1974 FJ40 Heater Performance Poor (1 Viewer)

[Jeremyrig]

Hi all,

I’ve been working to improve my heater performance reading everything I can find on here. Thus far i’ve reconditioned the heater box, disassembled the electron motor and cleaned it up, doubled the travel on the heat knob for how much flow, cleaned out the heater core and replaced with thermostat with a new OEM part. The i’ve improved the temp coming out from 85 to 100 degrees but from what i’ve read I should be getting 120-130. I haven’t flushed it yet but don’t see how that would make much of a difference but will do that next. After a 30 minute drive tonight with the new thermostat, i can put my hand on the radiator without it burning me, is that normal? What else could keep my 2F from warming up or could it be restricted flow. Maybe i bypass the heater knob valve?

Any/all advice would be greatly appreciated!!

 

[3_puppies]

performance of the heater is tied to the engine. you need to know the temp of the engine, which sounds low.
did you install the rubber on top of the thermostat?
you need to get the engine temp figured out before the heater

 

[Jeremyrig]

performance of the heater is tied to the engine. you need to know the temp of the engine, which sounds low.
did you install the rubber on top of the thermostat?
you need to get the engine temp figured out before the heater

Thanks, I did install the gasket on top and do you think I should add a temp gauge?

 

[SteveH]

cleaned out the heater core

If your heater core is massively coated with scale inside, you might consider removing it and filling it with muriatic acid to clean it out. There are threads on how to do this. But, as others mentioned, be sure you engine is at full temp and all heater valves are open and allowing coolant to flow. Grab both heater lines (to and from the heater) and you should feel a significant difference in temperature if the heater is working. An Infrared thermometer could be a useful tool in finding out how hot the engine is, too.

 

[AntFarm]

I would start by troubleshooting the basics on this one. Your cooling system might need a full refresh as many of them do. It sounds like you either have an open thermostat which leads to super slow warm-up of everything, or you have a flow restriction somewhere, leading to no hot water going to the heater core. Feel all hoses with your bare hands as the engine warms up to determine the way ahead. When you replaced the thermostat, how was the condition of the thermostat housing? Corrosion and scale buildup in the housing means it likely exists throughout the cooling system as well. Is your heater T on the lower radiator hose in good shape? Is the heater T hot and flowing hot coolant back to the firewall? Just need to investigate further. A properly operating Thermostat should open within a few minutes of starting the engine and start to warm up the upper radiator hose fairly quickly. An idling truck in your driveway should have a warm radiator top in about 10 minutes or so as long as the ambient temps in your neighborhood aren't below about 40 degrees-ish.

 

[Jeremyrig]

cleaned out the heater core

If your heater core is massively coated with scale inside, you might consider removing it and filling it with muriatic acid to clean it out. There are threads on how to do this. But, as others mentioned, be sure you engine is at full temp and all heater valves are open and allowing coolant to flow. Grab both heater lines (to and from the heater) and you should feel a significant difference in temperature if the heater is working. An Infrared thermometer could be a useful tool in finding out how hot the engine is, too.

Thank you, I did fill and submerse the core in CLR for a stint, cleaned out all the debris. I think my next steps are confirming Toyota sold me the correct thermostat, double check the fluid level, try that trick of holding the top radiator hose while it warms up to see if I feel a surge of fluid once the thermostat opens up, look into a temp gauge, get a infrared thermometer along with feeling the heater lines (to your point). Could it be possible I'm just not working the engine hard enough? My test drives are on fairly flat ground...

 

[cruiserkev]

I had similar issues with my heater for a while and my 2F always seemed to run cool, even in the summer. Replacing the crusty old heater valve, a cooling system flush and installing a hotter thermostat worked wonders for my 40. Now I have great heat out of both heaters. Good luck!

 

[AntFarm]

Thank you, I did fill and submerse the core in CLR for a stint, cleaned out all the debris. I think my next steps are confirming Toyota sold me the correct thermostat, double check the fluid level, try that trick of holding the top radiator hose while it warms up to see if I feel a surge of fluid once the thermostat opens up, look into a temp gauge, get a infrared thermometer along with feeling the heater lines (to your point). Could it be possible I'm just not working the engine hard enough? My test drives are on fairly flat ground...

To answer your question on if yer working the engine hard enough...nope, it should come up to Normal Operating Temp (NOT) just idling in the driveway. Should take about 10 minutes give or take a few. In fact, once it gets up to NOT, the fan clutch should start to engage and you should be able to feel air being drawn in through the radiator by holding your hand 4-6 inches in FRONT of the radiator. I had a local radiator shop test and clean both my front heater core and rear heater core when I did my complete system refresh. Might be worthwhile for you to do this, once you figure out where your flow restriction is.

 

[igotta40]

If you find out you need a new heater core, let me know. I have one, good as new.

 

[Jeremyrig]

To answer your question on if yer working the engine hard enough...nope, it should come up to Normal Operating Temp (NOT) just idling in the driveway. Should take about 10 minutes give or take a few. In fact, once it gets up to NOT, the fan clutch should start to engage and you should be able to feel air being drawn in through the radiator by holding your hand 4-6 inches in FRONT of the radiator. I had a local radiator shop test and clean both my front heater core and rear heater core when I did my complete system refresh. Might be worthwhile for you to do this, once you figure out where your flow restriction is.

So a 74 has a fan clutch? Is it the viscous type? I feel like my fan is always spinning.

 

[Rocky_LC]

I believe my ‘74 originally came with the solid, 4 bladed orange fan. No fan clutch in that configuration....

 

[AntFarm]

My 9/74 has a fan clutch. It's a well preserved US spec truck, never been outside of western WA. I had no record from the PO of a swap at any point. I guess I had assumed that it came OEM, so I am not positive what was OEM for 74 US trucks. You can tell easily by just looking at your fan if an aluminum finned clutch is there. Note that a fan with a clutch DOES spin by visual check at all times. It just isn't spinning as fast as the crank until it locks up. However to your original point and question...when troubleshooting your cooling system, whether you have a clutch or not, it should still warm up properly and provide hot coolant to the heater through the firewall. Carry on and good luck.

 

[Jeremyrig]

My 9/74 has a fan clutch. It's a well preserved US spec truck, never been outside of western WA. I had no record from the PO of a swap at any point. I guess I had assumed that it came OEM, so I am not positive what was OEM for 74 US trucks. You can tell easily by just looking at your fan if an aluminum finned clutch is there. Note that a fan with a clutch DOES spin by visual check at all times. It just isn't spinning as fast as the crank until it locks up. However to your original point and question...when troubleshooting your cooling system, whether you have a clutch or not, it should still warm up properly and provide hot coolant to the heater through the firewall. Carry on and good luck.

Thanks much and I think this is getting close to the issue. How can I tell if the clutch is locked up from start/cold? That could explain the cooler temps if it's going full speed all the time, right? Do you know if it is a viscus coupling that's based on temp or based on a sensor or something else?

 

[Jeremyrig]

Thanks much and I think this is getting close to the issue. How can I tell if the clutch is locked up from start/cold? That could explain the cooler temps if it's going full speed all the time, right? Do you know if it is a viscus coupling that's based on temp or based on a sensor or something else?

My 74 is a January and here's some pictures - there's no finned type of clutch hub

 

[3_puppies]

Thanks much and I think this is getting close to the issue. How can I tell if the clutch is locked up from start/cold? That could explain the cooler temps if it's going full speed all the time, right? Do you know if it is a viscus coupling that's based on temp or based on a sensor or something else?

rigs that don't have a fan clutch, the fan spins all the time and move the same amount of air, that shouldn't be the problem. my 65 heats up just fine.

pic you just posted is a direct drive. You should change the 4 blade metal fan out for the plastic 6 blade version. the metal ones can and will break.

start back at square one and figure out what temp the engine is running at? either with a temp gun or a gauge.

 

[AntFarm]

Don't get too sidetracked by the fan clutch discussion. If you're not heating up the radiator or your heater core after a 30 minute drive, something else (or several somethings) is definitely wrong. Re-read the above posts. Some good advice there. One more thing...you might want to replace that belt soon

 

[Jeremyrig]

Thanks for all the input! One update is that I found that pressure is getting past the radiator cap into the overflow tank when I squeeze the top radiator hose. That's shouldn't happen unless there's enough pressure correct? Do you think a system without any pressure could be a cause? I'll pick up a new cap today

 

[Jeremyrig]

I think I found the smoking gun thanks to everyone’s help. in the process I have a much better functioning cooling system and i’m curios to drive once i’ve fixed it to see if it effects anything. The inside of the thermostat housing has some deep pitting on the surface that mates up to the top of the thermostat. They are big enough I could see how a lot of fluid could get by. I went ahead and plugged the main/top radiator hose, started her up and after about 5 minutes saw a big temp inincrease! Thanks again everyone!