VCP Cooling System Mod

[Wayne Presley]

I do a mod to bleed all the air the first time you fill it. what happens is there is an air pocket that gets trapped in the motor that would normally go uphill to the radiator in the WRX. In the 818 the water outlet goes down and traps the air. You put in a barb nipple in the water outlet and run it up to the degas tank. If you face the motor from the seating compartment, you drill and tap a 1/8 NPT hole at about 2 O'clock position in the water outlet. Run a line from there to the degas tank and fill as usual. All the air moves up to the degas tank and your overheating problems will be gone.

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod2_zps9688ed12.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod2_zps9688ed12.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod4_zps8b009e73.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod4_zps8b009e73.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod6_zps9877251c.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod6_zps9877251c.jpg.html)

Brass barb fitting
http://i213.photobucket.com/albums/cc175/vcpinjectionpb/P1020732_zpsb2367c3b.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/P1020732_zpsb2367c3b.jpg.html)

Hook to the left nipple on the degas tank
http://i213.photobucket.com/albums/cc175/vcpinjectionpb/P1020733_zps242bf98a.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/P1020733_zps242bf98a.jpg.html)

[Wayne Presley]

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod10_zps09ecaafa.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod10_zps09ecaafa.jpg.html)

[FFR-ADV]

Thank you Wayne!

[Harley818]

Followed this mod myself as have many others and I haven't had any issues. Thanks Wayne.

[CNC_Geek]

good thinking. I'll put that to good use. Looks like you have a SERIOUS tap handle.

[michael everson]

Just did this yesterday on a finished car with a chronic overheating problem. Problem solved.
Mike

[wallace18]

I have done this mod on both of my 818S builds. It is a must IMO. I have not had any cooling issues at all. With stock or aftermarket radiator.

[brian b 36]

i did it right at the begining of the build never had a over heat problum at all this should be in the build book for every one to do

[AZPete]

Same here. I did it and it worked perfectly. Sticky?

[Samiam1017]

where is everybody putting overflow tank? front? rear? or use 2 thx

[Hindsight]

I'm not even sure you need the front. The rear cap should be lower pressure than the front so if the system pressure gets high enough to require venting, all venting should be taken care of at the rear cap. I think Wayne at one point suggested just capping off the front cap so it doesn't suck air when the system is cooling down.

[Wayne Presley]

I cap the over flow port on the radiator, put a 1.3 Bar cap on the radiator, put a 1.1 bar cap on the degas tank and normal coolant recovery tank on it.

[Hindsight]

Thanks Wayne.... yeah when I said cap the front cap, I meant front port. I remember you saying you did this a while back and it made sense, and also saves space due to lack of front overflow tank.

[bbjones121]

So what exactly is everyone doing on the front side with this modification? Any photos?

[bbjones121]

Do you need two overflow tanks? Where does your right black hose off the expansion/degass tank go?

[STiPWRD]

I'm only using one overflow tank coming off the degas tank in the engine bay. I capped off the overflow nipple on the radiator. The small hose right under the degas tank cap (I think the one you're referring to on the right) is the one that goes to the overflow tank.

[Hindsight]

If you run two degas lines (one from the top of the engine and one from the radiator), you'll need a T to splice these two together and connect them to the medium sized barb on the degas tank.

[bbjones121]

I'm only using one overflow tank coming off the degas tank in the engine bay. I capped off the overflow nipple on the radiator. The small hose right under the degas tank cap (I think the one you're referring to on the right) is the one that goes to the overflow tank.

Where does your radiator cap vent go?

[bbjones121]

If you run two degas lines (one from the top of the engine and one from the radiator), you'll need a T to splice these two together and connect them to the medium sized barb on the degas tank.

This requires a line run up front.
So it sounds like there are two options:
1.) Run medium barb connection to a T which goes up front to overflow reservoir and radiator cap vent. Cap off front right hand side vent on radiator. Overflow res can be mounted front or back. One hose running along side of car. Perform Wayne's drill tap.

2.) Run medium barb from expansion tank to rear mounted overflow reservoir. Run radiator cap vent to front mounted overflow reservoir. Cap right side radiator vent. Perform Wayne's drill tap mod. No hose running along side of car.

Which is better?

[STiPWRD]

Where does your radiator cap vent go?
The nipple directly below the radiator cap is capped off, as I mentioned. There is also a coolant nipple on the top corner of the radiator that I also capped off.

Edit: My understanding of Wayne's mod is that it shifts the coolant connection on the degas tank from the top corner of the radiator to the top of the coolant cross-over pipe on the engine. I know some are running this configuration so that's what I'm planning to do. Here's some info from the 02 wrx FSM:
44175

[Hindsight]

This requires a line run up front.
So it sounds like there are two options:
1.) Run medium barb connection to a T which goes up front to overflow reservoir and radiator cap vent. Cap off front right hand side vent on radiator. Overflow res can be mounted front or back. One hose running along side of car. Perform Wayne's drill tap.

2.) Run medium barb from expansion tank to rear mounted overflow reservoir. Run radiator cap vent to front mounted overflow reservoir. Cap right side radiator vent. Perform Wayne's drill tap mod. No hose running along side of car.

Which is better?

Not quite.

Front barb on the radiator neck goes to an overflow only, not a degas. You either use a front overflow or you cap it and clamp it to ensure it doesn't leak.

Front barb on the side of the radiator that vents air can either be capped too, or can be routed back to the rear degas medium barb.

If you do Wayne's mod, you'll add the barb to the upper aluminum coolant pipe on the engine and route that to the degas medium barb.

If you do Wayne's mod AND run a hose from the radiator side fitting all the way back to the degas, you'll need a T to connect both these lines to the medium degas barb.

Large degas barb goes to turbo, small degas barb goes to rear overflow.

[bbjones121]

How can you just cap front radiator cap neck vent? If air is up front, it can't escape?

[Hindsight]

How can you just cap front radiator cap neck vent? If air is up front, it can't escape?

The cap neck vent isn't for air, it's for overflow. You don't need a front and a rear overflow really. The rear cap has a lower venting point than the front so if the system exceeds pressure, only the rear cap should be venting. The front cap should never vent. I suppose if something went REALLY wrong and the back cap couldn't keep up with the amount of overflow required (probably due to something very substantial like a head gasket failure), then and only then would the front cap need to vent.

If you are talking about needing to bleed air from the radiator, there is another barb on the side/top of the radiator for that. You can route that to the rear degas. If you cap it, you may need to check to see if there is air in the radiator by jacking the front of the car up and removing the radiator cap then topping off as needed.

[STiPWRD]

How can you just cap front radiator cap neck vent? If air is up front, it can't escape?
I added some info to my previous post. Since the coolant flows through the radiator top to bottom and there is no heat generation inside the radiator (only heat absorption by the air), there is no chance that you will get vapor bubbles that will need to be vented so it's ok if there's a small air bubble at the very top of the radiator, the coolant will still circulate.

[bbjones121]

Got it, thank you for the information. The original information in this thread doesn't really mention anything about the front end of the car. I am still a bit hesitant to block of the front rad cap vent, that was put there for a reason?

Nevermind...I think I just figured the answer to my own question...the front is designed to pull coolant in, the top/engine reservoir is designed to discharge. This way the subaru system is constantly purging any potential air/overpressure and filling from the lower point, i.e., the rad cap. right?

I know each is designed for overflow/expansion, but if there is air at the top of the front radiator, when that overpressures and vents, it will purge the air automatically. Given all the overheating issues this car is having, I didn't want to take any chances. I like the idea of tipping the car up to fill it though.

Anyways, I may just keep the stock overflow reservoir up front mounted where I have it and run the rad cap neck vent from the front radiator to this overflow and T off to go to the small barb on the expansion tank as it is in my 06 legacy. I heard from a coworker that the medium barb does not even exist on some older subaru models.

[Wayne Presley]

I only run the rear coolant overflow tank. If you run both, you run the risk of one tank being sucked dry and introducing air back in the system due to different height potentials. With one overflow tank, the expansion and subsequent draw back is controlled in one spot.

[GS guy]

Why not use the throttle body warm-up outlet already built into the water manifold for this purpose? On my engine it's located at the top/high point of the manifold just below the throttle body. Seems like a built-in solution for getting air out of the top of the engine?

[Hindsight]

I debated doing this, but I checked it with a laser level and the point at which it comes off the water manifold is not the highest point in the system. Right where Wayne taps the water manifold (where the hose goes on) is the highest point. Putting it on the throttle body outlet would still help prevent air lock when filling the system, and would provide some measure of automatic bleeding of air, but the best possible spot is right where Wayne does his.

[Chef818]

Is it necessary to put some type of sealant on the threads of the new barb you are putting in?

[Wayne Presley]

Is it necessary to put some type of sealant on the threads of the new barb you are putting in?

Yes, either teflon tape or blue loctite.

And you can shortcut your fill time by using a wet/dry shop vac. Put the hose on the barb fitting, use the vacuum on the hose while keeping the degas tank filled, apply vacuum until you get water out the hose and then the system will be 95% bled and will self bleed the rest in the first heat cycle.

[Chef818]

Thank you

[Chef818]

when you look inside the pipe you have screwed in the 1/8" NPT into, does it need to be flush or can it be screwed in further, so the threads of the NPT come out. Will that be fine or will the that give the air bubbles a place to gather around and not be flushed out the NPT nipple

[Wayne Presley]

when you look inside the pipe you have screwed in the 1/8" NPT into, does it need to be flush or can it be screwed in further, so the threads of the NPT come out. Will that be fine or will the that give the air bubbles a place to gather around and not be flushed out the NPT nipple

you can thread it in deeper

[2003wrx64]

Interestingly enough, the factory radiator on WRXs built til July 2002 had no cap on the radiator. It was only added later to ease burping of the system.

[GeoffH]

Does anyone have the pictures from the first few posts, or is there a trick to get photobucket to show them?

[Wayne Presley]

If you click on the pics, they will open on photobuckets site

[wirenut]

If you click on the pics, they will open on photobuckets site

They dont for me. Maybe just for you since they are your pics?

71236

[fastzrex]

Does anyone have the pictures from the first few posts, or is there a trick to get photobucket to show them?

The photos are actually stored at PhotoBucket and referenced here. PhotoBucket, at the first of July 2017, changed their policy of free referencing of photos to requiring a hefty subscription model. The photos can not be shown unless Wayne's upgrade's his PhotoBucket account at about $400/year.

I suspect Wayne will evetually get this done. Hopefully others can help (Wayne is very busy) and add the photos. I will soon also need this trick!

[frankc5r]

Photo bucket is full of garbage. Halt time it is so busy it hard to get a link. Reviews are terrible.

Save the headache and go to PostImage hosting- free and works great.

[wirenut]

I use Imgur. Works great for me.

[Wayne Presley]

The photos are actually stored at PhotoBucket and referenced here. PhotoBucket, at the first of July 2017, changed their policy of free referencing of photos to requiring a hefty subscription model. The photos can not be shown unless Wayne's upgrade's his PhotoBucket account at about $400/year.

I suspect Wayne will evetually get this done. Hopefully others can help (Wayne is very busy) and add the photos. I will soon also need this trick!

Oh GEEZ Photobucket....I have thousands of build pics on there because it was free. I'll have to move the pics when I get some time. Damn you Photobucket!

[fastzrex]

Oh GEEZ Photobucket....I have thousands of build pics on there because it was free. I'll have to move the pics when I get some time. Damn you Photobucket!

Exactly my feeling!

[Hindsight]

Wayne, try Imgur. Very easy to use and the pics load very fast.

[aquillen]

Wayne, given the info you've made available (and I've used my share of it already), I'd be glad to help repost. Need to work out mechanics of getting your images. I just retired and though still lots of irons in the fires I'd like to see your info back on the forum intact again. PM me if you like.

Over time most of the free sites hosting whatever (mostly pictures) go commercial - which is their plan from day one. Two or three of the remote computer/screen share tools have gone this route in the last 5 years - I've done remote access work since the late 90's and have had several nice tools suddenly go money-money-money. The 'freeness' draws in lots of users over time, then demand money, lose some users but come out ahead overall. In the end they all hope to get bought by 'soft or 'oogle and be billionaires overnight. Laugh at the users that get caught between the narrow rocks all the way to the bank. No way anyone here can afford $400 to host images for non-commercial use. Maybe if I was building a GTM...

They caught me too. And I was contemplating using it to build some family photo albums and print them there - nadda anymore. I switched over to www.cloudinary.com which is also free and runs the same risk. But looking the site over I decided it might last long enough. Uploading and getting links no more challenging that Photobucket was - maybe a bit simpler. Figuring out what picture got put where was a bit of job.

[Hobby Racer]

Wayne, try Imgur. Very easy to use and the pics load very fast.

Why not just use the image gallery on this site? Free hosting and you know it won't go away unless the whole forum does.

[aquillen]

Why not just use the image gallery on this site? Free hosting and you know it won't go away unless the whole forum does.

Good point. I need to revisit. Tried it early on and had troubles. Never came back to it.

[fastzrex]

Does anyone have a picture of this mod with the barbed fitting installed. I am working cooling system now and while I think I know how it goes, a picture would confirm it for me.

[Hindsight]

http://i.imgur.com/VU363sIh.jpg

[Harley818]

heres a link to my thread.... multiple pictures... post 76

http://thefactoryfiveforum.com/showthread.php?14763-Harley-s-818S/page2

[fastzrex]

Thanks, Hindsight, for confirming the location. I can now sleep!

[fastzrex]

heres a link to my thread.... multiple pictures... post 76

http://thefactoryfiveforum.com/showthread.php?14763-Harley-s-818S/page2

Thank you very much for the link to your build thread. I appreciate the help.

[chado skins]

Interestingly enough, the factory radiator on WRXs built til July 2002 had no cap on the radiator. It was only added later to ease burping of the system.

this is true. there are also aftermarket rads made for these years that have no caps so that they are drop in replacements. this type of sealed radiator would seem the best option for cleaning these lines up. then just run a single overflow off the coolant filler tank (which seems people are calling a degas tank?).

[grathke]

I do a mod to bleed all the air the first time you fill it. what happens is there is an air pocket that gets trapped in the motor that would normally go uphill to the radiator in the WRX. In the 818 the water outlet goes down and traps the air. You put in a barb nipple in the water outlet and run it up to the degas tank. If you face the motor from the seating compartment, you drill and tap a 1/8 NPT hole at about 2 O'clock position in the water outlet. Run a line from there to the degas tank and fill as usual. All the air moves up to the degas tank and your overheating problems will be gone.

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod2_zps9688ed12.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod2_zps9688ed12.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod4_zps8b009e73.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod4_zps8b009e73.jpg.html)

http://i213.photobucket.com/albums/cc175/vcpinjectionpb/coolmod/mod6_zps9877251c.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/coolmod/mod6_zps9877251c.jpg.html)

Brass barb fitting
http://i213.photobucket.com/albums/cc175/vcpinjectionpb/P1020732_zpsb2367c3b.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/P1020732_zpsb2367c3b.jpg.html)

Hook to the left nipple on the degas tank
http://i213.photobucket.com/albums/cc175/vcpinjectionpb/P1020733_zps242bf98a.jpg (http://s213.photobucket.com/user/vcpinjectionpb/media/P1020733_zps242bf98a.jpg.html)

I know it is 1/8" pipe thread, what size is the barbed portion?

[Scott Meyer]

We are getting close to reassembling our 2.5i NA motor and just wondering if this coolant mod is necessary? The instructions for the normally aspirated engine shows installing a fill port of the coolant line in the engine bay where a high point is created for burping coolant and filling.

[fletch]

I’m guessing here because I don’t know the arrangement of the NA system. I think you’ll still want to do this mod. It ends up being a high point in the system and air gets stuck here.

The mod was pretty easy to do. I left the crossover pipe on the engine and did it. Just stuff a rag inside past the place you’ll drill and tap. Then vacuum it out when done. :cool:

[RPGs818SNA]

The rev 1V manual says: If using a Naturally Aspirated engine, there is no rear overflow tank. It is recommended that a fill kit is used such as Peak PKF0AA.

I think what they mean is that there is no pressurized degas tank on an NA engine, only a vented overflow tank normally beside the radiator. I think the manual is trying to help solve the air bubble problem with a fill kit, but it’s an awkward solution.

I implemented a smaller manual version of Wayne’s Mod by threading a #8-32 hole in the aluminum casting where it’s pretty thick and filing the top flat. I cut a slot in the bottom of an aluminum screw so I can vent the air bubble when it’s hot. A washer and O-ring keep it sealed otherwise. I’ll also mount the donor expansion tank and run the overflow line as the manual shows. It’s a manual process and messier than Wayne’s, but I think it will work. Once the air bubble is released using the vent, and perhaps periodically thereafter, I think the coolant should remain air free, but I can’t vouch for it until it’s tested.

137461

[hartwellguy]

Here's another method for air venting of the upper radiator hose. I used a barbed bulkhead fitting and cut off the non-threaded side, punched a hole in the radiator hose, and inserted the fitting into the hose with washer and nut. My engine was already in the car and I thought this might be easier than drilling and tapping the aluminum. I hope it works! It's these little details that make me wonder what other problems I'm going to run into that are addressed on the forum but which I haven't found out about yet....
140170140169140171140172140173

[hartwellguy]

This is how I filled my system with coolant. My donor is an '06 WRX turbo which came with an aftermarket radiator with a traditional cap on the top tank. I located the overflow tank in the front of the car and ran a 1/4" line from the purge tank on the engine to the overflow tank, and teed this line to another line from the overflow on the radiator, so that overflow from either the radiator or from the purge tank will go into the overflow tank. To fill the system, I first filled as much as I could through the purge tank and through the radiator cap. Then I filled the overflow tank with coolant and applied air pressure to the tank through the vent fitting in the yellow cap, which pressurizes the tank and forces coolant into either the radiator or the purge tank (with the radiator cap ON, purge tank cap OFF). Initially, all the coolant goes to the purge tank since it is open to atmosphere, which fills the 1/4" line running to the tank. Once filled, I clamped off this section of the vent line, so that now coolant only flows into the radiator. The radiator cap acts as a check valve to keep the coolant from running back out. When the coolant gets low in the overflow tank, you stop and refill and repeat the process (several times!) until fluid begins to run out of the purge tank. Let it settle and repeat again until the purge tank remains full. Seems like this eliminated almost all of the air in the system. Won't know for sure until I can crank 'er up, which is going to be a while.
140174

[DJWalker]

If this mod is done, what happens to the hose that would otherwise be attached to the left barb on the degas tank? The manual says that comes from the barb on the top right of the radiator.

[driveslikejehu]

Not exactly sure what the question is, but this may help.
On my set up, 1A (marked on degass tank) originally went to the top of the radiator - not overflow. It now goes to the nipple on the aluminum coolant manifold on the engine- the VCP MOD. The other degass input (1B) goes/comes from the engine coolant manifold- in my case near the turbo.
176311 176312

Filling was really straight forward. Just filled what I could at the radiator and degass tank. Then used this fill gadget, got it running and filled it as needed.

176313

Let me know of another pic would help...

[DJWalker]

Thanks @driveslikejehu, what I don’t understand is what happens at the radiator end. You said “…originally went to the top of the radiator - not overflow” does that connection get capped or something once the mod is applied?

[driveslikejehu]

Thanks @driveslikejehu, what I don’t understand is what happens at the radiator end. You said “…originally went to the top of the radiator - not overflow” does that connection get capped or something once the mod is applied?

Yes, it gets capped. That's what my 2nd pic shows, maybe not clearly... My port labeled 1A on the degas tank originally was connected to the one labeled 1A on the radiator.

[Ajzride]

I used a tee and tied the radiator and Wayne’s mod into the same degas port. That line between the radiator and the degas tank really helps get air out of the system.

[DJWalker]

Yes, it gets capped. That's what my 2nd pic shows, maybe not clearly... My port labeled 1A on the degas tank originally was connected to the one labeled 1A on the radiator.

Sorry, driveslikejehu, for some silly reason I had missed your 2nd photo. That shows exactly what I wanted to know and very clearly!


I used a tee and tied the radiator and Wayne’s mod into the same degas port. That line between the radiator and the degas tank really helps get air out of the system.

… and that was the other possibility I was thinking of. Thank you.

[Ajzride]

If you run a line from the radiator to the degas tank, you need a "zero psi" radiator cap. Basically a cap with no spring in it so that the radiator doesn't build pressure, that needs to happen at the degas tank.