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You need to join high pressure to low pressure to get flow. If you connect high to high like tapping the same hose a foot apart, you won't get any flow.
That's a good tap for the source but I would put the return somewhere else. It looks like there is a factory heater control valve on that circuit, assuming the valve works and is off (i.e. heat is off) then if you put your return after that valve then you would get flow as there's low pressure on the other side of that valve when it's shut.
You need to join high pressure to low pressure to get flow. If you connect high to high like tapping the same hose a foot apart, you won't get any flow.
That's a good tap for the source but I would put the return somewhere else. It looks like there is a factory heater control valve on that circuit, assuming the valve works and is off (i.e. heat is off) then if you put your return after that valve then you would get flow as there's low pressure on the other side of that valve when it's shut.
It's my impression that the heater control valve is more of a "Y" / selector than a on/off, and only brings the heater core in and out of the coolant loop (so after the valve coolant either goes through the heater core and into the return, or straight to the return). I haven't verified this, though, and would love an expert to chime in on the exact location of the return line. I've gone digging, but it's a little hard to tell without pulling things out of the engine bay.
It's my impression that the heater control valve is more of a "Y" / selector than a on/off, and only brings the heater core in and out of the coolant loop (so after the valve coolant either goes through the heater core and into the return, or straight to the return). I haven't verified this, though, and would love an expert to chime in on the exact location of the return line. I've gone digging, but it's a little hard to tell without pulling things out of the engine bay.
Nevermind. Initially I was thinking it wouldn't make that much of a difference, but I agree, performance would be better cutting the heater core(s) out of the loop, regardless. Anybody know where the final return line is for that coolant loop?
An update: I tried plumbing everything as originally drawn, and the two heater cores actually soaked up too much heat and the water didn't get hot enough. I dug around some more and found their return hoses (which combine at a T about a 8 inches rearward and 2 inches driver of the heater control valve and are routed into the back of the engine, either into the passenger valve cover or the intake casting--I can only tell by feel). After routing around the heater cores I was able to pull out enough heat to get on-demand shower water with plenty of flow.
During all of this, my scangauge read a water temp of no higher than 165 when not heating shower water, and around 150 when heating shower water. I was surprised that my water temperature wasn't getting to 185 (granted it was about 45 degrees out)... I felt the radiator and the radiator hose (when at 165) and they were both warm. After running the shower for a while, the radiator cooled. This leads me to believe that my thermostat is opening. Should it be? Is that normal? Should I be replacing the thermostat? Is it possible the previous owner put in a low-opening-temperature thermostat?
The radiator cooled because the thermostat closed trying to keep the heat in the engine, so that's a good thing. Your water to water heat exchanger is simply more effective than factory set up so it's pulling more heat out. As long as there's enough heat for your shower and the temps come up to normal when the shower isn't running you're good to go.
The radiator cooled because the thermostat closed trying to keep the heat in the engine, so that's a good thing. Your water to water heat exchanger is simply more effective than factory set up so it's pulling more heat out. As long as there's enough heat for your shower and the temps come up to normal when the shower isn't running you're good to go.
Yeah, I guess my concern lies down the road when I'm storing 10-ish gallons of water as a heat reservoir for a hydronic heating system. I'll have to cycle the engine less if I can store that water at a hotter temperature, and I was assuming I'd be able to get up to about 165 when my engine got up to about 185... Looking less like that's going to happen when it's cold. Do thermostats come on gradually at a temperature slightly below their "turn-on" temperature? Should I expect ~175F if I install a 195F thermostat?
Yes thermostats do transition from closed to fully open over something like a 20 degree spread. However if your current thermostat is already completely closed at 165 then there's nothing a "hotter" thermostat can do, closed is closed. At that point your limitation is how many BTUs the engine creates.
I don't know exactly what your setup is. If you're taking a constant source of cold water and heating it for a shower then there's not much you can do. More RPM will give you more heat, reduced timing will give you more heat, disabling the EGR will give you more heat.
If you're heating a tank of water and aren't introducing more cold water then you'll be able to get that water nearly up to the same temp as your coolant it's just going to take time. The engine duty cycle to maintain is then going to depend on the insulation of that tank.
Yes thermostats do transition from closed to fully open over something like a 20 degree spread. However if your current thermostat is already completely closed at 165 then there's nothing a "hotter" thermostat can do, closed is closed. At that point your limitation is how many BTUs the engine creates.
I don't know exactly what your setup is. If you're taking a constant source of cold water and heating it for a shower then there's not much you can do. More RPM will give you more heat, reduced timing will give you more heat, disabling the EGR will give you more heat.
If you're heating a tank of water and aren't introducing more cold water then you'll be able to get that water nearly up to the same temp as your coolant it's just going to take time. The engine duty cycle to maintain is then going to depend on the insulation of that tank.
Ok, cool, thanks for the help. Well I guess maybe I'll hafta swap in a 195F thermostat in the winters once I have the hot water tank installed.
About 4 weeks on the road, about 16 showers logged. Such a simple pleasure, but pretty satisfying when you're in the boonies. Plenty of almost-scalding hot water at ~1.5-2GPM for as long as you want. Next step might be to get a sump pump and about 100ft of hose for unlimited river showers.
Thanks a million for the photo, could you possibly add some arrows so i can follow direction (sp) of flow for Coolant and fresh water? I'm trying to figure that out. Example attached with you pic. Does everything stay under the hood or does your heat exchanger quick disconnect?
I have been considering a project like this for quite some time. Would be quite nice to have a quick, warm rinse after getting to a camping spot. Any chance I could bug you for a quick overview of part numbers? Thanks for sharing this project with the community.
The 3/4" high temp silicone hose (This stuff is wayyyy too expensive. You can get heater hose at autozone, etc. for much less. I like it because it's clear and very flexible and because I have had good luck in the past.)
Temperature gauges (let's me see coolant temp inbound and outbound. I was also going to use for water temp, but they don't fit with the spacing of the FNPT fittings built into the heat exchanger): https://www.supplyhouse.com/Cash-Acm...perature-Gauge
Hose clamps I had in the garage. It took ~22 iirc.
Yeah, no problem. Here are three of the paths highlighted.
This is the default coolant path that goes through the heater cores and bypasses the heat exchanger. This is "shower mode" which bypasses the heater cores and goes through the heat exchanger. This is the path for water pumped through the heat exchanger. Blue is cold water. Red is water that has been heated by the heat exchanger, and orange is water that has been mixed to almost-scalding by the thermostatic mixing valve.
The heat exchanger is velcro'ed to a wood plate which is velcro'ed to my battery. The wood is there so that I have some thermal & shock insulation between it and my battery. I had to leave the day after the install, so I put off fabbing & welding up a proper bracket. It survived the trip, though, so I may just leave it.
11-23-2018, 01:52 PM
