where_the_heffalump_roams 917 AF

[where_the_heffalump_roams]

It's hard to tell in the above pic, but the exit fuel line from the filter is actually just a bit smaller than the feed line. I could have written the size wrong. But it is the smallest hose I could get that would fit the fuel filter and the reducer supplied from Webasto (the inlet and outlet for the pump is quite small).
As of right now, the line is primed and hasn't presented any issues as of yet. I could shorten the line between the filter and the pump, but not by much. I also looked back at old pics of when I first bought the heffalump. At that time, it looks like the filter was horizontally mounted just 1-2 centimeters away from the fuel pump inlet. Not sure if that matters?

 

[where_the_heffalump_roams]

You are correct, they do not need to be separated by a heat exchanger. However, this is probably the only truck with a hydronic system that I have heard of that isn't.

It's pretty standard to stop all the bits of metal and crud that circulates around a cast iron engine block being pushed through the heating system and the heater.
It also means that the two loops can work at different pressures. Lastly it means you can have radiators in the living area higher than the engine expansion tank. By looping them together, your highest radiator in the system becomes the expansion tank, that isn't good.

But you are correct, they don't need to be, but it is good practice

Neil

Thanks for this little tid bit of knowledge. I'm a def no mechanic and I'm trying to better understand these systems. So a heat exchanger serves a mid point? If I understand correctly, it was basically be adding a 3rd loop into the system that separates the other two? The webasto could feed a heat exchanger which in turn would accept circulation fluid from 1. engine block 2. habitat radiators. If that is correct, I'm assuming the another pump would have to be added to circulate fluid from the habitat radiators to the heat exchanger?

 

[Neil]

Hi, no it's not really a third loop.

At the moment, from what I understand , your system is one continuous loop through the cabin heating and the engine block. You loop can be devided into two manually by closing some valves.
This is not good practice as the dirty water from the engine block is now in your heating circuit.
The standard way to keep them seperate is simply to divide the two parts of the loop permenantly with a small plate heat exchanger . This means that the fluid from the engine is completely seperate. The two loops simply kiss each other .
There are many advantages to this, which is why it is a pretty standard approach with hydonic systems.
1. If you develop a leak in either circuit, it doesn't affect the other
2. You cabin heating circuit can run at its desired low pressure, leaving the engine to run at its much higher pressure. At tge moment your cabin system will be at too high a pressure.
3. You can have radiators in the cabin higher than the engine expansion tank without fear of filling your highest one them up with air. ( I suspect the highest radiator currently needs bleeding often )
4. You don't clog up your heater and cabin pump with engine debri.
5. You will never accidently end up heating the engine block because you forgot to close the valve

This is the standard way to fit hydronic heating systems, your , although it works, isn't, for the above reasons.

However, you will need to wire in a switch to activate your cabin heating circuit independently of the heater being on.

This allows you to simply turn on the pump whilst driving and heat the cabin and hot water.

You will also need to add a small electric pump on the engine circuit. This allows you to circulate hot water through the engine to pre heat it whilst stationary.

It's quite a simple and cheap modification .

Hope this helps, but I suspect this modification will be quite low on your to do list, having read this thread.
You have lots to fix first
Good luck

Neil

 

[where_the_heffalump_roams]

Thanks that is helpful and sounds like good practice.
And you are correct in terms of priorities though there has been some big boxes checked recently.

Recently, the guys at Sacramento Spring were able to take my old broken spring and combine it with parts with an existing leaf spring to improve the alignment on the rear axel. It was off about 6.5. cm before from axel to axel! I'm hoping this removed the crab walk that the truck had.They are super rad guys and referred me to a mechanic who came out their lot and removed/reinstalled the leaf spring.


The plan was to meet up with that same guy this week to help with the damaged air lines and hydraulics on the front bumper. There are some big leaks around the PTO and cab lift that need to be addressed. But that didn't work out to I headed to Nevada between work shifts for help with an alignment and brakes. Finding a shop that could help with the brakes has been challenging. I've been hauling a set of brake liners and drums around with me for most of the year. I had stopped by John Spring and Suspension in Reno earlier. They are the ones that figured out the truck had asymmetrical lengthen leaf springs that were causing the crab walk. The guy that does the alignments ended up being sick this week but the owner let me use the lot and referred me to a Big Rig Mobile Repair for help.

Just across the street is an old school shop that is literally the only place I could find that would install the liners on the shoes. After the shoes were removed, I simply walked them across the street and they had them ready in less than 2 hours! Not only that, they had cleaned them up and painted them.

You can see the front brakes had gone critical who knows how long ago. One of the liners had even gotten down to the rivets and the drums were completely shot.


Unfortunately, the re-install wasn't uneventful. The new liners had so much thickness that the drums wouldn't cleared them. At this point, I was beyond grateful to be at that exact site vs having the shoes/liners shipped out. The owners from Reno Brake, walked over, looked at the problem, and simply took the shoes back to machine off a bit of material to clear the drums. This took them about 10-20 minutes total and they refused to charge me extra. In fact, they only changed me around $75 for reline/paint the shoes!!! After the brakes were fitted, I test drove the heffalump around the block and was very stoked to have solid front brakes. What a huge difference in driving and it really adds a very thick layer of safety. Afterward, I had to argue with the mechanic about pricing. He tried to under-bill me for his services. After some back and forth, we finally agreed on a bill that was nearly double what he tried to charge me originally.
While the work was being done. The oner of John Spring came out and chatted. He is a super rad, humble, and honest individual. He seasoned traveler that experienced the world in and out of the military. I really wanted to get a pic of him with the truck, but he was tied up with customers as I was leaving. I really can't overstate what a great feeling it is to have this work done through such a positive consumer experience. The rears will still need to be serviced at some point, the pads are worn unevenly and there is plenty of pad life for now. What a big relief it is to have these brakes serviced. The driving experience is like night/day and it's just that much more safer. If feels like some momentum is finally being created in getting this truck back to where it should be. I'll share more later and in the next post.

 

[Neil]

Agreed, you definitely have your work cut out there.

Neil

 

[Pacific Northwest yetti]

John's Springs are rad. Just solid dudes. We need more shops like that in the world. Just good humans.

 

[where_the_heffalump_roams]

John's Springs are rad. Just solid dudes. We need more shops like that in the world. Just good humans.

It really feels like a come back after experiencing the worst treatment I have ever had as a consumer when the motor cradle had to be repaired.
And the guys across the street, Reno Brake (they also paint), are equally as solid. It was a win situation all around.
I didn't want to be too nosey and while the mechanic did his thing. But the front brake system looked very basic and serviceable. Something I think I can try to tackle in the future if needed.

 

[joeblack5]

You are correct, they do not need to be separated by a heat exchanger. However, this is probably the only truck with a hydronic system that I have heard of that isn't.

It's pretty standard to stop all the bits of metal and crud that circulates around a cast iron engine block being pushed through the heating system and the heater.
It also means that the two loops can work at different pressures. Lastly it means you can have radiators in the living area higher than the engine expansion tank. By looping them together, your highest radiator in the system becomes the expansion tank, that isn't good.

But you are correct, they don't need to be, but it is good practice

Neil

I do not agree with the above, sofar in commercial buses, tractor trailers and just as in the webasto / eberspaecher manuals there is no use of a heat exchanger.

The engine coolant, crud and all goes happily thru the interior heat exchangers in every car and truck ,sometimes with assistance of a booster pump.

Our city bus with HVAC on the roof had the proheat just next to the engine and no heat exchanger, booster pump yes.

The only possible reason to have a heat exchanger is if you are tied in with your domestic hot water where a leak could could contaminate your drinking water, or if you use pex floor heat that could fail from over temp. and overpressure.


Extra parts , extra complexity, extra expense, extra maintenance.

Johan.

 

[Neil]

It's a personal choice.

All the big manufacturers of of overland trucks, mostly German or Swiss, will always add a hheat exchanger for the reasons above.

The biggest reasons is to stop your highest radiator becoming your engines expansion tank and to keep the pressure in your cabin circuit lower than your engine.

We have all see the pressure that can build up when a radiator cap is removed from a hot engine.

Do you really want this pressure in your domestic loop . I wouldnt

As I said you don't need to, but its good practice as demonstrated by all the big manufacturers.

In the great scheme of things, the added expense is probably about a couple of hundred dollars.

If it works for you then its good

Neil

 

[joeblack5]

Neil, I can see that. The overlander industry plays with big money.. of course you expect something to go wrong with your domestic and you have to open it up then it is convenient that there is a heat exchanger in between.
Every school bus in the USA is without heat exchanger and there are several heaters that potentially expose children to scalding coolant.
So I think unless the company is not sure about their design it might me more a matter of liability.
For sure webasto does not care about roque engine particulates damaging the heating circuit.

I am also not sure if the highest radiator is a supposed problem why all roof hvac buses seem to purr along with a lot of miles..

Maybe a theoretical problem waiting for an expensive solution

But a personal choice is fine.

Johan

 

[where_the_heffalump_roams]

Reading through all and trying to better understand the system. The past 2 owners utilized the heffalump quite extensively and as far as I know. Didn't' have any large issues with contamination or pressures (that have showed up yet).
But I do see the benefit of having a safety margin. Partially if there is a leak in one system.
I'm also wondering about a heated radiator/towel bar that is the highest point in the system. About 1/3 of if actually gets heated. I don't know if that is how it is designed, or is it because it works as an expansion take as mentioned above. If that whole unit can be heated, that would greatly improve heating capabilities and make the system that more efficient.

 

[Neil]

On a previous thread, Joe stated he had to bleed that regularly. I think it where all the air ends up .

Neil

 

[Joe917]

I did not bleed it regularly. The top 3 bars always ended up with air and I left it that way. That bathroom is so small it heats in not time.

 

[Joe917]

The engine crud in the coolant circuit argument is just a non starter. If you have that much crud you need to flush and replace your coolant! I do maybe see the point about the air in the high rad, but in 10 years in the vehicle it was a non issue. Safety factor, it is oxygen barrier pex rated to 125 psi @180F.

 

[loonwheeler]

Max possible pressure for a combined coolant circuit would be equal to the pressure rating if the radiator cap, no? Our trucks cap is rated at 1.7 bar, not exactly high pressure.