaks but still nothing.

I need to buy a pressure testing kit or smth, just not sure which one will fit bmw expansion tank

This thread shows a couple of homebrewed solutions to pressurize the cooling system.

https://xoutpost.com/bmw-sav-forums/...ystem-e53.html

Yes, remove the "belly pan". Get this test kit from Harbor Freight when it's on sale. The yellow adapter fits the X5 tank perfectly.

Thanks skewel, I'm going to look if I have an extra cap laying around.
I can probably just use an electric tire pump to pressurize it?
Testing through the bleeder screw would be easier, but I'm afraid that the cap will depressurize the system before enough pressure build?

I guess my reservoir cap is rated at 1.4 bar, which is 20 psi, and only 15 psi is needed to pressurize the system for testing, from what I read. So I would be good to use the bleeding screw

Being in canada, the easiest way to purchase a kit would be on Amazon.ca but a lot of them have poor description, so it's hard to tell which one has a bmw adapter.

In the meantime I'll try this

https://i.ibb.co/H7XjFH4/20240406-104541.jpg
https://i.ibb.co/Kxwzx18/20240406-104527.jpg

I think I found a minor leak, which maybe looked minor, but was major when the vehicle was running lol. My own doing, where I spliced a heater into the lower radiator hose. Tightened the clamps, and fixed the leak as far as I can tell for now.

Then I pressured the system to about 20 psi.
If I push past 20 psi, I can hear the radiator cap releasing the air. So my ryobi tire inflator gauge must be pretty accurate.

While looking for the leak I found my own radiator cap which flew away lol. It was actually maybe 1-2 years old only. Interestingly, with this radiator cap, I could hear air escaping even if I only pressurized the system to 15 psi. So I think this cap is defective, maybe because the system overheated originally with this cap on it, and the overhead was at least to 140 Celsius, maybe the cap got damaged.

The other cap holds the air at 20 psi, no leaks at all.
I listened but could not hear any air escape. That's with a cold engine.
After 10 minutes, psi dropped from 20 to 15 psi.
After 20 minutes, pressure was down to 10 psi.
After 30 minutes, pressure was down to 7 psi.
I'm not sure if that's normal, but back pressure is slowly releasing back through the pump.

One constant in all of this mess is driving.
Took it for a drive, after about 15 min, temperature slowly rising. Let it climb to 110 degrees, pull over with vehicle running, stay idling, temperature dropped to 93C slowly. I raised rpm to 3000 and waited a few minutes, temperature is climbing past 100 again.
Let idle for another 15 minutes, temperature down to 95C.

I check the aux fan, it's not running. So I know it's not the aux fan cooling things down.
Temperature outside +4C.

This is weird. I have a situation where I'm overheating when driving, but normal when idling.
I found a ton of topics "overheating when idling" but not overheating when driving, but not overheating when idling", like in my situation.
After idling in total about 30 minutes, with the belly pan removed, I don't see any leaks ok the ground.

So this is weird.

I'm now thinking back how it all started.
The vehicle overheated, obviously raising the pressure, causing the radiator cap to allow the pressure to escape, and causing the lower radiator hose clamp to come off.
This started the quest for a leak, which i found on the lower radiator hose and fixed.
Hard to say if the leak was caused by the overheating, or if it was there before.
But definitely I had a small leak for the past few months, and I've been seeing the message of low coolant, but vehicle never overheated. I even took it on trip of 500km.

So maybe I had a small leak at the radiator hose, which became a big leak when it overheated.

But now it seems I'm not loosing any coolant, at least when I'm idling. Or maybe I'm loosing coolant, but it's not leaking on the ground. Just idling at 95C, there's nonsmoke coming from X5.
I start driving, within 3 minutes or so, my temperature is up to 115C from 95C

So the mystery is why when rpm is higher, the vehicle overheats. This is pointing me in only one direction, broken water pump. I don't see any other explanation for this behavior.
Or maybe the thermostat only opens partially, like 10% or smth.
I'm inclined to replace both the thermostat and the water pump.

New ≠ fixed you have to follow the symptom which is pump or something blocking the flow.

At idle the car is pushing 5-6hp and driving prob closer to 15-20 steady state to 225 full throttle. A lot more heat to dispose of.

If the temp is stable at idle there is flow so tstat not completely blocked and opens when it shoild if temp is stable.

I haven't seen example thread of the metal impeller coming loose from the shaft but it exactly matches your symptoms.

I think you can pull off the hose and reach in with a tool or finger hold the impeller and turn the pulley to confirm impeller is loose on the shaft or not.

Ahhhh imgbb is down, can't post photos...

I took everything out. Trying to test the new thermostat I bought from bmw. I pour boiling water on it, but it's not opening. Not sure what temp it's supposed to open at? It's one piece with the housing, so makes it more complicated because the thing is so big, doesn't fit in a glass lol

https://imgtr.ee/images/2024/04/06/d...073315a0c.jpeg
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You can use a pot to test the wax motor. I'm thinking about 95c open temp so below boiling

Tried boiling water, no luck. As soon as you start pouring water, it's already 90C. So thermostat never opened.

Turns out you can connect 12v and it will open.
Tested the new thermostat, opened after a few minutes.
Tested old thermostat, never opened. Clearly it was broken and the wax spilled out and didn't work anymore.

Seems pretty conclusive. Will be great to see report that it's working properly.


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Should've never "upgraded" to aluminum thermostat housing.

https://imgtr.ee/images/2024/04/06/2...4310b01d3.jpeg
https://imgtr.ee/images/2024/04/06/3...7f71d07df.jpeg
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Yea gonna put everything together now.
While doing this job I also took out all the spark plugs and poured a bunch of acdelco in each cylinder to clean the piston rings. If all goes well, this will completely eliminate the oil consumption, which is already minimal with ccv mod. Then will put some engine flush, run it for 15 min and replace engine oil.
Gotta get this baby ready for tomorrow's 250km trip!

https://ibb.co/gmcG8ZD

Flushed the engine, replaced oil, took it for a spin, coolant temperature doesn't go over 90C!
SUCCESS!

Still lots of vapor/smoke from under the hood, hopefully it's just the coolant that leaked is evaporating.