Engine cooling

Submitted: Monday, Sep 03, 2012 at 21:54
ThreadID: 97818 Views:4329 Replies:10 FollowUps:2
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Hi all

I've got a 85 model HJ 75 Troopy with a 05 1HDFTE conversion. I'm worried about keeping the big donk cool. I could only fit a smaller gel fan because of space restrictions In the engine bay.
This is fine in Sydney but the temperater needle has lifted once before on the beach. I was able to pull straight over but now I'm ummm a little concerned.

I've lookied into other ways if keeping it cool ie oil coolers and water jets etc.

I'm by no means a mechanic but I love this truck and don't want to cop 10k for a new engine.

Any thoughts would be really appreciated...
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Reply By: pop2jocem - Monday, Sep 03, 2012 at 23:45

Monday, Sep 03, 2012 at 23:45
Hi james,

Not sure how far you are intending to go but here is what I have done.

I have a '91 HZJ 75 to which I have fitted a 1HD-FT. I noticed that towing a 22' caravan in ambients any higher than the mid 30's would cause the original temp gauge to climb alarmingly even without the use of the air con and this was with the old 1HZ slugger fitted. When I did the conversion I had the radiator tanks removed and the core "rodded', fitted a new thermostat and replaced the fan clutch assembly. In addition to this I removed the standard air con condenser that lived in front of the radiator and had a roof mounted unit fitted. I also replaced the standard water temp and oil pressure gauges with VDO units as IMHO the standard Toyota gauges are little better than idiot lights to accurately monitor these functions. So far the temp gauge climbs to about 85 degrees C and sits there within 5 degrees regardless of ambient temps, gradients and air con on or off.
Cost a few bucks to get all this done but I would rather do all this and not have to rebuild a toasted engine and then still have to do some mods so that it did not recur.

AnswerID: 494202

Reply By: Ozhumvee - Tuesday, Sep 04, 2012 at 01:46

Tuesday, Sep 04, 2012 at 01:46
As Pop and I discovered the 1HZ will run hot in a 75 let alone a turbo engine.
Back when the 75's were new one of the aftermarket turbo companies put one in a wind tunnel and discovered that due to the body shape, grille opening etc there was virtually no airflow through the engine bay at 100kph so the cooling system has to be in top notch condition and with engine swaps the only real way to improve it is to do what Pop has done and get rid of the a/c condenser from in front of the radiator. Nothing in front of the grille either.
AnswerID: 494204

Reply By: Member - Bucky - Tuesday, Sep 04, 2012 at 04:22

Tuesday, Sep 04, 2012 at 04:22
james 75

Have a good look at your radiator's capacity.
I could be wrong, but my understanding of engine cooling is that, if the motor and radiator capacity is 30 lts coolant, then it will require 30 lts of coolant, and not 20 or 25,lts, if you put that motor into a different body.

The next thing to look at is the ability of the fan system, and body shape to efficiently cool the motor, or remove the heat generated bu the motor.
ie cowling, and fan and general air flow thru the engine bay.

There is no use putting a huge radiator into an inefficient enviroment, as this may only delay overheating by a few minutes.

Click here, they may help

You could also try ask the some race car drivers, I am sure they are familiar with this problem


AnswerID: 494206

Reply By: Rockape - Tuesday, Sep 04, 2012 at 04:58

Tuesday, Sep 04, 2012 at 04:58
Mate I have a 6.5l chev diesel in a 89 troopy.
I fitted a genuine radiator out of the 78 series turbo cruiser with a custom made shroud around the fan and run the genuine Tojo fan hub.

Radiator Part No. 1640017360

The radiator is longer than the original by about 50mm so you have to get the later model bottom radiator guard which bolts straight on.

This combination has never seen the engine overheat at anytime and that includes towing over more than 100,000 K's.

I would recommend fitting a aftermarket temp gauge as the Tojo ones are dampened to much and don't give a true indication of the engine temperature.

AnswerID: 494207

Reply By: woozle - Tuesday, Sep 04, 2012 at 09:30

Tuesday, Sep 04, 2012 at 09:30
I had the same problem with my troopy after fitting the after market turbo first thing is replace the Toyo temp gauge as stated they are useless then I fitted an all alloy radiator from PWR and no more overheating even in NT towing a very heavy trailer with a boat on top
AnswerID: 494217

Reply By: Andrew - Tuesday, Sep 04, 2012 at 11:32

Tuesday, Sep 04, 2012 at 11:32
Hi James

This is a bit of a collection of information based on experience and suggestions from this forum. Thought it might help to put it all in one place.

Need sufficient cooling fluid to absorb the heat and transfer it to the radiator.
As suggested go with the replacement engine capacity as a guide.

Use the correct coolant and change it when recommended. It makes sure the innards remain clean so that heat transfers to the cooling fluid effectively. Scale and dirt in the system can dramatically reduce heat transfer.

Water pump impellers need to be in good condition but this is usually protected by the correct coolant.

Drive belts correctly tensioned and not hardened and cracked so there is no slippage.

The thermostat needs to be in good condition and fitted.

No bent or missing fan blades.

Best quality radiator you can fit in the hole.
Seal the gaps around the radiator. You want the air to flow through it not around it.

Close fitting fan shroud to maximize the efficiency of the fan and assist airflow through radiator. Especially helps for low speed operations.

Don’t block the radiator air flow. Mounting driving lights etc.... far enough away so that the air can flow around them. If using mesh for grass seeds or spinifex you need to make sure there is sufficient open area in the mesh to allow sufficient air through, so wrapping the front of the bull bar is much better than a simple shield in front of the radiator.

Don’t block the air that’s trying to get out of the engine bay. Air won’t flow through the radiator if the air already in the engine bay is trapped by shields and accessories.

If your new engine, turbo, air cleaner, piping causes blockage then consider extra vents out the side of the engine bay to relieve the pressure. Don’t put them in the top of the bonnet as this is a high pressure area that will try to flow air in instead of out.

If that hasn’t given you a safety margin then consider fitting an oil cooler. This not only removes heat but also reduces the load on the cooling system.

Don’t mount an oil cooler in front of the radiator unless there is absolutely nowhere else to put it. You don’t want to feed hot air to the radiator.
You can mount them at any angle to fit a gap as long as there is air flow through it. This can be resolved with duct work. For low speed work it may need to be in the engine fans’ air flow or perhaps have its own electric fan.

As suggested, moving the air conditioning condenser to the roof removes an air restrictor and a heat source.

General comments.

In a vehicle that originally did not have a heating problem:

Replace the thermostat.

Test and / or replace the radiator cap.

Check that the transfer tube between the radiator tank and the remote filler container is clear and the container outlet is not clogged. If this bit doesn’t work properly you end up with air instead of coolant in the radiator which reduces its efficiency.

Overheating at low speed only, is generally related to a lack of airflow, so fans, drive belts, missing shrouds or things that block air like bonnet insulation falling down are the sorts of things to check out.

Overheating at high speed only is usually a heat transference issue most likely an internally blocked radiator.

Spongy radiator hoses can collapse and restrict coolant flow.

In a vehicle that has always run hot, if when the heater is turned on with the fan on high the engine temp comes down, then there is probably insufficient cooling capacity in the standard system and aftermarket fixes are needed.


AnswerID: 494226

Follow Up By: Member - Serendipity(WA) - Tuesday, Sep 04, 2012 at 13:09

Tuesday, Sep 04, 2012 at 13:09
Wow Andrew has summed it up perfectly.

I was going to add to other great suggestions and then read what Andrew wrote and thought is there anything left.

Well - only that I had a HJ75 in Darwin and put in the 12H-T turbo motor and yes it ran a bit hotter. My solution was to put in a high core fin radiator - same size as the original but with more cooling fins down the cores. This sure dropped the temp by a measurable amount.

Seems all the people have given lots of good suggestions.

Hope my bit helps, cheers


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FollowupID: 769859

Reply By: james 75- Tuesday, Sep 04, 2012 at 19:02

Tuesday, Sep 04, 2012 at 19:02
Hi all

Just got back on the net and saw all the feedback, thanks to all. I will look at these options, I will defiantly get better gauges and move the aircon compressor, I will get onto my mechanic re the oil cooler and look at the air flow through the engine bay.

I will look possibly fitting a pn exhaust temp gauge to better monitor the heat.

Thanks again.
AnswerID: 494242

Reply By: james 75- Tuesday, Sep 04, 2012 at 19:03

Tuesday, Sep 04, 2012 at 19:03
Special thanks to A you summed it up perfectly your a legend dude
AnswerID: 494243

Follow Up By: mick v1 - Tuesday, Sep 04, 2012 at 19:27

Tuesday, Sep 04, 2012 at 19:27
father in law put a turbo on an 80's and it would get hot when towing, cleaned the radiator replaced fan bearings and it still got hot. Put 3" exhaust on and never got hot again,
FollowupID: 769892

Reply By: Member - Walter H (WA) - Tuesday, Sep 04, 2012 at 21:34

Tuesday, Sep 04, 2012 at 21:34
G'day James,I have a 78 series Troopy which also had engine temps spike after fitting a Turbo and front mount intercooler,so i had the radiator fitted with what's called a tripple bypass baffle system which dropped the temp by 8 degrees as i had fitted a engine watch dog, but i also took a reading of the engine bay as the high temps wasn't helping and were killing my batteries so i also fitted a air scoop to the bonnet to get more air in to which worked a treat and lowered my engine bay temps by 12 degrees and since covered 30000 k's with no issues.
AnswerID: 494263

Reply By: james 75- Tuesday, Sep 04, 2012 at 21:35

Tuesday, Sep 04, 2012 at 21:35
Mm interesting, my trucks got a 3in mandrel bent exhaust, I can see how it would help.
AnswerID: 494264

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