Header Tank Internal Corrosion, Version 7 STI.

I brought this GDB header tank for my single turbo conversion:

Looking rather dull and oxidized:

I opened it up to clean it up ready for paint and found this:

I guess it's either never had antifreeze or has been sitting empty for a while.

15 minutes soaking in Aluminium Brightener, (sulphuric acid):

The lid got a good wire brushing, the pitting is so deep it's almost right through:

All ready for a lick of paint:

2 coats of VHT SP124 gloss black engine enamel:

I've ordered a can of VHT aluminium SP127 to paint the tank base, instead of trying to polish it up. It should end up near identical to the manifold.

This restored header tank has lasted 11,500km, but is now seeping coolant from the rear of the lid.

I can't find the part number for a new lid gasket/o-ring, according to the threads I've read so far Subaru only sell the tank as a complete unit. So rather than buying second hand again or trying to fix it with silicone, I'm looking at the later model plastic tank for $95.75 delivered through partsouq:

Has anyone seen a part number, or brought the alloy tanks gasket/o-ring? Or know the specific part number for the version 7 alloy tank? 21132AA130?

https://partsouq.com/en/search/search?q=21132aa074

From what I've seen 21132AA074/21132AA075 are the older alloy tank. Here's my original BE/BH/V5/V6:

Also a difference at the bottom coolant hose, version 7 on top and BE/BH/V5/V6 on the bottom:

You can make o-rings up in any size you like, just need the material and some superglue.

I used to do it all the time at work, for random water cooling passages in plastic injection dies.

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You can make o-rings up in any size you like, just need the material and some superglue.

I used to do it all the time at work, for random water cooling passages in plastic injection dies.

An adhesive gasket silicone or three bond would be my choice if I was going for a temp fix.

I've ordered the new plastic header tank 21132AA131, also a new GDA/GDB header tank bottom hose 21204AA691:

Along with GDA/GDB turbo coolant feed hose (head-turbo) 99078AA450:

I've seen a few threads claiming a noticeable difference in intake manifold runner temps between the left and right banks/cylinders 1-3 and header tank mounts. When changing from the alloy to the plastic tank. Makes sense when looking at the thermal conductivity between the two materials, 210-0.25:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Taken from this thread where someone fitted some phenolic washers under their alloy tank:

http://www.subaruforester.org/vbulletin/f87/expansion-tank-isolation-12047/

Might get the IR temp gun out and see what sort of differences I get before and after.

Really good documentation here, thanks for the continued contribution

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Really good documentation here, thanks for the continued contribution

Cool, thanks Kamineko.

The new OEM bits arrived today, cheers again partsouq:

J2 as well ross how much thro partsouq?

Do that intake runner heat test if poss and add results in that impeccable manner of yours.

 evowrx said:

J2 as well ross how much thro partsouq?

Do that intake runner heat test if poss and add results in that impeccable manner of yours.

Nah, just a spare that popped up on trademe. Definitely will, been monitoring temps for the last week.

Dont even need to ask do i ross youre a bloody asset to the club.

Nice, thanks Clint.

99078AA450, will that suit my V5/6 turbo water return?

Or is it something else?

Depends which coolant hard line is on the back of the head. My head coolant hard line is from a version 7 GDA/GDB.

Bottom 12mm GDA/GDB - Top 10mm BE/BH secondary:

Looking at a VF30 it has the same coolant pipe under the CHRA as the VF36, this is 99078AA450 fitted on my VF36:

From the bottom of page 2:

http://clubsub.org.nz/forum/showthread.php?43004-Rosssub-s-Single-Turbo-Conversion/page2

I think this is the hose for Version 5/6 with VF28 21144AA020:

Fitted:

Part listing on ICP:

http://japanesecarimports.net/parts-info?id=5026&cat=96&sub=97&sec=144&var=31&dc=0&gen=&searchKey=&searchPart=

Thanks encyclopedia ross. Once again a wealth of knowledge.

Hmm I've changed the turbo, I'm actually going to be running a TD05 16G which makes things a little interesting. I believe that the water return is in a similar position but the oil line might foul on the wastegate actuator. I wish I could have the car and all my bits on hand. Would make acquiring parts way easier.

Sweet, yeah definitely easier with it all laid out in front of you. The OEM oil feed lines are bendable if your careful. That's my original VF27 secondary oil line used in the pics above.

The new header tank went in today. To save draining the coolant completely I used a turkey baster to empty the original alloy tank, saving the coolant to reuse. Then removed the 3 top hoses:

Then unbolted the header tank and removed the bottom hose:

Original tank removed, beside the newer plastic tank:

Not that much smaller when you take the alloy tanks lid out of the picture:

New bottom hose installed, new header tank bolted to the manifold and top hoses back on:

Coolant back in and a precautionary air bleed. Then some before and after shots:

The outside of the plastic tank sits a minimum of 10'c cooler than the alloy tank, also radiates a lot less heat. Alloy tank averaging 85'c at normal operating temps, the plastic tank 75'c.

With a noticeable drop of 5-8'c in the intake manifold runners at the tanks mounting points. So more even temps now between the left and right bank runners. Also less stationary heat soak into the MAF housing and intake pipework.

Thats fairly impressive!