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Cleaning The Aac Valve On Rb25det Neo?

V28VX37

By V28VX37,
in Engines & Forced Induction

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V28VX37 Veteran

V28VX37

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Posted

Hi all,

I just tried cleaning the AAC valve on my R34 (RB25DET Neo) using these instructions: Diy Aac Valve Cleaning & Idle Reset., Auxillary Air Control Cleaning for RB25DET's

I didn't get far though before realising that the Neo AAC valve assembly is quite a bit different to the previous RB25DET's, some pics below. I started pulling out some of the clamps on the top right only to find out that there's coolant in there!

So I found a comment in this thread:

about the AAC-V. You may already know, but the NEO AAC-V is also the cold start valve, thats what the coolant lines are that run into it. so when you swap to the R33 AAC-V you may also need to get you hands on a R33 cold start valve, they are separate on the older RB25's.

Questions:

  1. What exactly are the three hoses going to the top right of the valve assembly?
  2. If I want to pull out the whole AAC-V assembly for cleaning how much coolant should I expect to come out of the cold start valve side?
  3. The internals seem different to the R33 AAC too. Do the solenoid etc. come apart for cleaning just the same though?

Thanks guys!

2659128420102364341S500x500Q85.jpg 2631685000102364341S500x500Q85.jpg 2987086470102364341S500x500Q85.jpg

89CAL Grand Master

89CAL

Posted
Posted (edited)

Pretty sure you can unbolt the AAC valve from that part you've pulled off. Looking at the last photo it looks like the valve is held in with 2 inhex screws. Or am I wrong? Can't see the AAC valve that well lol. But see if what I've said will work anyway

Those 3 hoses are to bleed air from the cooling system to btw. You crack the little bolt that's kinda in the middle of them all and run the car till all the air is out of the system (when you replace the coolant that is)

Edited by 89CAL
V28VX37 Veteran

V28VX37

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Pretty sure you can unbolt the AAC valve from that part you've pulled off. Looking at the last photo it looks like the valve is held in with 2 inhex screws. Or am I wrong? Can't see the AAC valve that well lol. But see if what I've said will work anyway

Thanks 89CAL, I might give that a go. It's pretty difficult to get to the valve though with those three hoses in the way.

Those 3 hoses are to bleed air from the cooling system to btw. You crack the little bolt that's kinda in the middle of them all and run the car till all the air is out of the system (when you replace the coolant that is)

Ok so it's probably not a good idea to pull them off?

I just want to clean the AAC valve, replacing coolant is too much work :rolleyes:

V28VX37 Veteran

V28VX37

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if you pull them off you'll have to top up the coolant and bleed the system afterwards. you shouldnt lose much coolant from there tho as its the highest point of the system
yeah you shouldnt lose to much, but if possible take the aac valve out of that section to save losing any coolant.

Thanks guys, I'll try pulling out the AAC valve only first and see how that goes.

QWK32 Veteran

QWK32

Posted
Posted (edited)

just pull the coolant hoses off, bugger all coolant comes out as its one of the highest parts of the engine, just the little bit thats in the lines is lost. when you put it back on just loosen the bleed screw on the valve to bleed the air out of the system, you have the engine running to do this.

the coolant lines are for the cold start valve, on the neo's it is apart of the idle control valve. the coolant is feed into the valve, as it warms up it heats up a wax pellet which expands depressing a plunger that covers the "T" shaped slit inside the valve. the air passing through that slit is what keeps your idle around 1100-1200 on cold starts.

apart from that the idle control solenoid is the same as the one in the that tutorial as far as cleaning it up goes.

Edited by QWK32
V28VX37 Veteran

V28VX37

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just pull the coolant hoses off, bugger all coolant comes out as its one of the highest parts of the engine, just the little bit thats in the lines is lost. when you put it back on just loosen the bleed screw on the valve to bleed the air out of the system, you have the engine running to do this.

the coolant lines are for the cold start valve, on the neo's it is apart of the idle control valve. the coolant is feed into the valve, as it warms up it heats up a wax pellet which expands depressing a plunger that covers the "T" shaped slit inside the valve. the air passing through that slit is what keeps your idle around 1100-1200 on cold starts.

apart from that the idle control solenoid is the same as the one in the that tutorial as far as cleaning it up goes.

Brilliant, thanks heaps for this QWK32! Should be a lot easier to clean the bloody thing once it's out of the car ;)

V28VX37 Veteran

V28VX37

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Here's a summary of the main differences between an RB25DET Neo and the original tutorial for series 1:

  • There are 4 bolts instead of 3 (doh :))
  • Wrap a towel around and under the three coolant hoses before loosening the hose clamps and pulling out the hoses. There's enough coolant coming out to soak half a tea towel. The coolant may be pressurised so wear eye protection.
  • As per the original tutorial I found it easier to disconnect the intake hose going to the base of the AAC at the other side of the head first, at the second hose clamp from where it branches off the main intake pipe.
  • My AAC assembly didn't have an O-ring between the assembly and the solenoid (step 9).
  • Take note of idle screw position before/whilst taking it out (number of rotations) unless you want to reset idle afterwards.
  • After putting everything back together remember to bleed the coolant system by loosening the bleed screw on top of the AAC assembly with the engine running until you get a couple of drops of coolant coming out.

Some photos below. I used cotton tips to clean the parts but be careful not to leave strands of cotton behind when cleaning.

Thanks again QWK32 for your help!

2857407520102364341S500x500Q85.jpg 2361142990102364341S500x500Q85.jpg 2940026230102364341S500x500Q85.jpg

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