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Full Version: Engine preheat hose to the boiler
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First I would like to say thank you from the bottom of my heart to
all of you on this sight. I purchased my 1999 lxi in the fall of 2012,it needed
some work like they all do at that age. My family has traveled now to all four
corners of this great nation in my bird. We would not be able to do that without all of the knowledge I have gained from this web sight. You guys
are an indispensable source of inspiration and knowledge.
I will try and find an appropriate place on the sight to put pics and descriptions of all the work I have done so far.
But my question of the day, has any one had to replace the engine preheat
hoses from the series 60 engine to the boiler yet ? Mine have ruptured 3 times now in the last two years and left us on the side of the road. I keep splicing but the hose is just shot.
There is two shut off valves on the block but they do not close this circuit off.
The hoses run inside the frame rail and are totally inaccessible from what i can see. I ripped the bedroom floor up last summer on vacation and had two
more ball valves installed to close off that circuit.I will send pics latter.
They leave the engine 1" and are coming into the boiler at 5/8 and 5/8 if I remember properly , i will check today.


Pat Roys
Hopkins Mi
I will look for a diagram in my files. may be that they leave the engine going to the chassis heat in cockpit and the engine heat switch is just a pump that runs the flow when requested. plumbed in a way that the chassis heat can be shutdown and engine preheat only used.
That would be awesome Greg,I hope you can find a diagram or schematic
for the routing and size of hose used. I have pretty complete records for mine
but have found absolutely nothing on this subject. And I have found nothing on the web saying anybody else ever replaced these hoses on there LXI.

Thanks again,
The Aquahot in my last bus was early setup and the ah dealer did not understand how it was setup. we had a bit of a discussion about two system coolant loops where he claimed the AH used the coolant from the engine and engine 12 gal contents as the reservoir. I was not able to convince him that the systems were separate and unique.

On my prior bus 94pt Bluebird set up there is a transfer heat ex changer in a wheel well where the detroit coolant loop was not part of the AH coolant loop heat system. the two closed systems meet at a Transfer heat exchanger . the 94 was a Wabasto burner more or less and the motoraid waterheater and interior registers was part of that system detached from the detroit . I think it is necessary to differentiate the term heat exchanger and Transfer heat exchanger because the interior radiators and bay radiators are called heat exchangers in the AH manuals . The aquahot system in my lxi and your bus is likely a 431-12 . AH has manuals online
The install instructions show engine coolant being introduced as a separate loop but I do not see an actual plumbing depictions other than inlet and outlet. since it does not say that engine coolant is necessary and the expansion tank is included with the other three zones I would say there are two coolant paths and loops to the ah burner. check out notes page 19.
this does not mean that Bluebird did not tie the engine coolant look to the two plastic expansion tank loops and introduce a Transfer Heat exchanger some place under the frame rails ? I guess coolant color difference may be a tall tell sign if you have different detroit coolant color.
If you are close to this junk yard, you may get a good insight on the methods employed.
I found no documentation of the plumbing of the detroit to the front chassis heat system or connection to the AH sorry I will have a look if I get around to dropping the LP tank as planned

I plan to make up a loop for the inlet and exit of the Detroit coolant lines you found for use if I find an issue while traveling. the damage to your system may be the result of someone confused with the plumbing employed and there being a dead end in the Detroit loop to the front chassis heat. Or a switch in the pump control wires that start the engine preheat pump there is a warning in the engine preheat Wanderlodge owners manual that I can vaguely remember . One other thing that comes to mind with the AH engine heat pump is: if they use a Transfer heat ex changerer there will need to be another pump to flow fluids from and to the detroit and it may or may not loop to the chassis heat?
Hi Greg,
Thanks so much for taking the time to get that info for me. I crawled under
the bird tonight and it looks like BB ran two 1" gates green stripe II hoses
from the left hand side of the engine and BB did install ball valve shut off's
on both of them. I can also see two hoses coming off the engine near the left upper area of the engine. These are the two hose that run to the aqua
hot for engine preheat. These are the two that I removed the bedroom floor
to axcess last summer when the aquahot preheat hose blew on vacation.
Then I installed ball valves and shut off that circuit. I will update you tommorrow on the size and type of hose coming ot of the aqua hot.

Thanks again
I got under there again and have attached the pics of the hose in the aqua hot area.
The first pic is the engine supply hose (factory installed 5/8 goodyear highmiler)
The second is the engine return hose (factory installed 5/8 cheap standard hose)This is the one that is shot and I have spliced 3 times.
The third is were I spliced it above the aqua hot.
What is confusing is the fact that both of the hoses left the engine as the
premium highmiler hose. I wonder if Bluebird ran short on this hose during
original build ? After build it is totally inaccessible to be able to splice.
I have all of the records from the time of 1st owner and do not find anywhere
that somebody worked on this issue.
I will post pics of the shut off valves later.

Pat Roys
Hopkins Mi

[attachment=2141][attachment=2142][attachment=2143][attachment=2144] Here are the pics of the engine shut off valves.
1st pic is factory original 1" shut off going to dash heat.
2nd pick is factory original 1" shut of going to dash heat.
I would assume that the 2nd pic of the hose coming out of the water pump
would be supply and the 1st would be return.
3rd and 4th pics are the two ball valves I had installed last year on vacation when the 5/8 hose kept blowing at the aqua hot.
I know they are not the greatest pictures of the new valves but I took them
laying under the bus and they are about 5 feet above you from that position.
It apears that BB used a premium gates green stripe II hose for the 1"

is there two paths for Detroit heated coolant?and are the two paths closed loops and not joined at some point? I looked and looked for a diagram for the Detroit to aqua hot in this and my prior wanderlodge and found that every and each is unique. may be that built on Monday is different then built on Wednesday
thanks for the images I need to investigate my setup so I know how to band aid it in the event of an issue may be best to just loop the in and outs in the engine compartment to limp home
Hi Greg,
I will say after getting into my LXI coolant hose issues, the only way to
access the hoses going to the Aqua hot is the removable bedroom floor panel to access the top of the engine. No fun !

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