Gumbo_

Hi all, new subscriber from Italy.

I am restoring an 88 model, 2.1 Turbo diesel motor (which I just rebuilt from scratch).
The truck was hacked real bad by previous owner(s), and among the things that were hacked/modified is the heating core was bypassed/disconnected.
I've got the two pipes from the heater core on the firewall and a stump of what appears to be a cut white vacuum line near the two pipes and that's it....

The truck has no AC (it was an optional feature), which to me is a good thing as the Renault TD motor is well known for overheating even without AC, which in my area is not really needed even during summer.
The vent system is working fine. There must be a leak somewhere in the vacuum system because at idle the air is directed only to the windshield (and the "PART TIME" light goes off)
Fixing this leak is not a priority though, since starting at 1200 rpm I've got vacuum. Planning to look into the vacuum leak matter sooner or later but not now.
I would like to address the heater core issue ASAP as the time of the year requires some heating and defrosting of the windshield.

I am not at all sure the heater is damaged - could be it was bypassed because previous owner (who is evidently a jerk) was trying to improve the cooling system, same reason why he removed the fan shroud..... Or maybe its plugged and can be flushed.

So I am planning to check the heater core with water hose and see what happen - plugged, leaks, holds pressure etc.
However before I do all this I would like to know how the heating system functions on this truck.
Can I just restore circulation in the heater core, or I need some kind of actuator to allow circulation of the coolant into the heater only when I set the temp to warm ?
When I move the **** from cold to warm I hear something moving/shifting independently of the vacuum, so I believe that part of the vent system must be manual, not vacuum operated.

If an actuator is actually required would it be possible to replace it with a manual valve that I may open in fall and close when the weather gets warm in spring/summer ?
I have no experience at all with vacuum systems and (at least as a temporary fix) I'd rather install a manual valve then messing with the vacuum system to restore the original system.

Thanks in advance to anyone who will help me solve this issue.

cruiser54

This may help.

Gumbo_

@ Cruiser54, thank you for the diagram. As I said I am not much concerned about the vacuum leaks as I have enough vacuum when the truck is being driven, but .I will look into it with the help of the diagram you posted.
The question is what should I do to restore the circulation to the heater core.

I mean do I just just hook the coolant pipes back to the core ? I have no idea how the piping was designed before being bypassed.
Do the original circuit has some kind of valve (be it vacuum operated or otherwise) that will let hot coolant flow into the heater core only when I shift the temp **** on the dash to warm ?
My truck did not come with A/C from the factory.

Here's two pics showing what's currently under my hood.
I wonder what's that small white tube poking out of the firewall near the heater core pipes and the (not original) expansion tank...

Gumbo_

Ok, I found this thread which answers my own question...

https://www.cherokeeforum.com/f2/wha...-valve-230998/

Original design had heater control valve, but it can be deleted. Good !
Hope the heater core is not rot and was bypassed due the valve leaking, so I can have some heating into the cab !

Still wonder what the purpose of the small white tube, since everything seems to work just fine with the vent controls...

Saudade

The control valve is/was vacuum operated. The white line gets connected to the valve. If you feel it drawing vacuum, just cap it off.

The upper port on the core looks capped off but the lower one is open. Just make sure you flush the core out before you connect it. Hopefully, it holds.

Gumbo_

Actually both ports were capped off. The lower one had a dry rot rubber cap that break off when I removed it..
Which one of the two ports is supposed to be the inlet ?
I am planning to test if it holds the pressure in a garden hose by plugging the outlet hose, but perhaps that would be too much.
The radiator cap holds a pressure of 15/20 psi, and I feel the pressure in the garden hose may exceed this value.

Maybe I should just check it for leaks as I flush it and forget about checking if it holds pressure ?

cruiser54

Hook it up and see if the core leaks.
As for where the hoses go from the engine to the core, it's hard for us to say unless someone who has the 2.1 can enlighten us.

Saudade

I haven't been able to locate much info on the 2.1T Diesel. However, it appears you still have an expansion tank (closed system). Do the hoses from the water pump/thermostat run directly to the tank?

Gumbo_

I flushed the heater core today and to my suprise not only it was not clogged but the water was clear and not muddy as in pictures I've seen on the internet. Maybe due to the fact the core was dry/bypassed ?
I did not use any kind of chemical, not even vinegar. The water flows well with no apparent restrictions. I started with the faucet halway open and then to 3/4. I didn't run it full blast as in this area we've got high water pressure. I reversed the flow 7-8 times and overall I flushed the core for a half hour / 45 min. Everytime I reversed the flow a little dirt came out, and in the end almost nothing.
Here's a pic of the first flush (2 gallons bucket), the water is clear and not much crud either.


I am not sure where one is supposed to look for heater core leaks. I placed a dry mat under the dash (passenger side) but did not remove the carpet/lining. If the core leaks happen over the carpet, then my core has no leak at all. If they happen higher up at the firewall and then seep underneath the lining, I still believe I have no leaks because the lining appeared to be dry to the touch but this may require further (visual) investigation.

Now, how do I route the coolant to the heater core ?
First of all I am not sure what a "closed system" is. I don't think the radiator is original since it has a cap and it is a three cores copper unit, which I understand was an upgrade over the stock two core aluminum one. The tank for sure is not original and it has no pressure cap. The radiator cap instead has a pressure valve.

The hose from the water pump runs directly to the tank. Actually it's a straight metal tube that ends in a three ways T. One way goes to the tank, another goes to the head and the third one I couldn't figure out exactly where it goes, towards the rear of the block anyway.
The small outlet hose from the top of the tank goes to the neck of the radiator cap (not pictured below).



I guess the easiest thing to do would be putting the heater core between the T and the tank. I mean route the pipe that currently goes to the tank to the heater inlet and add a hose from the heater outlet to the tank. Not sure this is correct though.

cruiser54

the leak will appear on the passenger side floor when the system is under pressure.

Gumbo_

What do you mean "will appear" ? Coolant will drip upon the passenger floor/carpet from above or the passenger carpet gets soaked from underneath with no visible drippings ?
Any suggestion regarding the routing of the hoses to the heater that I proposed in my previous message ?

I.E. route the pipe that currently goes to the tank to the heater inlet and add a hose from the heater outlet to the tank

cruiser54

You will see the drippings.
On a 2.1 I have no idea which hose goes where. Can you tell by the different hose diameters?

Gumbo_

It's not a matter of what goes where in the stock circulation diagram, as the cooling system has evidently been reworked/rearranged, possibly due to the heavy duty radiator and tank swap.
I have not find any diagram but do have plenty pics of the same motor and the pipes are routed different than mine (and in mine some are missing altogether.)
Is there anything inherently wrong in my idea to place the heater on the path from the water pump to the tank ?

Rogue4x4

Don't listen to cruiser54, it's all an evil plan to get parts for his Alfa Romeo habits, haha


That said, all jokes aside, listen to cruiser54. I trust him with my life.

Rogue4x4

BTW, he knows Alfas as well as his jeeps. A true master of the arts. Man can diagnose and solve problems faster than Google. Just search him first LMAO