I have finished the Suby conversion in a Bay window and driven it-awesome.I am trying to understand how the cooling system works.Having some issues.I don't understand how the thermostat is located on the bottom hose - by the time it opens,the engine and radiator are really hot.I have a stainless pipe connecting the radiator bottom outlet to the thermostat housing that's about 1500mm long.I have read somewhere that the two 16mm heater pipes must never be restricted,or it can overheat.I have fitted a universal type heater unit behind the drivers seat and thinking maybe that the hoses are too long for the water to circulate correctly.I have used a late Commodore heater tap which always keeps the circuit open for flow.It's got me stumped.

Can you draw a diagram of your cooling system? Where is you radiator located? Do you have a temperature gauge?

karmann-I have a couple of pics.The radiator is fully sealed to the body and I have cut the spare wheel holder out and fully sealed that -so all air coming thru the top vent has to go thru the radiator.I have a 12inch pushing fan in a shroud against the radiator on a thermostat.I have just fitted a good quality guage to it-I think the cheap one the owner had in there was no where near correct.I am trying to understand the original Subaru concept where the engine,complete radiator and bottom hose have to get to 75C before the system can flow to start cooling.

Your setup looks pretty good and as you say the heater circuit has constant flow - length shouldn't be a problem.
A few more questions:
1. Where is your exhaust/muffler located?
2. Does your fan come on when driving on the highway and at what temp does it come on?
3. Is the thermostat good? genuine or aftermarket?
4. Do you have a scoop on the intake vent?
5. How restrictive is the fan on the other side of the radiator ? - not the best setup as a push instead of a pull.

Karmann - you got me thinking about the muffler position - the exhaust bloke had it about 50mm away from the lower pipe to the thermostat housing. I made a new system today with a smaller muffler coming straight out behind rh back wheel. Will road test tomorrow.its a new thermostat I got from eBay. I tested it in a saucepan-starts to open at 70 and fully open at 83.Owner has ordered some plastic scoops that clip to the top intake vents

Hi

Your right cant restrict the heater circuit in any way, mine is just in a loop. you could try running a 4 way tap from a V6 commodore. lots of good info on this site vwkd.com

Steve

Good day - yes am running a Commie heater tap.Went for a run this morning with the exhaust now out behind the RHR wheel.Nothing changed.Getting to 105 on the guage.Checked with my Digi thermo - same reading.Thinking maybe the 12inch plastic fan is not doing it's job on the pushing side.Got an OG Suby fan and will fab some brackets to have it on the pulling side. Run it just sitting on the rad-boy does it pull some air.Get some paper near the rad and it's sucked straight onto the face.

Not sure if you've had a look at this post.

https://forums.aussieveedubbers.com/viewtopic.php?tid=95862 

I think you're on the right track. My best bet is you have restricted air flow or not enough through your radiator. Also move as many other heat sources out of the engine bay - namely exhaust/muffler.

You could try just running it with the heater circuit in a loop

Is there any reason why I can't take the alloy cap off the injectors where the wire connector goes - and turn the injector thru 180 degrees and refit the cap.This gives me heaps more room for the fan shroud to clear the wire connector.Thanks karmann-thats a good read.I am starting to think this thing may have a head gasket issue.

karmann-I have now fitted the OG Suby fan(the bigger of the two) with it's shroud on the engine side of the radiator.Boy does it pull some air now.On a test on the highway,the temp still got up to 105,so i bought it back home.When i turned around after about 5 minutes checking things with it idling,the temp went down to 85 and then I gave it heaps(was doing 130 for a fair stretch) before it started to creep up again.When I got back into town and doing 60,it shot up to 105 again.You asked me if I had a Suby thermostat?Will it make any difference.I got a new one from ebay.It's doing the right things as far as temp goes.

My opinion is that the radiator in its present position just wont cut it . Is another radiator on the opposite side a option. My brothers baja bus with a modest radiator up front has never gone over 98-99 even under soft sand load. Mind you he will be looking at get more cooling with a bit bigger 3 core radiator. I'm looking at the twin rear radiators for my bus but will have holes in engine lid to allow as much heat out as possible. A thermo on each side with one on ecu trigger and other manual switch. I'm not 100% sure this is even really enough as we have Baja buses that are used on the beach so soft sand at times.

I won't get into the debate as to whether the radiator will work in that position because it can and does but has to have everything set up correctly.
Somethings definitely not right - you did suspect a head gasket? These engines are almost 30 yrs old now and many have done a lot of kms and still have original belts and water pumps and galleries full of shit.

At this time of the year it should be running very cool. As an example driving some almost 500km from Brisbane to Nambucca with a full load of camping gear and a trailer, my radiator fans only came on once when sitting in traffic in Coffs Harbour. A friend has a Mk1 Golf radiator in the same position as yours and tows a race car in the heat of summer in central Qld with no issues.

I would be looking for issues with the motor more closely as the erratic temperature doesn't quite make sense.
I have an LED on the dash that lights up whenever the fans kick in - will only run for about 30 secs at a time in stop start traffic until moving fast enough.
If the motor has issues it will overheat with a front mounted radiator - that's where I would focus my attention.

Thanks karmann.Waiting on some of the plastic scoops for the air vents.Still running fresh water in the cooling system-will add coolant and see if any signs begin of coolant going elsewhere.The fan relocation has stopped the thing boiling at speed - used to get to 120 quickly and overflow the bottle.

Another thought-are these things prone to water pump impeller corrosion if they sit around without any coolant?

Hi, havnt read it all thru...but I didnt like where the thermo was so i put it after the engine not before...cold water wont open the thermo...an alternative is to drill a big hole in the thermo...

The way it works has got me beat.I had it running in the shed yesterday for a long time.The top hose got that hot I couldn't touch it-but bottom hose was stone cold.Temp guage was up over 90C.After a while I noticed the thermostat housing was just starting to feel warm.A long time later it gradually got hotter then finally it opened and the bottom hose got hot.It has something to do with the 2 heater pipes and that circuit.I remember reading that that circuit must always remain open or it will boil.

As you probably know its critical to bleed the system. Had a similar problem on a EJ22 recently after a water pump change. Never been a issue before. I bled system 3 times and still not perfect so put a filler/bleeder on the heater loop to speed up the process and be 100% sure heater loop had no air (very important). Sorted the problem. Check for air locks 3 times before you start pulling heads off.

If you speak to most mechanics they will tell you that Subaru motors are an issue to bleed.

Drill a small home in the top of the thermostat.

I have always done this on my car and it works a treat.

I also have a bleed line that runs from the engine out pipe back to the fill pot and also a bleed valve on the top of the radiator.

So where is the air being trapped?Would drill and tap a eighth NPT thread into the alloy water pipe on top of the motor-then fit a needle valve with a length of hose to radiator height?Have it open when filling the system.

I used a vacuum bleeder the last time I filled my system, it works very well. Ive always been able to fill my system and have it grab some more coolant when needed from the overflow bottle, it only takes few warm up and cool downs to do it

OK-bit of an update.I am thinking you blokes may be onto it.The second last time I drove this thing,the temp was up nearly to 120,so bought it back home.The water bottle didn't increase by much(maybe 5mm ) and it was very hot.Next morning the bottle was completely empty.I suspected that it was using the water through the head gasket,because there was no other signs.On the last run,it got to 98 for a very short time then settled on 94 for the rest of the run.When I got back into town and running at 50KPH,it dropped down to 82 and stayed there.Bottle had grown about 15mm and was back on cold fill level next morning.So I am guessing that the thing must have been full of air,which it had expelled.Will run it again when the air vents arrive.I have made an 80mm deflector that I TEK screwed to the back chassis rail underneath,and will probably tape up the air vent on the drivers side,to prevent any undue pressure on the air coming in the LH side.

When I do a van I pour water over the block and heads, just enought to fill most of the valleys. Then I run it up to temperature, if the water on the block/heads starts to boil I shut it down and let it cool. I keep doing this cycle until I get to the point where the water is not boiling off, steaming is ok but not boiling. This way you can avoid overheat the engine.

I use a garden pressure sprayer to pressurise the system and bleed off any air, easier on a T3 as they have a bleeder on the radiator.

Yes the heater circuit must flow at all times as that water goes back to the thermostat, if you overcool the heater water you can get the engine to overheat as a result(problem in the North American vans with dual heaters)

Back to the drawing board.Went out yesterday with the new wind deflectors,the ally wind defector I put under it at the rear chassis rail and it went up to 110 almost straight away.Had to pull over to let it cool.Took off the side vent deflector-no change.When home i checked the temps with the gun-everything up in 90's.Took the engine covers off,and the water pump pulley was red hot-couldn't touch it.Only showed 78 on the gauge.Water bottle was about 25mm above low mark,and is back on low mark today.Took water pump off today-looks brand new.Its a GMB brand-don't know if that's genuine Suby.Did find I believe that the timing on the LH camshaft is one tooth out. Don't know how critical it is.With the water bottle doing what it is-I reckon there can't be air in it or it would pull more water back in when cooling.

Buy a "genuine" water pump. Google it and you will see the difference. Also get rid of your heater tap setup temporarily and just short loop heater pipes. Make sure no kinks. Bleed and go again. I think its still air lock.
Let us know.

Well Bone and Karmann - reckon you were both on the money.I had an issue with the positioning of the Suby cooling fan obstructing No4 spark plug hole.So pulled it all to pieces and flipped the fan shroud over so the mounting rib in the way would be at the top.Worked a treat.Had to cut a small relief in the shroud to clear the cam cover.I filled the radiator again(must be the 10th time I have had to do it) and got it running.I decided to try bleeding it.Because I have a throttle body reverser,it is now very high on the motor.One of the small hoses that goes to the TB base is easy to get at-so while it was running I took the hose off-well I haven't seen so much air come from anything-air was even in the water stream when it came out for a while then ran clear water.Closed everything up,topped up the rad and went for a cruise.Did about 50ks out and back and didn't get over 86C - now too cold.I also cut the small bleed ball from the thermostat and drilled the hole out to 6mm.Will put another one in then do the coolant. No 4 spark plug lead is too close to the fan blade-even if I cable tie it back.Went to Repco and got a set of leads for a Hyundi - they have right angle ends.Fitted the small rubber flap from a Type 1 spark plug lead to keep rubbish falling in the hole.Works real good.Can't believe how different the motor sounds now with the cam timing correct. Thanks for your help fellas.

That's excellent - they are a brilliant motor. The fan should only come on now in stop start traffic. It's a good alternative location for the radiator/s, nicely hidden and out of harms way. I have on occasions in winter taken off my air scoops if running too cool however it's doesn't get that cold up here in Qld.
Well done.