Overheating

[Rumblefrog]

I have a 1984 FJ60 with 1HDT Diesel Engine and H55 transmission. When I first acquired the rig, it seemed to run hot; on a long hill it would go from 175 F to 215F. I replaced the thermostat with a new one (175F) and put in a new high capacity (375 HP capable) radiator and a 4000 CFM dual electric fan. This doesn't seem to have made much of a difference; on a long hill, it'll still go from 175F to 205F. I can't put any higher capacity radiator or fan in, so I'm kind of at a loss as to what's going on. I had this same radiator and fan in my 355 hp, V8 powered '82 Landcruiser, and it never overheated. The 1HDT only makes 167 h.p., so I'm a bit confused. P.S. - it doesn't use any coolant, so there's no head gasket issue.

 

[Gimme a 60]

Strange.


Leak down test is the best way to figure out if there is a blown HG or not.

 

[Eurasiaoverland]

Water pump?

 

[mudgudgeon]

Do you have boost and EGT gauges?
Are you using the stock, factory fitted turbo?

It would help a lot to know what your EGTs and boost PSI are when being pushed up a hill.
This will give an indication of how the fuel pump has been tuned.
If someone has added fuel, your combustion and exhaust temperatures could be too high ( too rich, burning excess fuel)


Diesels hate to be laboured. If you're pushing hard at low RPM in a high gear, you may be running high EGTs and introducing excessive heat into the head.
High load, low RPM equals high fuel delivery, low airflow. This means a relatively rich air fuel mixture and high combustion temperatures.

With the 1hd-t, if your RPM is dropping, and you have your foot planted, you really should be downshifting as RPM drop below 2500RP

Your engine will be happier in a lower gear and higher RPM. Peak power is at ~3600RPM. You have a manual gearbox, use it to keep the engine in its happy place.


Is running an engine driven fan an option?

Very few people are using electric fans on a 1hd-t.
Hard to match the capacity of an engine fan that still pulls air through the radiator at highway speeds.
A poorly performing engine can clutch can often be the cause of an overheating problem.

More information from you will get more useful answers

 

[Rumblefrog]

Do you have boost and EGT gauges?
Are you using the stock, factory fitted turbo?

It would help a lot to know what your EGTs and boost PSI are when being pushed up a hill.
This will give an indication of how the fuel pump has been tuned.
If someone has added fuel, your combustion and exhaust temperatures could be too high ( too rich, burning excess fuel)


Diesels hate to be laboured. If you're pushing hard at low RPM in a high gear, you may be running high EGTs and introducing excessive heat into the head.
High load, low RPM equals high fuel delivery, low airflow. This means a relatively rich air fuel mixture and high combustion temperatures.

With the 1hd-t, if your RPM is dropping, and you have your foot planted, you really should be downshifting as RPM drop below 2500RP

Your engine will be happier in a lower gear and higher RPM. Peak power is at ~3600RPM. You have a manual gearbox, use it to keep the engine in its happy place.


Is running an engine driven fan an option?

Very few people are using electric fans on a 1hd-t.
Hard to match the capacity of an engine fan that still pulls air through the radiator at highway speeds.
A poorly performing engine can clutch can often be the cause of an overheating problem.

More information from you will get more useful answers

I am the third owner, and, unfortunately, all the set-up details are unknown. Just assuming that turbo is stock. Don't have boost or EGT gauges. What is a "normal" temperature range for a 1HDT?

 

[mudgudgeon]

What is a "normal" temperature range for a 1HDT?

Coolant temp? 92⁰c I think is normal operating temp.

The problem with inheriting a modified vehicle is you'll never know what's been altered.

Toyota tuned the 1hd-t fairly conservatively. They can be tuned to produce a lot more power.
If someone has given it a poor tune, they can run hot under certain conditions.

I don't know how much you know about diesel engines?
Some tuning rules that apply to gas engines absolutely do not apply to diesels.
A rich tune in a diesel means hot combustion (opposite of gas engines).
High load, high fuel, low RPM conditions means HOT combustion.

Pulling up a mountain pass in high gear, and struggling to hold revs and high gear is an example of this high load, high fueling, low RPM.
Your engine will thank you for dropping to 4th, holding revs up, accepting the mountain has won, and pull the rest of the way 5-10-15mph slower.
Diesels generally run cool. They don't use a lot of fuel in most scenarios. Engine speed is controlled purely by how much fuel you put in. When under high load, that changes. You're putting in the maximum amount of fuel, so maximum heat from combustion.

In standard trim in an 80, the most likely cause of overheating is going to be poor engine fan performance. Or clogged radiator.
If these are good, then head gasket, or cracked head is an outside chance too.

If in your case, the radiator is significantly smaller in frontal area, than that isn't going to help. In that situation, a strong engine fan clutch hub will be more critical than ever.

EGT and boost gauges aren't essential in a stock standard configuration.
With a 30 year old engine, unknown history, in a retrofitted /engine swap scenario, EGT and boost gauges kind of do become essential, even if temporarily installed, to help you understand your engine's state of tune and a baseline for normal.
A rough tune can have a big impact on how much safety margin the engine has when being pushed

A few photos of the install, turbo, and injector pump could show any obvious changes from stock.

 

[Dougal]

Got a shroud on the radiator?

 

[Rumblefrog]

Coolant temp? 92⁰c I think is normal operating temp.

The problem with inheriting a modified vehicle is you'll never know what's been altered.

Toyota tuned the 1hd-t fairly conservatively. They can be tuned to produce a lot more power.
If someone has given it a poor tune, they can run hot under certain conditions.

I don't know how much you know about diesel engines?
Some tuning rules that apply to gas engines absolutely do not apply to diesels.
A rich tune in a diesel means hot combustion (opposite of gas engines).
High load, high fuel, low RPM conditions means HOT combustion.

Pulling up a mountain pass in high gear, and struggling to hold revs and high gear is an example of this high load, high fueling, low RPM.
Your engine will thank you for dropping to 4th, holding revs up, accepting the mountain has won, and pull the rest of the way 5-10-15mph slower.
Diesels generally run cool. They don't use a lot of fuel in most scenarios. Engine speed is controlled purely by how much fuel you put in. When under high load, that changes. You're putting in the maximum amount of fuel, so maximum heat from combustion.

In standard trim in an 80, the most likely cause of overheating is going to be poor engine fan performance. Or clogged radiator.
If these are good, then head gasket, or cracked head is an outside chance too.

If in your case, the radiator is significantly smaller in frontal area, than that isn't going to help. In that situation, a strong engine fan clutch hub will be more critical than ever.

EGT and boost gauges aren't essential in a stock standard configuration.
With a 30 year old engine, unknown history, in a retrofitted /engine swap scenario, EGT and boost gauges kind of do become essential, even if temporarily installed, to help you understand your engine's state of tune and a baseline for normal.
A rough tune can have a big impact on how much safety margin the engine has when being pushed

A few photos of the install, turbo, and injector pump could show any obvious changes from stock.

Thanks much for all the excellent information. I am pretty much diesel-ignorant. I've been impressed with how smooth this rig runs, and the mileage, compared to my V8, has been wonderful; I'm getting 23 on the highway (mountain passes included) and 19 in the city. I only get a little smoke when the engine is cold and taking off from a stop - never while cruising. I would assume that with a bad head gasket or cracked head, I should be losing coolant or getting gas bubbles in the coolant; neither is the case. I will confess that I've tried to pull up the long hills in fifth gear, and the rig seems to be capable of it (but just barely). I'll have to try dropping to fourth and living with the lower speed and see if that changes things.

 

[mudgudgeon]

I will confess that I've tried to pull up the long hills in fifth gear, and the rig seems to be capable of it (but just barely). I'll have to try dropping to fourth and living with the lower speed and see if that changes things.

Common error if you're not familiar with diesels.

1hd-t will happily rev at 3500-4000rpm all day. Your ears might might not be so happy.

it will be a lot happier doing 60mph in 4th with the engine revving at 3000rpm, holding speed and rpm, compared to 60mph, in 5th struggling to maintain 2500rpm.

Diesels don't like the latter. They are happier revving.


Ps, cracked head, or bad head gasket are unlikely, though possible.

Dougal raised a really good point about fan shrouds.
and also sealing between the radiator and the body so air can't bypass the radiator

 

[Rumblefrog]

Common error if you're not familiar with diesels.

1hd-t will happily rev at 3500-4000rpm all day. Your ears might might not be so happy.

it will be a lot happier doing 60mph in 4th with the engine revving at 3000rpm, holding speed and rpm, compared to 60mph, in 5th struggling to maintain 2500rpm.

Diesels don't like the latter. They are happier revving.


Ps, cracked head, or bad head gasket are unlikely, though possible.

Dougal raised a really good point about fan shrouds.
and also sealing between the radiator and the body so air can't bypass the radiator

Many thanks for the useful information. I've been driving it all wrong!

 

[Dougal]

A healthy 1HD won't overheat when pulling max torque sustained. It's not even 400Nm from 4.2 litres.

Show us some pics of the radiator fan setup.

 

[Squash]

205 is nothing.
Don't bat an eye over this.
Boiling temp of water is 212.
You are using coolant plus the system is pressurized so boiling temp is closer to 230 degrees.

 

[AussieHJCruza]

I wouldn't worry about 215F coolant temp...

 

[Rumblefrog]

I wouldn't worry about 215F coolant temp...

Thank you.

 

[4Ruster]

haha I start sweating when the temp goes above 195

 

[Rumblefrog]

haha I start sweating when the temp goes above 195

Yeah, I always have too.