Has anyone experienced black deposits (residue?) in the low temp (aux cooling) reservoir for the intercooler? Does anyone know what this could be? I recently purchased the car a few weeks ago.
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Black in the aux cooling reservoir
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joshuawheat
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@ALFAOFFROAD this maybe totally unrelated but I had a faulty thermostat on beamer that gave me similar problem of not warming up properly. In the summer it was okay but when it was cold, the engine ran really rough and had hard time keeping it running smooth. I know you think it's relay switch but have you seen this video? Alfa Romeo Stelvio/Giulia 3way valve/ thermostat install
no idea if that's the same issue but I'm guessing that could be one of the reasons why your engine is not warming up as it should? Hope your switch arrived....
no idea if that's the same issue but I'm guessing that could be one of the reasons why your engine is not warming up as it should? Hope your switch arrived....
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Well what generally happens is the pump will run still but the flow will be weaker due to higher resistance in the relay for the pump. It can't keep up with the demand from the ECU and as a result, the ECU just pulls timing and cuts power.
Just to give some insight and try and fix a ton of misinformation presented let me try and help here....
This is not the case.
the low temp loop cools the intake air charge. It does not interact with the high temperature coolant loop that cools the engine.
This is incorrect.
There are two radiators in the stelvio that are solely LOW TEMP coolant loop heat exchangers. The high temperature loop has its own radiator. See below.
Low temp loop:
![Image]()
These radiators above indicated as R1 and R2 are used SOLELY in the low temperature loop.
Below, here is the high temperature loop btw that has completely separate coolant loop, separate radiators and separate pump....
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These radiators R1 and R2 are completely different radiators than those in the low temp loop. If you look under your hood you'll see three main center radiators.
Now back to the low temp loop that we are discussing.
The low temp loop is used to cool the intake air charge.
Our intake air gets super heated by the turbocharger which under even part load can see 25psi of boost at just 2200rpm to provide low end torque.
We consequently have an intercooler brick at the intake manifold that is liquid (coolant) cooled from the air that passes over this loops radiators (heat exchangers) at the front of the vehicle.
This is incorrect
A charge air cooler or intercooler can be air to air, air to water, etc. The names can be used interchangeably. Yes you can have an air to air charge air cooler.
Without intercooling our intake temps can sky rocket to 200 degrees Fahrenheit.
This puts the vehicle into reduced power (timing tables get reduced due to IAT offset tables).
Even with reduced timing and power you still see extreme intake temps without the intercooler pump working you just hopefully don't see dangerous knock which the ECU is protecting against.
This will primarily be noticed by drivers as feeling reduction in wide open throttle acceleration performance. Indeed you'll be down about 50 peak hp ....but if you're just cruising around town using 100hp then you may not notice for quite some time.
In addition to providing the intercooling heat management fluid the low temp coolant loop is also used to cool the physical turbo itself. This is very uncommon (usually it's the high temp coolant loop) but in our cars it does.
See the green section of the low temp loop below...
![Image]()
Bottom line is it's important to make sure it's functioning.
Now it probably has absolutely nothing to do with sediment in your high temp radiator overflow bottle lol but still an important unrelated topic.
This is not the case.
the low temp loop cools the intake air charge. It does not interact with the high temperature coolant loop that cools the engine.
This is incorrect.
There are two radiators in the stelvio that are solely LOW TEMP coolant loop heat exchangers. The high temperature loop has its own radiator. See below.
Low temp loop:
These radiators above indicated as R1 and R2 are used SOLELY in the low temperature loop.
Below, here is the high temperature loop btw that has completely separate coolant loop, separate radiators and separate pump....
These radiators R1 and R2 are completely different radiators than those in the low temp loop. If you look under your hood you'll see three main center radiators.
Now back to the low temp loop that we are discussing.
The low temp loop is used to cool the intake air charge.
Our intake air gets super heated by the turbocharger which under even part load can see 25psi of boost at just 2200rpm to provide low end torque.
We consequently have an intercooler brick at the intake manifold that is liquid (coolant) cooled from the air that passes over this loops radiators (heat exchangers) at the front of the vehicle.
This is incorrect
A charge air cooler or intercooler can be air to air, air to water, etc. The names can be used interchangeably. Yes you can have an air to air charge air cooler.
Without intercooling our intake temps can sky rocket to 200 degrees Fahrenheit.
This puts the vehicle into reduced power (timing tables get reduced due to IAT offset tables).
Even with reduced timing and power you still see extreme intake temps without the intercooler pump working you just hopefully don't see dangerous knock which the ECU is protecting against.
This will primarily be noticed by drivers as feeling reduction in wide open throttle acceleration performance. Indeed you'll be down about 50 peak hp ....but if you're just cruising around town using 100hp then you may not notice for quite some time.
In addition to providing the intercooling heat management fluid the low temp coolant loop is also used to cool the physical turbo itself. This is very uncommon (usually it's the high temp coolant loop) but in our cars it does.
See the green section of the low temp loop below...
Bottom line is it's important to make sure it's functioning.
Now it probably has absolutely nothing to do with sediment in your high temp radiator overflow bottle lol but still an important unrelated topic.
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Important part:
The car doesn't cut timing and reduce power due to sensing a problem anywhere other then the engine starts getting hot.
This is an all aluminum engine...in no way should it ever get too hot, even by a few degrees. One time won't hurt anything ....100 times will. Something will eventually warp due to heat, some gasket will fail.
However long before the metal wears, or gaskets decompose fully,the rubber in the coolant hoses will begin to degrade from the heat. I believe that rubber is what is in the reservoir and should serve as an early warning that engine temps are slightly elevated.
I haven't been tripping about my oil temp climbing one bar, however..it never left the back of my mind and if it happened again this year I was going to figure it out or die trying (still will if this doesn't do it) because even one bar of extra temp for five minutes, three times a year, will kill the engine eventually. Will kill any aluminum engine eventually.
Also.. good to know, the cooling system between the Giulia and Stelvio aren't exactly the same, I don't know the exact differences just going off what Alfa says on the diagram for the Stelvio. In the Stelvio the secondary radiator have both hot and low function indifferent parts of the radiators.
Look at the diagram, the overall radiator is for the LT according to the pictures on page 5 however page 6 then shows the system from a different angle and reveals a section on the side of the radiator that is used for HT cooling (R2 in the legend).
Page 5 look at item 6
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Page 6, look at R2
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The legend is on page 7, because Alfa likes to be obtuse.
More so look at the system diagrams and see both have item "T" bypass solenoid valve. Which is the item discussed in the video Alfie linked to, which is a complex valve..called in that video a "3 way coolant circuit". What 3 way does it control? High, low and overall. Each system has its own reservoir however the fluid can between systems as needed. The fluid is all the same fluid, the reservoirs are there to be sure there is always extra where needed, when needed.
The best way to think about it IMO, while there are two sides and high and low temp, both sides are part of the same system and effect each other. They are not independent of each other, they work together to achieve one goal of cooling the engine.
BTW I also thought it was HT only originally due to things posted elsewhere. The reason some people have said such things is because....it is HT. The reason other say other is because It's also LT. It is both depending on which section being discussed but it's all one cooling system. Don't overthink it.
I don't care where the residue is.. I care it's there. Lots of variables could factor in to where it winds up, that has nothing to do with why it happens.
Will the relay fix my issues? Maybe not.. but maybe, worth trying. Tracking shows it should be here this afternoon, yay!
The car doesn't cut timing and reduce power due to sensing a problem anywhere other then the engine starts getting hot.
This is an all aluminum engine...in no way should it ever get too hot, even by a few degrees. One time won't hurt anything ....100 times will. Something will eventually warp due to heat, some gasket will fail.
However long before the metal wears, or gaskets decompose fully,the rubber in the coolant hoses will begin to degrade from the heat. I believe that rubber is what is in the reservoir and should serve as an early warning that engine temps are slightly elevated.
I haven't been tripping about my oil temp climbing one bar, however..it never left the back of my mind and if it happened again this year I was going to figure it out or die trying (still will if this doesn't do it) because even one bar of extra temp for five minutes, three times a year, will kill the engine eventually. Will kill any aluminum engine eventually.
Also.. good to know, the cooling system between the Giulia and Stelvio aren't exactly the same, I don't know the exact differences just going off what Alfa says on the diagram for the Stelvio. In the Stelvio the secondary radiator have both hot and low function indifferent parts of the radiators.
Look at the diagram, the overall radiator is for the LT according to the pictures on page 5 however page 6 then shows the system from a different angle and reveals a section on the side of the radiator that is used for HT cooling (R2 in the legend).
Page 5 look at item 6
Page 6, look at R2
The legend is on page 7, because Alfa likes to be obtuse.
More so look at the system diagrams and see both have item "T" bypass solenoid valve. Which is the item discussed in the video Alfie linked to, which is a complex valve..called in that video a "3 way coolant circuit". What 3 way does it control? High, low and overall. Each system has its own reservoir however the fluid can between systems as needed. The fluid is all the same fluid, the reservoirs are there to be sure there is always extra where needed, when needed.
The best way to think about it IMO, while there are two sides and high and low temp, both sides are part of the same system and effect each other. They are not independent of each other, they work together to achieve one goal of cooling the engine.
BTW I also thought it was HT only originally due to things posted elsewhere. The reason some people have said such things is because....it is HT. The reason other say other is because It's also LT. It is both depending on which section being discussed but it's all one cooling system. Don't overthink it.
I don't care where the residue is.. I care it's there. Lots of variables could factor in to where it winds up, that has nothing to do with why it happens.
Will the relay fix my issues? Maybe not.. but maybe, worth trying. Tracking shows it should be here this afternoon, yay!
@bhvrdr and @ALFAOFFROAD I see the diagrams and it's making sense to me now. So it is the turbo water pump that relay is controlling, correct? You know, You guys are basically saying the same thing. In my non-technical view, you both are saying turbo coolant water pump is failing or the switch is bad. Sorry.. I ignored all the technical reasons. just what's broken. LOL
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Eh. I ignore him.. no clue what he says anymore. More peaceful that way.
I'm not sure @ALFAOFFROAD but my turbo reservoir level never changed for past 4 years. Which leads me to believe that it is on its own system whereas the left reservoir, I do see some changes once in a blue moon. In other words, they play independently. I think his first two diagram is pretty much clear and tells me that's the case. Now the 3 ways things... That's just beyond me but I do not see coolants being transferred from Turbo to Main..
This is false. Engine oil and coolant temp will cause a cel yes.
But the ECU has timing based maps that are offset by INTAKE AIR TEMPERATURE.
I've calibrated these maps before.
That is why I posted the diagram for the stelvio system.
This is the stelvio s which has the additional low temp heat exchanger (R2 on the passenger side of the vehicle) and a low temp center radiator (R1)
This is the giulia that only uses a main low temp center radiator.
I have already corrected you on this. No they do not.
Look at the diagrams and look under your hood.
There are two gigantic center radiators. One for low temp side and one for high temp. They do not connect.
There are two side mount radiators. One for high temp and one for low temp. They do not connect.
Not meaning to insult you at all but you've really got to get better at reading diagrams. The diagrams are labeled low temp and high temp because these are two completely separate systems and two completely different diagrams.
As an example the R2 for the low temp and the high temp are not even on the same side of the vehicle. These are separate radiators for two completely separate coolant loops.
Again all you had to do was ask me and I'm happy to tell you.
The three-way valve is in the low temp circuit only as the diagram clearly shows and as you can see simply by looking under your hood.
The valve allows you to bypass the heat exchanger and loop the low temp water or to run it through the heat exchanger. It is a thermostat of sorts for the low temp loop.
Three way valve in low temp loop bypassing....
No bypass...
There is absolutely no valve or hose that connects the two completely separate loops.
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They play both. Normally independent.. something happens .. not independent.
Another important part:
The relay box all this is contained in is labeled as only existing in the 2.9 and I have the 2.0, the diagrams for it show 5 relays, and there are 6 in it in my car.
Could give 500 other examples of things like this in cars. Seriously .. focus on what's there and what it does. The names are not important and very likely this relay does more than what it is labeled to. No argument it's maddening, why its best to focus on problems and solutions.
Problem: my cooling system isn't letting the engine warm up fast enough and isn't cooling properly under high temp/load. Power is also lower, but is that related? Maybe.
Other problem: a relay used by the cooling system isn't working.
Solution: change the relay and see what happens.
The rest ....fun to talk about but really, who cares? For real.
Another important part:
The relay box all this is contained in is labeled as only existing in the 2.9 and I have the 2.0, the diagrams for it show 5 relays, and there are 6 in it in my car.
Could give 500 other examples of things like this in cars. Seriously .. focus on what's there and what it does. The names are not important and very likely this relay does more than what it is labeled to. No argument it's maddening, why its best to focus on problems and solutions.
Problem: my cooling system isn't letting the engine warm up fast enough and isn't cooling properly under high temp/load. Power is also lower, but is that related? Maybe.
Other problem: a relay used by the cooling system isn't working.
Solution: change the relay and see what happens.
The rest ....fun to talk about but really, who cares? For real.
This is probably the sixth post you've made saying that the high temp and low temp loops are connected..
Again there is absolutely no connection between the two loops.
I actually run a different liquid mixture in my low temp loop in order to aid in intercooling and it is a completely different color than my main engine loop and guess what they stay a completely different color because they are not connected in any way whatsoever.
You know...
I don't see the hybrid turbo yet... or is it there?
That was an old video I made. I'd have to check the date stamp to even know.
The beauty of that hybrid turbo is that it is the OEM turbo housing so you literally cannot tell the difference to include even the turbo identification plate on the turbo will match OEM.
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The turbo interaction with the system is way down on page 20-something of that coolant(2) pdf. You'll see it there, otherwise the turbo isn't technically part of the cooling system so it isn't labeled I think.
I'm not sure what you're saying. what is your question?
The turbo itself is cooled by the low temperature loop as well.
Again completely separate from the high temperature loop which cools the engine.
I can tell you this first hand and show you pictures first hand because I've removed the turbo and the low temp circuit and all of the plumbing that goes to it and then reinstalled it before.
Do you still have questions about this?
So if the relay fails or is failing then you get reduced flow in the low temp circuit resulting in higher intake air temps which causes the ECU to pull timing. Makes sense. So if you have multiECU or other tool you could monitor IAT to possibly tell if you have a bad relay.
What doesn't make sense to me is why Alfa put the turbo on the low temp circuit. That seems like a recipe for early turbo failure.
What doesn't make sense to me is why Alfa put the turbo on the low temp circuit. That seems like a recipe for early turbo failure.
You are spot on in both cases.
I've had multiple people contact me about "my tune doesn't seem to make consistent power"
The first thing I do is show them how to data log their intake air temperatures and timing.
In almost every single case it has been a bad relay.
And yeah I agree it's absolutely bizarre that they're cooling the turbo with the low temperature loop. That said it is also an oil cooled turbo as well and for some reason we've been pretty lucky with these turbos with the primarily failure mode being the wastegates.
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The circuits aren't really that separate is why. Think of it like left and right hands, which are entirely separate one being dominant over the other. However something goes wrong with one you can use the other. Similar concept, if a bit simplified.
![Image]()
New relay is all shiny and pretty, installed it and tested everything I can right now (isn't hot enough to have the issue with temps climbing yet).
Car is accelerating with more authority, significantly more compared back to back. It also got right up to operating temp in minutes and stayed there like a rock. To be more clear, I haven't seen 4 bars on my temp gauge since September (?) unless I drive at least an hour and even then it might drop back down given variables. After changing the relay I had 4 bars in just under 10 minutes and it did not change over the course of an hour of driving. Like I said, not since Sept at least. (Why didn't I look into it? Ehh, its been cold and the car is aging, being a bit cool doesn't damage things like being hot.. really just rationalizing because I don't like working on my own car and assumed it was the thermostat so wait till it needs to be done. Glad it wasn't the thermostat, that isn't the hardest job but still this was easy as easy gets)
Honestly after driving it with the malfunctioning relay then with the working one the difference was more then I remembered in power, especially from a dead stop. Makes me wonder if some of the people/person (you know who) who said they test drove a used Stelvio and found it slow, and nowhere near the claimed power, drove one with this relay malfunctioning. Also some of the people who really seem to have problems with the initial acceleration of the car.. might have a bad relay. (Should add, people with used Stelvio's who have issues.. doubt a new one will have any bad relays) Should add to be clear, the acceleration was fine at the top of the band before and about the same as now, but lower down where the turbo is.... There is a lot more urgency now. It obviously has been failing slowly for awhile, back to back ... No way I wouldn't notice. Its embarrassing I didn't as-is.
Obviously at least one person will say that's impossible. I say try it, cheap and easy fix if it works, and if it doesn't.. still cheap and easy not much of a loss.
New relay is all shiny and pretty, installed it and tested everything I can right now (isn't hot enough to have the issue with temps climbing yet).
Car is accelerating with more authority, significantly more compared back to back. It also got right up to operating temp in minutes and stayed there like a rock. To be more clear, I haven't seen 4 bars on my temp gauge since September (?) unless I drive at least an hour and even then it might drop back down given variables. After changing the relay I had 4 bars in just under 10 minutes and it did not change over the course of an hour of driving. Like I said, not since Sept at least. (Why didn't I look into it? Ehh, its been cold and the car is aging, being a bit cool doesn't damage things like being hot.. really just rationalizing because I don't like working on my own car and assumed it was the thermostat so wait till it needs to be done. Glad it wasn't the thermostat, that isn't the hardest job but still this was easy as easy gets)
Honestly after driving it with the malfunctioning relay then with the working one the difference was more then I remembered in power, especially from a dead stop. Makes me wonder if some of the people/person (you know who) who said they test drove a used Stelvio and found it slow, and nowhere near the claimed power, drove one with this relay malfunctioning. Also some of the people who really seem to have problems with the initial acceleration of the car.. might have a bad relay. (Should add, people with used Stelvio's who have issues.. doubt a new one will have any bad relays) Should add to be clear, the acceleration was fine at the top of the band before and about the same as now, but lower down where the turbo is.... There is a lot more urgency now. It obviously has been failing slowly for awhile, back to back ... No way I wouldn't notice. Its embarrassing I didn't as-is.
Obviously at least one person will say that's impossible. I say try it, cheap and easy fix if it works, and if it doesn't.. still cheap and easy not much of a loss.
Now this is the seventh time you have said this and it is false information.
There is absolutely no connection between the two loops.
The two loops are 100% separate there is no hose or valve or crossover of any sort whatsoever that connects them both.
Is this clear yet?
It wouldn't be a normal day on this forum if he wasn't doing this, right?
Anyway, thank you for your attention to detail and willingness to engage on this forum. You have significantly more patience than I do.
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