Subaru swap coolant system drawing wanted

[david2676]

Now that its warming up I thought I would revisit this and see if I could find a solution. Last summer when traveling thru Mexico my temps began to climb when after running down the freeway for a period of time when we exited and came to a stop or slow traffic The temp would climb quickly to 220, most of the time the Fan would not come on. never boiled over but the high temps were concerning. I have since replaced the gauge sender , water pump to a cast.high flow , OEM Subaru thermostat. I thought my troubles were over but the other day when it was 100 degrees out I noticed the Van spike a bit ...not to 220 but to close to 200.

The last thing to consider I think is the routing of my coolant lines, I am using a plumbing given to me by the motor builder he routes his heater line different then others I have seen to provide better cabin heat. What is the preferred routing or best case routing ? can someone share a link or a drawing ?
_________________
64 bug
91 Vanagon/ Subaru swap Westfalia

[Hammy1]

Are you sure it’s actually a temp issue and not your coolant tank low coolant sensor turning on? Your fan is controlled by a sensor in the rad that turns on the fan at high temps. If your fan isn’t turning on that means your temps are fine. It could have some air in the system? When the coolant is low the needle will peg and the light flashes. This happens right away.
Jon.

Jon

[Paulbeard]

This is probably completely on the wrong track but if you are using any of the cooling system artifacts, like the OG pressure cap, maybe test to see if it's working. I had a recent episode of overheating as a result of one of those (mine was made in W Germany? Yikes…) being dead. My temp gauge never moved past the middle (normal) mark yet the pressure tank and overflow were both boiling.
_________________
Currently -> Frida: 87 Tizian Red (mostly) Vanagon GL Westfalia w/ 2.0L ABA conversion
Formerly -> Steward of a 73 Super Beetle (Beater) and 67 Beetle 1300 (Little Max) both names by POs

[davevickery]

This is Tom Shiels Coolant 4 design. It is similar to the way a lot of people do it, whether you use the extra thermostat housing port or not. My coolant temps stay very steady and basically uses a simplified version of this. I made a modified drawing of the way mine is and posted it a few posts down.

When looking at this picture, you don't need that thermostat housing port. Instead the coolant hose coming off the left side of the manifold tees back into the 1/2" metal coolant return pipe that is up near the firewall on passenger side of the engine.

The bleeder valve shown to the left of the coolant tank is also not necessary (just makes initial filling easier but I've never found it that hard anyway). This design does require that your rear heater valve remain open so any air will bleed into the expansion tank. Or add a bipass (connecting the heater lines so there is always at least some flow through the expansion tank. [Without some continous flow through the expansion tank, you can develop small amounts of air in the system from loose hose clamps or whatever and that can cause the water pump to cavitate and you get intermittent hot temps and hot spots in the engine].

I think the Bipass Air Valve shown is only on certain engines (not my 2.5) and so when you remove all the extra crap, this design is simple and easy to understand.

[wesitarz]

A diagram of your cooling system would be helpful. I have a Smallcar dedicated bypass from the coolant manifold to the t'stat. My expansion tank is in the heater circuit and I had never noticed a spiking temp similar what you describe until I put in an aftermarket VDO temp sender and gauge. Temp would spike in stop and go traffic and did not show on the VW gauge.Temp would come down with the heater on. Turned out I needed a bypass in the heater circuit 3/8" brass/ 1/2" hose.

[11BC2]

OP:

What Subaru engine are you using? Phase 1 or Phase 2?
How many miles are on the engine?
What work was done to the engine before installation?

I ask, because if you were driving a Subaru, this is a classic symptom of failed head gaskets.

[wesitarz]

If you google subaruvanagon cooling system image you will get some diagrams. This is the one that I have with the expansion tank in the heater circuit. With a VDO sender inline just off the coolant manifold I started seeing temp spikes as you describe. My rad was new and I replaced the expansion tank cap,water pump and t'stat. With the heater off (front only for me) I realized that the expansion tank was cut off and there was no flow from that end of the coolant manifold. I got away with it for years because my heater shut off valve did not fully close,but when I fixed the cable to the valve it became a problem. Adding a bypass between the heater lines (mine is near the gas tank) solved my temp spike issue. My VW temp gauge has a 33 ohm resistor inline, so maybe isn't as sensitive as the VDO.

[wcdennis]

I would propose that you actually don't have a problem since you ave pushed your system to extremes and it has never boiled over. I think what you are seeing as a problem, is caused by the long trip the coolant makes from the engine to the radiator. After a long hard run, the system takes a while to settle to the new idle state. The reason the fan doesn't come on is because the gauge sensor is on the engine and the fan switch is on the radiator. You could rewire your system so the Subaru ECU controls the radiator fan. That would give you some piece of mind, hearing the radiator fan running when the temp sensor rises. It might help bring the temps down more quickly, but I suspect they will still rise in the conditions you describe.

[davevickery]

[davevickery]

[davevickery]

Here is a diagram of my coolant routing which is similar to Toms Coolant 4 diagram I posted at the top but I removed all the extra bits I am not using. And it works great.

The heater bipass is shown in the picture up near the heater, but on the van is a lot closer to the engine. And the 1/2" hose off the small side of the coolant manifold looks like it goes down and tees in right by the thermostat (which it could) but instead it goes up and tees in just before where the heater return line connects with the 1/2" metal coolant pipe that goes up and over the engine. It is more protected and a shorter hose going that way.

[Jake de Villiers]

I've been running Tom's Concept #4 for ~75,000 miles with no issues. I didn't reverse the coolant manifold but I am using Tom's thermostat housing.

Good heat in the cabin and the temperature gauge sits rock steady on the the warning lamp.
_________________
'84 Vanagon GL 1.9 WBX
'86 Westy Weekender Poptop/2.5 Subaru/5 Speed Posi/Audi Front Brakes/16 x 7 Mercedes Wheels - answers to 'Dixie'
@jakedevilliersmusic1
http://sites.google.com/site/subyjake/mydixiedarlin%27
www.crescentbeachguitar.com
www.thebassspa.com

[Kombi///M3]

I went with the Burley set up, none reverse manifold.
Used their coolant SS pipes. Works great. Same heat and
Temp gauge reading from my stock wbx. Running 02 ej25.
Good luck.

[davevickery]

[Edited] I see how this works now.

Kombi, I didn't know Burley had anything, so I pulled this off his website. His hot coolant goes to the pressure tank not back to the thermostat directly. So it would mix in the expansion tank and average out the temperature before reaching the thermostat. Maybe that isn't ideal for thermostat feedback, but it provides good air bleeding into the pressure tank. And the other side of the manifold goes out to the heaters before coming back to the thermostat. So there is no direct hot coolant feed to the thermostat, particularly if the heaters are on. But I can see why this would work pretty well. Possibly in winter with the heaters on, it could run somewhat hotter but most people don't have that issue anyway.

[Kombi///M3]

I have the same piping.. there’s another pipe that goes from rad to thermostat.
Seems to work for me.. but somebody chime in. I’ve been wondering why my rad fan not coming on since the conv. But my temp needle is been good. I tapped in the vw temp sensor to the coolant manifold too.

[wcdennis]

[davevickery]

You're right Dennis some people will say "rock steady" temps or similar things when that isn't totally accurate. That can make it hard to tell what one should expect.

But I recognize his symptoms. His could be different from what I experienced, but regardless I don't think it's normal. In my case, I found the problem and noticed the difference after I fixed it. And I believe there are hundreds of conversions running around out there with the same problem. Many converters are not aware of the need for continuous air bleeding or how little changes might affect the cooling setup.

It can be hard to troubleshoot if air gets in only occasionally under the right conditions and then gets purged out at other times like after using the heater. That is when they start pointing at all sorts of things like head gaskets and sticky thermostats. People also recommend Tom Shiels thermostat housing for a whole host of issues that it was not designed for. It may help in some cases but generally people see sporadic temp fluctuations and think they need better thermostat feedback and don't find the real issue. For example his thermostat housing was designed only to address overheating in winter conditions, so people with summertime temp fluctuations are barking up the wrong tree.

My gauge stays right on the middle of the LED and the fan cycles on low in stop and go traffic even if it is hot. If I have the AC on, the fan runs continuously so the temps stays low in stop and go traffic. On a long steep grade in 2nd gear, the needle will move just to the top of the LED, but not above it, before the high speed fan kicks on. That has only happened twice in 2 years and I just shut the AC off if I am pushing the van that hard. Occasionally on rolling hills at 50-55mph with grades that make it hard to keep in 4th gear, the high speed fan will kick on and I loose my AC. If I shift down to 3rd to take the load off the engine, I can have my AC back, or if I drive faster to get into the power band I can stay in fourth and not have high speed fan come on. This happens in hot weather but is more related to how hard I'm pushing the van. I noticed the hit to power with the bigger tires causing this more than my previous 27" tires. But the coolant temp doesn't fluctuate much (I haven't measured it lately) but the needle only moves to the top of the LED under worst case scenarios. Previously I was seeing temps over 200 and a couple times I heard spot boiling inside the engine after stopping to see what the trouble was. That was caused by small pockets of air in the system.

Going down long grades in winter, the gauge needle will drop below the LED but not low enough to stop providing heat like it did with my other KEP subaruvanagon and IIRC stock engines.

[danfromsyr]

220* isn't a 'high' temp

there is a reason that VW used a analog sliding gauge vs a direct numeric readout..
numbers cause people to worry about minor natural fluctuations in real time.
_________________

[davevickery]

Looks like the OP has left the building. But here is another coolant diagram worth sticking in this thread. This is from smallcar's website. They make their own proprietary reversed manifold but they also offer a wrap around the back option for non reversed manifolds and sell a pipe that is similar to Burley's pipe except the 5/8" port that goes to the top of the expansion tank is at the end of their pipe and Burley's is at the beginning (smallcars is right next to where most people put the expansion tank).

Small car non reversed coolant pipe.

Smallcar system drawing from their website. They don't have a drawing for the non reversed manifold so you would have to use your imagination on what would be different. But here they show one port going to the top of expansion tank and one port teeing directly back to the thermostat and another for the heater feed.

The main difference with their design is that the flow out of the expansion tank goes to the the radiator return line instead of the heater return line. That might make initial filling of the system easier. The heaters are fed from a separate port so it doesn't matter if the heater valves are closed, there will still be continual flow through the expansion tank to remove any air.

I think it helps to see the differences between coolant diagrams because you get a feel for how they all solve the 2 issues of providing continual air bleeding, and putting hot coolant directly on the thermostat.

[davevickery]