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Subaru H6 conversion, cooling system problem
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MartinJS
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PostPosted: Sat Sep 25, 2021 4:44 pm    Post subject: Subaru H6 conversion, cooling system problem Reply with quote

Hi all,

1988 2wd conversion to a Subaru EZ36. Engine installed, up and running.

I knew the cooling system on the van is a sore spot so I did a lot of research on this and other sites and, combining as much info as I could, designed and installed the cooling system. New water pump, new thermostat (installed with parts diagram in front of me so in correct orientation), new radiator (one of the good Hella's I came across), all new SS pipes and all new rubber hoses.

The layout of the system is: engine outlet straight to radiator, hoses correct orientation, return line from radiator to thermostat housing with t-line to upper expansion tank inlet. Heater outlet straight to heater, heater return line to engine heater return with t-line into lower expansion inlet. There is a small pipe from the heater outlets on top of the engine directly to the thermostat housing and the heater return line goes to the thermostat housing too (both to open the thermostat as engine warms).

Recently filled with coolant and bled. I did first start of the engine a couple of days ago and got no coolant flow at all. Hoses cool, expansion tank cool, no flow from radiator bleed, heater cold. Did some more bleeding, tilted van front and back, got a fair bit more coolant in (half a gallon), but still no flow.
Did some research on bleeding techniques and today, using old expansion cap, pressurized the system to about 12-15psi. Was able to get flow from radiator bleed and added about 3/4 of a gallon more coolant (now about 5 gal in system total). With engine run, expansion tank gets warm/hot, hoses get warm but only about 2-3 feet from origins at engine, no heat but there is coolant up to the heater. Engine has been through heat cool cycle about three times since pressure bleed, no room to add more coolant in the expansion tank. No significant engine cooling, can run it roughly the same amount of time to reach about 105-110 degrees before shut off each time.

I'm at a bit of a loss now. Can anyone see a problem with the circuit design? I thought I'd done my homework and the system should work but did I miss something? Any tips to bleeding the system better? I guess if no one has any ideas, my next step is to test the thermostat but I'm dreading it because of draining all the antifreeze and re-filling (tips appreciated). It's a new Subaru thermostat which is definitely in the correct orientation but I just didn't think to test it before installation.

Any tips or advise would be greatly appreciated.

Thanks in advance,

Martin
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MartinJS
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PostPosted: Sat Sep 25, 2021 5:01 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Sorry, got the bypass part of the circuit wrong: heater line from engine teed to lower inlet on expansion, return line from radiator teed to upper inlet in expansion. I said the heater return went to the expansion.
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MartinJS
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PostPosted: Sat Sep 25, 2021 7:09 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Sorry, also realized I posted the temperature in Celcius. So the 110 I've seen is 230F. Should be seeing flow...
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Captain Pike
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PostPosted: Sat Sep 25, 2021 7:13 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Photos help. Also a diagram of how you routed the rad.
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MartinJS
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PostPosted: Sat Sep 25, 2021 8:01 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Have a diagram as a pdf but can't figure how to post it.. Sad
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PostPosted: Sat Sep 25, 2021 8:15 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Took a picture and posted the pic!

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Captain Pike
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PostPosted: Sun Sep 26, 2021 7:10 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

https://groups.io/g/SubaruVanagon/files/Cooling%20...system.pdf
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9.5isCanadian
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PostPosted: Sun Sep 26, 2021 2:58 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Sorry no help on the cooling topic but damn I want to do this swap in my lowered 81 sunroof van.

I’m from the generation of “no replacement for displacement.”

Not to derail but any pictures or a build thread?

Cool

Owen
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PostPosted: Sun Sep 26, 2021 3:57 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

The feed to the rad should not go in the base of the rad. That configuration forces the pump to push coolant into the rad rather than a "drain" back to the engine(thermostat).
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Crankey
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PostPosted: Sun Sep 26, 2021 6:03 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Captain Pike wrote:
The feed to the rad should not go in the base of the rad. That configuration forces the pump to push coolant into the rad rather than a "drain" back to the engine(thermostat).


Dang I had never thought about that, easier for the pump to pull it through the engine too ?
Is this how all engines are plumbed (main radiator lines) in the vanagon ? I haven't looked at any of this in 6 years.


What about the throttle body coolant line ? Or de-ice line ?
I don't see the oil cooler plumbed into the system either.
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MartinJS
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PostPosted: Wed Sep 29, 2021 4:43 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Sorry about the delay, lots of head scratching and head against wall banging. The way I had the coolant routed just didn't work. As noted, there are coolant returns directly to the thermostat via the throttle body and the oil cooler (my diagram is just too crude to show them). I thought they would be enough feedback to the thermostat to make the system work. Not quite. Worked a couple of times, didn't work most of the time with no thermostat opening resulting in overheating.

So, today, I re-routed the coolant so the return from the expansion tank went to the heater return line instead of the radiator return line. Major blue shower and about a gallon on the garage floor. Oh well. Increased feedback to the thermostat did the trick and now the system works as it should. Lot's of heat from heater, peak engine temps closer to 97 Celsius instead of 105-110 and generally seems to work as it should.

Thanks everyone for the feedback, all made me think about what was happening and made me realize what I was doing needed to change.

Cheers,

Martin
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Captain Pike
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PostPosted: Wed Sep 29, 2021 7:01 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Applause Applause
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.....................All Current.......................
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PostPosted: Thu Sep 30, 2021 7:25 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

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PostPosted: Thu Sep 30, 2021 7:27 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Previous post is a pic of the new cooling system layout I'm using for the Subaru EZ36 transplant into my '88 Westfalia. Works well so far. I'll post again if there are any issues or more modifications needed.

Thanks,

Martin
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harvgwen
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PostPosted: Thu Sep 30, 2021 9:29 pm    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Captain Pike, I’m certainly no expert on this but I think the flow to and from the radiator is correct. I think VW wants the coolant pushed up through the radiator from the bottom to aid in bleeding out the air.
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PostPosted: Fri Oct 01, 2021 4:27 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

harvgwen wrote:
Captain Pike, I’m certainly no expert on this but I think the flow to and from the radiator is correct. I think VW wants the coolant pushed up through the radiator from the bottom to aid in bleeding out the air.

Take a rad apart then repost. Rolling Eyes
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PostPosted: Fri Oct 01, 2021 4:35 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Captain Pike wrote:
harvgwen wrote:
Captain Pike, I’m certainly no expert on this but I think the flow to and from the radiator is correct. I think VW wants the coolant pushed up through the radiator from the bottom to aid in bleeding out the air.

Take a rad apart then repost. Rolling Eyes


A thread of mine from 2015. I pulled the plastic side tanks off……

djkeev wrote:
Over the weekend I installed my new radiator because we all read how horribly clogged they are after 30 years...... Right?

Well, on a lark today I peeled the tanks off the core to see my 29 years of gunk......

NO GUNK!!!!!

Discoloration, yes!
A little bit of debris, yes!
Clogging? No!

Ah well, better to be sure that I am good rather than to wonder.......

Dark is the lower tank/core
Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Tanks..... Light color is Feed chamber to the top 1/2 of the core.....

Image may have been reduced in size. Click image to view fullscreen.


Dave


Notice the radiator is broken into two chambers.
Upper 1/2 is Hot coolant flowing right to left
Once it gets to the left it drops down to the lower 1/2 and flows to the exit on the right.
Rough drawing of flow, looking at fan side of radiator …. The left tank is open top to bottom.
The right tank is broken into two chambers

Image may have been reduced in size. Click image to view fullscreen.


Dave
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert


Last edited by djkeev on Fri Oct 01, 2021 4:56 am; edited 1 time in total
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PostPosted: Fri Oct 01, 2021 4:54 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Thats the old style. however it still drains out the bottom. Check with any vendor who sells the SS pipes to confirm. Pretty sure they know how to install them.
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If You Build It______It Will Run
1959 Panel bus, 1966 Single cab. 73' 181. 73 Westy. 91' H6 Vanagon 3.3L.
.....................All Current.......................


Last edited by Captain Pike on Fri Oct 01, 2021 4:57 am; edited 1 time in total
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djkeev
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PostPosted: Fri Oct 01, 2021 4:57 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

Captain Pike wrote:
Thats the old style.


1986 original

How does the new style differ?
When did the new style begin?
Is the new style only found in replacement radiators?
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert
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Captain Pike
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PostPosted: Fri Oct 01, 2021 4:59 am    Post subject: Re: Subaru H6 conversion, cooling system problem Reply with quote

As long as you dont overheat in 95* weather in traffic who gives a shit?
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.....................All Current.......................
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