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Discussion Starter · #1 ·
I have a 2017 red sport q50 with 65k miles that I purchased back in November 21. I believe I still have some factory warranty left and I have the extended max care by Infiniti. I got one of the turbos replaced at about 55k miles. A couple days ago when I put the car under moderate acceleration I would hear a quick chirp, but it wouldn’t happen every time. I was checking my oil level yesterday and realized the coolant reservoir for my turbos was below the minimum level and i couldn’t even tell that there was any coolant in there. I got more coolant added in to fill it to the max fill line, and I haven’t heard the chirp since. I’m not sure how coolant could have just escaped from the reservoir and I haven’t noticed any signs of leaking under the car. Where could it have gone… is this something I should be worried about and have it checked considering I had issues with the turbos before? They only replaced 1 turbo, and I’ve heard that with some cars when 1 goes bad the other one will usually be affected as well. Does anyone have any insight on this?
 

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Id check the drive belt, i had a similar noise under moderate acceleration that made me think it might be a turbo going. Replaced the belt first since that was cheap and the noise went away
 

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A chirping noise from under the hood is almost always the belt. The more concerning issue is the missing coolant. Now, it could be that when they replaced the turbos, they lost some and forgot to top it off. But between the missing coolant and the belt chirp, I would take a very close look around your multi-way valve for even the slightest hint of a leak. When the multi-way valve leaks, it tends to get on the belt, causing it to slip on its pulleys, which creates that chirping noise you described.
 
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A chirping noise from under the hood is almost always the belt. The more concerning issue is the missing coolant. Now, it could be that when they replaced the turbos, they lost some and forgot to top it off. But between the missing coolant and the belt chirp, I would take a very close look around your multi-way valve for even the slightest hint of a leak. When the multi-way valve leaks, it tends to get on the belt, causing it to slip on its pulleys, which creates that chirping noise you described.
I'm not too familiar with the cooling systems, but does the multi-way control valve regulate the intercooler coolant?
 

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I do believe so. Hence multi-way. One way for the engine coolant, one way for the intercoolers. If I’m wrong, someone please correct me!
 

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A chirping noise from under the hood is almost always the belt. The more concerning issue is the missing coolant. Now, it could be that when they replaced the turbos, they lost some and forgot to top it off. But between the missing coolant and the belt chirp, I would take a very close look around your multi-way valve for even the slightest hint of a leak. When the multi-way valve leaks, it tends to get on the belt, causing it to slip on its pulleys, which creates that chirping noise you described.
I'm not concerned. If his turbo was replaced, then the system was refilled and it has been reported multiple times on here that you often have to top off the system a couple times as it works the air bubbles out. I had to do this after my turbos were replaced.

For the chirping, as has been stated, check and / or replace your drive belt. Also verify your water pump isn't leaking coolant onto the belt.
 

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I'm not too familiar with the cooling systems, but does the multi-way control valve regulate the intercooler coolant?
I do believe so. Hence multi-way. One way for the engine coolant, one way for the intercoolers. If I’m wrong, someone please correct me!
The CAC coolant flow is not regulated by the multi-way control valve. That coolant path remains open all the time. The ECM controls the CAC flow based on the intake air temperature sensor and CAC coolant temperature sensor. When the temperature difference between those two sensors becomes great enough, the ECM switches the CAC pump from low to high speed for single pump operation or operates the second CAC pump (RS). The radiator cooling fan control modules will ramp up fan speed also based on the ECM's memorized control mapping.

The multi-way control valve regulates coolant flow to the engine oil cooler, ATF warmer, and cabin heater in addition to the radiator based on temperatures and ECM programming.
 
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The CAC coolant flow is not regulated by the multi-way control valve. That coolant path remains open all the time. The ECM controls the CAC flow based on the intake air temperature sensor and CAC coolant temperature sensor. When the temperature difference between those two sensors becomes great enough, the ECM switches the CAC pump from low to high speed for single pump operation or operates the second CAC pump (RS). The radiator cooling fan control modules will ramp up fan speed also based on the ECM's memorized control mapping.

The multi-way control valve regulates coolant flow to the engine oil cooler, ATF warmer, and cabin heater in addition to the radiator based on temperatures and ECM programming.
Thank you for the correction! Great info as always, Av.
 

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Discussion Starter · #9 ·
I just got it looked at today at an Infiniti dealer for the problems described. When my first turbo was replaced, it was the right turbo. I was told by the service advisor that the left one is now what's making noise, and it's on its way out. I was told the intercooler is working fine, and the reason for the low coolant is because the turbos eat up coolant when they're going bad. Can anyone attest to the coolant statement? I work at another brand dealership as a salesman, so I know first hand how messed up service departments are. Some of the mechanics are great, others aren't very good. Same with the service advisors, some know what they're talking about, others bullshit. The extended warranty is a no brainer though, and as bad as I would like to do the work myself to make sure everything's done the right way; after having to replace 2 turbos my pockets feel a lot better with the extended warranty. Instead I just have to make sure what they're doing makes sense, verify the advisor knows what he's talking about, and hope someone who is knowledgeable is working on it.
 

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That usually is true. Sometimes it’s a leak, sometimes they just burn the coolant up.
 

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The Charge Air coolant doesn’t go anywhere near the turbos.
 

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I just got it looked at today at an Infiniti dealer for the problems described. When my first turbo was replaced, it was the right turbo. I was told by the service advisor that the left one is now what's making noise, and it's on its way out. I was told the intercooler is working fine, and the reason for the low coolant is because the turbos eat up coolant when they're going bad. Can anyone attest to the coolant statement? I work at another brand dealership as a salesman, so I know first hand how messed up service departments are. Some of the mechanics are great, others aren't very good. Same with the service advisors, some know what they're talking about, others bullshit. The extended warranty is a no brainer though, and as bad as I would like to do the work myself to make sure everything's done the right way; after having to replace 2 turbos my pockets feel a lot better with the extended warranty. Instead I just have to make sure what they're doing makes sense, verify the advisor knows what he's talking about, and hope someone who is knowledgeable is working on it.
Did you ever top off the coolant and then see if it ever goes too low again over time? I said it previously above that when the charge air coolant is replaced, there have been numerous reports on hear that topping it off 1 to 3 times afterward often happens. This is because the air bubbles have to work themselves out. It all depends on how well the system was "burped" when refilling.

I wouldn't sweat the coolant in the CAC system unless you've taken steps to top off and monitor over time.
 

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Discussion Starter · #13 ·
Did you ever top off the coolant and then see if it ever goes too low again over time? I said it previously above that when the charge air coolant is replaced, there have been numerous reports on hear that topping it off 1 to 3 times afterward often happens. This is because the air bubbles have to work themselves out. It all depends on how well the system was "burped" when refilling.

I wouldn't sweat the coolant in the CAC system unless you've taken steps to top off and monitor over time.
It's only been a little over a week since I first noticed this. I was worried that the turbos were running on very low coolant for god knows how long. After topping it off, it's been good since; so I would assume there's no leaks. Wouldn't they need to bleed the coolant in the turbos when they're replaced, already removing most of the air bubbles? I just found it hard to believe that there was that much air in the loop to the point that the reservoir is very low... If that's the case, there must've been a lot of air in the system. I'm thinking that my turbos haven't been getting the proper cooling for the past 10k or so miles since replacement.
 

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The Charge Air coolant doesn’t go anywhere near the turbos.
Correct. The coolant that is routed through the turbos is engine coolant, not the IC coolant. Hopefully OP is observing the level in the correct reservoir (driver's side).
 

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Discussion Starter · #15 ·
Correct. The coolant that is routed through the turbos is engine coolant, not the IC coolant. Hopefully OP is observing the level in the correct reservoir (driver's side).
The reservoir that had very little coolant in it was the intercooler reservoir (passenger side). When I noticed the problem I immediately brought it to the Infiniti dealer and one of the techs was nice enough to check it real quick and add coolant for me. The drivers side level was ok. He told me that the passenger side reservoir was for the turbos. If what your saying is the case, then the low fluid couldn't be from the turbos burning it off... Does anyone have a link that will give me useful information on how the intercooler loop is set up?
 

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The reservoir that had very little coolant in it was the intercooler reservoir (passenger side). When I noticed the problem I immediately brought it to the Infiniti dealer and one of the techs was nice enough to check it real quick and add coolant for me. The drivers side level was ok. He told me that the passenger side reservoir was for the turbos. If what your saying is the case, then the low fluid couldn't be from the turbos burning it off... Does anyone have a link that will give me useful information on how the intercooler loop is set up?
The RS has the Type 1 CAC configuration:

Rectangle Font Parallel Slope Schematic
 
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It's only been a little over a week since I first noticed this. I was worried that the turbos were running on very low coolant for god knows how long. After topping it off, it's been good since; so I would assume there's no leaks. Wouldn't they need to bleed the coolant in the turbos when they're replaced, already removing most of the air bubbles? I just found it hard to believe that there was that much air in the loop to the point that the reservoir is very low... If that's the case, there must've been a lot of air in the system. I'm thinking that my turbos haven't been getting the proper cooling for the past 10k or so miles since replacement.
You've confirmed what I suspected you just needed to top off the system. It wasn't dry and killing your turbos but it was low and less effective.

Yes of course they bleed the system when they do the refill but as I've started a couple times now it isn't perfect and has been reported here a number of times that users have had to top off the system afterwards once all the air works itself out.
 

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Discussion Starter · #18 ·
You've confirmed what I suspected you just needed to top off the system. It wasn't dry and killing your turbos but it was low and less effective.

Yes of course they bleed the system when they do the refill but as I've started a couple times now it isn't perfect and has been reported here a number of times that users have had to top off the system afterwards once all the air works itself out.
If the intercooler isn't hooked up to the turbos and the turbos are instead hooked up to the engine coolant reservoir, why would they need to refill the intercooler when doing my turbo job?
 

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If the intercooler isn't hooked up to the turbos and the turbos are instead hooked up to the engine coolant reservoir, why would they need to refill the intercooler when doing my turbo job?
They remove the entire engine and subframe from the car to replace the turbos. Your air conditioning system is drained as well as coolant systems and they even change the oil all for that service. Your work order from your turbo replacement should have all of that listed.
 

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Turbo replacement includes a partial fluid refresh for the car,,interesting,,,
 
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