Coolant functional diagram for 1HD-T engine in HDJ81?

[83bj60]

Hey Folks,

I'm trying to understand the cooling system in my HDJ81. Can't find any information in my shop manual, and I don't have a factory manual.

I'd like to finally figure out how to install my engine heater!!!

A functional diagram of the cooling system would be greatly appreciated!!!

Chris

 

[83bj60]

Thermostat outlet/cold water return (?) on the 1HD-T ?!

Hey Folks,

I'm trying to understand the cooling system in my HDJ81. Can't find any information in my shop manual, and I don't have a factory manual.

I'd like to finally figure out how to install my engine heater!!!

A functional diagram of the cooling system would be greatly appreciated!!!

Chris

Well for now the canister heater project has been shelved indefinitely for now. Seems no one likes them and recommends installing them so I'll have to pass. I have other plans for it so it's not a lost cause.

I still cannot understand how a lower rad hose heater can work on this beast. The lower rad hose is essentially flat and is connected to a cast aluminum part that incorporates the thermostat housing.

If someone who as actually installed a rad hose heater on one of these hoses without major mods can tell me how they managed to establish a proper convection flow with this setup, I'd love to hear about their story.

Secondly, I'd love to get a part number for this stupid casting. It seems to me that the outlet pipe is totally useless. I'm considering cutting it off so that I may install an internal heater in a vertical section of hose so that proper convection can be established.

Lastly, can Wayne or someone else who has installed a heater and looked at thisn setup in a garage tell me how water flows in that thermostat housing/lower rad hose connector? It simply doesn't make any sense to me. For now, I'm going on faith. Baaad!

I'm at my wit's end and about to completely redesign that stupid thermostat housing/lower rad hose connector. Please tell em I'm wrong and there is some hidden purpose as to why does the thermostat housing connect to the cold water return (instead of on the hot water outlet like on every other engine I've seen) and why did they have to extend a rigid pipe section all the way down to the level of the radiator bottom outlet?

Frustrated by -30

 

[crushers]

i can not post up a diagram but i can describe it:
factory manual page CO3
The cooling system is comprised of the water jacket, rad, waterpump, thermostate, cooling fan and other components.
coolant which is heatedin the water jacketis pumped into the radiator via the upper rad hose where is is cooled by the cooling fan and the vehicle windstream.
coolant which has been cooled is then sent back into the engine by the lower rad hose by the water pump, where it cools the engine.
the water jacket is a network of channels in the shell of the cylinder block and cylinder head through which the coolant passes.

thermostate:
the thermostate is a wax type by-pass valve and is mounted in the cylinder block. the thermostate includes a type of automatic valve operated by fluctuations in the coolant tempurature. this valve closes when the coolant tempurateure drops preventing the circulation of coolant through the radiator and thus permitting the engine to warm up rapidly.
the valve uopens when the coolant temp has risen allosing the circulation of coolant
(BJ60, this is where the convestion heater does its job, the thermostate opens and allows the heated water to circualte though out the rad and block)
Wax inside the thermostate expands when heated and contracts when cooled heating the wax thus generates pressure which overcomes the force of the spring which keeps the valve closed thus opening the vavle.
when teh wax cools its contraction causes the force of the spring to take effect once more closing the valve.
the therostate in this engine operates at a temperature of 76G (169 F)

hope this helps...now start translating the report for us...

 

[83bj60]

It doesn't make sense!!!

i can not post up a diagram but i can describe it:
factory manual page CO3

OK, don't have it.

coolant which has been cooled is then sent back into the engine by the lower rad hose by the water pump, where it cools the engine.

the [thermostat] valve opens when the coolant temp has risen allosing the circulation of coolant

What I don't understand is where in this circuit is the thermostat installed. Looking at the thermostat housing, which includes the radiator cold return line, you would think that the thermostat is mounted on the cold side, but it doesn't make sense.

(BJ60, this is where the convestion heater does its job, the thermostate opens and allows the heated water to circualte though out the rad and block)

How can the heater do its job if it has to pass through the rad first? It doesn't make sense!

hope this helps...now start translating the report for us...

I wish it did but it doesn't... There is something I'm not getting here. If the coolant gets back into the engine the normal way (from the bottom), then circulation must go from the bottom hose to the thermostat housing, so it has to go up, not through the rad first, it has to come from the rad. I'm going to check it out tomorrow with a thermometer to make sure.

As for the translation... Just send it to me

Chris

 

[crushers]

dude,
quit overthinking things (maybe it is the french way, i don't know but it sure seems to me it is. every french person i have ever met does it)
as long as there is a restriction in the system a thermostate works...i.e. the thermostate is the restriction.

if you don't understand it then install the damn heater and be done with it...or don't it is your chioice. one mornign at 3AM the understanding will hit you till then forget about it...or don't it is up to you.

for me life is too short to worry about things that work,

BTW, did you note the different in thermostate opening temp? 79C vs the normal 88C? hence the cold side of the rad? upper rad hose 88C, lower rad hose 79C...

 

[roscoFJ73]

I wish it did but it doesn't... There is something I'm not getting here. If the coolant gets back into the engine the normal way (from the bottom), then circulation must go from the bottom hose to the thermostat housing, so it has to go up, not through the rad first, it has to come from the rad. I'm going to check it out tomorrow with a thermometer to make sure.

As for the translation... Just send it to me

Chris

The thermostat is heated from coolant inside the engine block,not from the lower radiator hose.
The thermostat is fitted at the junction of the inlet pipe and the engine but the wax pellet sits facing the engine.
However if you instal the heater on the lower radiator hose,the convection should keep the thermostat open and thus warm the block,provided the heater can keep the coolant to the opening temp of the thermo.

WAYNE ,My FSM says the thermo opens at 74-78c and should be fully open by 10mm at 90c

 

[crushers]

is that page CO-3?

 

[Kalawang]

I have no idea and no hope of understanding what you guys are talking about. Lucky for me I live in the tropics. When my thermostat sprung a leak, I simply bypassed it.


Kalawang

 

[roscoFJ73]

is that page CO-3?

yes

 

[crushers]

hummm, my post was directly from the factory service manual publication number RM172E????

 

[roscoFJ73]

hummm, my post was directly from the factory service manual publication number RM172E????

I was actually looking at CO10 ,sorry,but C03 says it operates at 76c.
It is RM172E Im reading.

 

[matt 105]

Kalawang " I have no idea and no hope of understanding what you guys are talking about. Lucky for me I live in the tropics. When my thermostat sprung a leak, I simply bypassed it."


OK, the the other thing about themostats is that they put a restriction in the system, to slow down the flow of coolant, so it has time to remove the heat from the block. When ppl remove a themostat, they notice that the temp gauge reads lower,as the cooant will be cooler, but your oil temp will be higher - this is the true measure of engine temp.
Heres something to think about, I measured the waterpump pressure on a 38L Cummins the other day at 35PSI (spec is 30 - 36PSI), but that engine runs a 7PSI radiator cap.
Matt

 

[crushers]

I was actually looking at CO10 ,sorry,but C03 says it operates at 76c.
It is RM172E Im reading.

yep, my bad it does read 76C, thanks for the correction...

 

[Kalawang]

Hi Matt,

When my thermostat sprung a leak I couldn't find a replacement. Still haven't.

My temp gauge actually reflects a higher temperature these days as I use less coolant than before on the theory that water cools an engine better than coolant. The coolant is just to keep the water from boiling away and thereby reduces or eliminates the need for replenishment. I think the radiator of the 1HD-T is so large that it could probably function well without the coolant, but the coolant also has anti-rust functions so I use it.

I don't know what my oil temperature is, and have no convenient means of checking it.

I did the bypass about 3 and a half years ago and have not noticed any problems or any deterioration in performance. Warming up the engine takes about 30 seconds more than in the past, but I'm not sure of that. It isn't a significant difference to me.

Thanks for the heads up. I'll try to see if I can find a way of monitoring the oil temp. Maybe theres a gauge out there somewhere.


Kalawang

Kalawang " I have no idea and no hope of understanding what you guys are talking about. Lucky for me I live in the tropics. When my thermostat sprung a leak, I simply bypassed it."


OK, the the other thing about themostats is that they put a restriction in the system, to slow down the flow of coolant, so it has time to remove the heat from the block. When ppl remove a themostat, they notice that the temp gauge reads lower,as the cooant will be cooler, but your oil temp will be higher - this is the true measure of engine temp.
Heres something to think about, I measured the waterpump pressure on a 38L Cummins the other day at 35PSI (spec is 30 - 36PSI), but that engine runs a 7PSI radiator cap.
Matt

 

[matt 105]

Gday Kalawang and all,
Im wondering now what you mean by t.stat sprung a leak?
Another thing good coolant does is reduce cavitation in diesels. That is where bubbles of oxygen are formed, by the shockwave from ignition, against the cylinder walls. These bubbles boil off with enough energy to erode away the cylinder liners, or in your case, your block. - Or something like that.
IIRC.
There might be something about electrolosis and dissimilar metals in there as well.....and being kind to the water pump seal.
- sorry , I never paid much attention past "coolant good - water bad"
For mine, I would order a new t.stat and gasket, and 6 liters (the old stuff you mix 50/50 with demin. water) of Toyota long life (nice red stuff) coolant.
I love that stuff more than even Tec50!
Might be less hassle than an oil temp gauge set up?
Regards
Matt
off to work for a week

 

[83bj60]

The thermostat is heated from coolant inside the engine block,not from the lower radiator hose.
The thermostat is fitted at the junction of the inlet pipe and the engine but the wax pellet sits facing the engine.
However if you instal the heater on the lower radiator hose,the convection should keep the thermostat open and thus warm the block,provided the heater can keep the coolant to the opening temp of the thermo.

WAYNE ,My FSM says the thermo opens at 74-78c and should be fully open by 10mm at 90c

Excellent answer, that's what I was looking for, thanks Rosco!

 

[83bj60]

dude,
quit overthinking things (maybe it is the french way, i don't know but it sure seems to me it is. every french person i have ever met does it)

Well, you talk exactly like my old partner used to. A real Redneck, but a lovable guy nevertheless. I was constantly correcting his mistakes, but he would be the one to get things started

I have fond memories of him, although he cost me a lot of money and we no longer talk as a consequence; I do miss him on a personal level, though.

In any case, you have sized me up exactly... I'm the type of guy to 'measure many times, cut once'...



Anyway, our resident Bumbling Sherriff answered the question very nicely... As for taking the housing off, it's going to be a job at -20C in the snow since the AC compressor and the alternator are in the way so... I'll have to wait till I get some serious (heated) garage space to work on this and my other projects. My buddy Pierre is going to get the old 60 back in excahnge for a mounted 3B motor and tranny for my biodoesel/generator experiment, so I'll probably be getting some garage space at the time as he's going to rebuild the 60 for himself...

Back to work now, see ya tonight...

 

[crushers]

why are you removing the housing?

 

[-uhuru-]

Here is an example of what happens when you use water instead of coolant.

Notice the holes on the water to oil cooler of a 1HD-T engine.

Hueco means hole in Spanish !

 

[83bj60]

why are you removing the housing?

Aha! Very inquisitive, and I'd like to keep the details secret at this point as I want to make sure it is reasonably easy to do. Essentially, I intend to modify the lower part of the housing where it connects with the rad hose so I may install an immersion heater in a vertical poistion. I will only do it if it is not too difficult to remove it, as I'm unsure how much work it would take to remove the AC compressor and the alternator. My first first idea was to install heaters in the block, but that would have required removing the injection pump, oil filter housing and other paraphernalia. But I still have a two other options up my sleeve...

The idea is to make it possible for the engine to very quickly rise at operating temperature using household electricity without the need to install an external oil fired furnace.