FJ40 Radiator Extension (Reservoir Runs Out of H2O) (1 Viewer)

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Hi everyone. Just soliciting inputs in case you guys do experience the same thing. My FJ40's Radiator Extension (Reservoir) runs out of water after everytime I get to travel between 20 to 30 miles. There is no leak in both the Radiator nor in the Reservoir tanks. There are also no leak coming from the Radiator cap, Upper and Lower Hose and Water pump. However, at the middle of each transit i notice that the water inside the Reservoir is boiling. It is only when I make a full stop that I see water starts to emit thru the Reservoir cover. Though when I remove the Radiator cap when it is no longer hot, the Radiator is still full of water. I experience the same thing when i get to start the engine and have the engine run stationary from 5 to 10 mins. Hot water is also emiting from the Reservoir cap. What and where would you think the problem of my FJ's cooling system? I didn't experience overheating of the Radiator yet. Admittedly, under the hood is just so hot that I normally use rags to open it. Would appreciate any input. Thanks.
 
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It shouldn’t be using up coolant in the overflow… nor should it even need it. Boiling when you sit still for 5-10 minutes isn’t normal.

Have you done any recent work to it? Anything change?

What engine?
Have you burped the coolant system?
How old is the rad?

My initial thought is that your radiator cap is faulty. But that’s just a gut reaction.
 
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It shouldn’t be using up coolant in the overflow… nor should it even need it. Boiling when you sit still for 5-10 minutes isn’t normal.

Have you done any recent work to it? Anything change?

What engine?
Have you burped the coolant system?
How old is the rad?

My initial thought is that your radiator cap is faulty. But
Have you done any recent work to it? Anything change?

What engine?
Have you burped the coolant system?
How old is the rad?

My initial thought is that your radiator cap is faulty. But that’s just a gut reaction.

It shouldn’t be using up coolant in the overflow… nor should it even need it. Boiling when you sit still for 5-10 minutes isn’t normal.

Have you done any recent work to it? Anything change?

What engine?
Have you burped the coolant system?
How old is the rad?

My initial thought is that your radiator cap is faulty. But that’s just a gut reaction.
Thank you @bikersmurf .
Here's my answers to your questions:
Have you done any recent work to it? Anything change? - Yes, already overhauled the Rad. Though from the time I acquired my FJ40 2 years back the problem was already like this.

What engine? - Just an "F"
Have you burped the coolant system? - Drained many times the coolant.
How old is the rad? - I really don't have an idea. The FJ is just 2 years old with me.

My initial thought is that your radiator cap is faulty. But that’s just a gut reaction. - That's actually my first gut before and so i already replaced it but it did not solve the problem.
 
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Hi everyone. Just soliciting inputs in case you guys do experience the same thing. My FJ40's Radiator Extension (Reservoir) runs out of water after everytime I get to travel between 20 to 30 miles. There is no leak in both the Radiator nor in the Reservoir tanks. There are also no leak coming from the Radiator cap, Upper and Lower Hose and Water pump. However, at the middle of each transit i notice that the water inside the Reservoir is boiling. It is only when I make a full stop that I see water starts to emit thru the Reservoir cover. Though when I remove the Radiator cap when it is no longer hot, the Radiator is still full of water. I experience the same thing when i get to start the engine and have the engine run stationary from 5 to 10 mins. Hot water is also emiting from the Reservoir cap. What and where would you think the problem of my FJ's cooling system? I didn't experience overheating of the Radiator yet. Admittedly, under the hood is just so hot that I normally use rags to open it. Would appreciate any input. Thanks.
As mentioned, check the radiator cap. Have had similar problems on other cars and a new cap solved the issue.
 

flx

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Depends also of the year of your FJ40 and the reservoir you have.
Typically on my 74 there was no reservoir originally (started with the 2F I believed), obviously as it also expands if you fill full your radiator you will lose some coolant first time it's hot. I added a reservoir to stop pouring my coolant on the ground but to be able to fit it nicely and easily I put a small one. Basically it's slightly smaller that the potential coolant expansion between dead cold and maximum heat when hammering it, in result the reservoir tends to run at the minimum but the radiator keeps more water inside than without the reservoir.
 
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CBB0090C-3DFC-4CD6-8BEF-CB7D822A7BB4.jpeg

it sounds like you’ve started on the right path.

Are you running a 50/50 coolant mix?

What does the temperature gauge show?

Thermostat would be next on my list… and be sure it matches OEM design and use all gaskets/seals.
 
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If it's a F, it did not had an overflow reservoir from stock so a picture of the setup is much needed.
Thanks @flx . Am not aware of the F model that didn't have an overflow reservoir then. Will try to find out more about the details on that. Thankd again.
 
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View attachment 2735398
it sounds like you’ve started on the right path.

Are you running a 50/50 coolant mix?

What does the temperature gauge show?

Thermostat would be next on my list… and be sure it matches OEM design and use all gaskets/seals.
Thanks again @bikersmurf . Am using a ready-mixed coolant. The temperature gauge remains at the normal level especially when my 40 is running. It only goes up when am stocked in the traffic for 10 to 20 mins. Will try to replace the thermostat. Hopefully, this will solve the problem. Appreciate your inputs brother.
 
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Depends also of the year of your FJ40 and the reservoir you have.
Typically on my 74 there was no reservoir originally (started with the 2F I believed), obviously as it also expands if you fill full your radiator you will lose some coolant first time it's hot. I added a reservoir to stop pouring my coolant on the ground but to be able to fit it nicely and easily I put a small one. Basically it's slightly smaller that the potential coolant expansion between dead cold and maximum heat when hammering it, in result the reservoir tends to run at the minimum but the radiator keeps more water inside than without the reservoir.
Well noted @flx. Thank you so much.
 

fjc-man

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When did Toyota start installing viscous fan clutch units on these motors? Did it start with the 2F? Well anyway, if you have one maybe it’s not engaging like it should, causing it to run hotter, especially when not moving.
 
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I had the same symptoms and it ended up being a cracked head. Truly hope this isn't the case with yours. Mine had a hairline crack where miniscule amounts of coolant leaked into piston #2 and exited through the tailpipe. Cooling system was also getting pressurized from the compression stroke too causing bloated hoses. There is a test you can do on your coolant to see if exhaust gasses are getting in there.
 

73FJ40

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@FES74

OEM coolant reservoirs started in January 1975. You can see from the illustration, below, no reservoir was in F engine FJ40's from 1969 through the end of 1974.

1626740870009.png


You really need to post some pictures of the piping arrangement to your reservoir. If there is boiling water leaving the radiator and entering your reservoir, the coolant in the reservoir should act to quench the hot radiator water, collect it, and then let the coolant flow back into the radiator when the engine cools off, and the coolant contracts.

Note that is there is air in the engine cooling system, the heated air will force a lot more coolant out of the radiator than just expanding coolant.

The original radiator cap (non recovery system) is typically a single seal cap, whereas a recovery system cap is a double seal cap. Make certain you have the correct one.
 
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I had the same symptoms and it ended up being a cracked head. Truly hope this isn't the case with yours. Mine had a hairline crack where miniscule amounts of coolant leaked into piston #2 and exited through the tailpipe. Cooling system was also getting pressurized from the compression stroke too causing bloated hoses. There is a test you can do on your coolant to see if exhaust gasses are getting in there.
Thanks @cruiserkev . I just hope it is not a case of cracked head. Though this is a very good input. Will do a thorough evaluation of the engine. Btw, would you mind sharing what type of testing or how that testing is called to determine if gasses are getting in the coolant? Thought of relaying this to my mechanic. Thanks again.
 
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Thanks @cruiserkev . I just hope it is not a case of cracked head. Though this is a very good input. Will do a thorough evaluation of the engine. Btw, would you mind sharing what type of testing or how that testing is called to determine if gasses are getting in the coolant? Thought of relaying this to my mechanic. Thanks again.
My mechanic let me borrow an older device that attaches to the radiator in place of the cap. You then run the engine and it tells you if exhaust gasses are present. Sure wish I knew what it was called but this was several years ago. Good luck!
 
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When did Toyota start installing viscous fan clutch units on these motors? Did it start with the 2F? Well anyway, if you have one maybe it’s not engaging like it should, causing it to run hotter, especially when not moving.
Thanks @fjc-man . Am not sure if mine has a viscous fan clutch. What i have is a fan that's connected directly to the engine. The fan continues to engage without stopping so long as the engine is running. But I'll have it checked just the same. Thanks
 
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*note The viscous fans still spin even when cool, but not aggressively. If you do have a viscous fan it will roar noticeably when hot.
Properly working viscous fans are very important. The truck WILL overheat if it's not working properly.
 

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