intercooler causing overheating

Submitted: Friday, Feb 07, 2014 at 11:52
ThreadID: 106125 Views:8735 Replies:7 FollowUps:1
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Hi all,

I recently had the engine in my 1HZ troopy rebuilt. It had the DTS turbo kit fitted when I bought it. according to the bloke who rebuilt it and the diesel pump the fuel mixture was to rich which caused excessive heat and cracks to occur in the cylinder head (it looked like it was leaking from around the gasket).
I've since got it back and and fitted a top mount intercooler to cool the pressurised air from the turbo.
We did the 1000km run in and brought it back for the initial service. All looked fine so they readjusted the fuel mixture for a little more power. I have also fitted a digital pyrometer, they mentioned to watch it under heavy load and to not exceed 500 degrees.

Over the Christmas period we took it through the snowy mountains for a little explore. Climbing up mt buller it became very hot on the coolant temp gauge although the exhaust temp did not exceed more than 430 degrees.
this happened again on another big hill climb. On both occasions we did not exceed more than 5psi boost and the kept the engine revs well bellow 3000 rpm.
Apart from that the coolant temp was fine even on a few other big climbs.

We brought the car back to them shortly after to get it checked out. Unfortunately at the time they were to busy to check it properly and asked if we could bring it back.

He did however notice the intercooler and mentioned that this is what could be causing the problem. Something along the lines of the cooler, denser air containing more oxygen therefore increasing the combustion temp.
He mentioned some of the factory intercooled 1HD-FTE motors having the same problem since new and that Toyota had to redesign the system.

has anyone heard of a similar theory? He seems like a straight shooter, I've just never heard of a cooler causing overheating...

Also does 500 degrees sound about right for exhaust temp limits?

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Reply By: Ross M - Friday, Feb 07, 2014 at 13:59

Friday, Feb 07, 2014 at 13:59
By your EGT gauge it looks like the exhaust temp isn't getting too hot so OK.
Although with an intercooler and fuel adjusted correctly it won't get too hot but the quantity of exhaust gas can be more volume.

The water temp is a result of heat volume input to the water and with a turbo there will be more heat volume both in the exhaust and delivered to the water of the cooling system.
Therefore, the cooling system has to be able to, cater for and dissipate, more heat than before the turbo was fitted.

The OE cooling system relies on the viscous fan clutch to drive the fan and cool the radiator by the airflow through the core. If the fan clutch isn't in top health and not driviing sufficiently then the overall cooling rate will be reduced.

The airflow into the radiator and through the rad core and out under the vehicle is a carefully designed system so it will clear it through.
Now you have added a top mount intercooler it, to perform, will have to have airflow into and through it. That means it will now begin to pressurize the engine bay behind the radiator and so fan flow through the radiator will/may be reduced.
That can result in less heat removal from the radiator water and so it will then run hotter especially in slower running as the forward motion of the vehicle is reduced and it doesn't vacuum the air out of the engine bay as fast as higher speed does.

Get a tail wind/breeze and the heat can well up and only what the fan can pass is doing the cooling. Less flow into/through the IC will mean it won't be very effective at in that situation and so intake temp will not be as cooled as it would like.

A possible solution is to fit two fans, one either side of the engine and down near the chassis rails so they can suck and blast hot air down and out of the bay when conditions are less favourable. ie clears the engine bay so the rad fan can do it's job.

If it isn't cooling well, place a piece of wool or cotton on the IC intake and see if gets blown outwards at slow speed when fan is running/everything HOT. If so, the rad heat is going backward through the IC and heating it.
AnswerID: 525925

Reply By: Member - Noel K (NT) - Friday, Feb 07, 2014 at 15:17

Friday, Feb 07, 2014 at 15:17
G"day rb30e,

I think Ross M is on to it with the air cooling. I have recently installed a turbo and top mounted intercooler on my 105 Series, this intercooler has a large fan mounted under it that helps draw air through a bonnet scoop.
I also fitted a 3 inch exhaust system which also helps get the hot gas out.
The highest my EGT has been is 450 degrees, passing a road train, while I was towing a 1.5 tonne camper. As soon as I backed off the ETG dropped to its normal 320 degrees. The factory water temp gauge stayed as per normal.
Yes 500 degrees is the deadline, aluminium melts at about 600 degrees. Personally I would be backing off before 500 degrees.
I have also fitted a Mann-Pro oil catch can to keep the oil blow-by residue out of the intercooler so that it does not become blocked with gunk.
All in all, I am very happy with the set up especially in our climate up here in the NT.


Noel K.
AnswerID: 525929

Reply By: kiwicol - Friday, Feb 07, 2014 at 16:03

Friday, Feb 07, 2014 at 16:03
If you have rebuilt the engine, the radiator should be either replaced or pulled apart and cleaned.
Most engine rebuilders will not guarantee the engine if the rad. is not serviced.
While doing the rad replace or service the fan clutch.

AnswerID: 525931

Reply By: Ozhumvee - Friday, Feb 07, 2014 at 16:41

Friday, Feb 07, 2014 at 16:41
Also be aware that the 70 series has had poor airflow through the engine bay since day one right back in 1985. The original 2H would overheat at the drop of a hat especially if spotties etc restricted airflow through the radiator. The 1HZ was better mainly due to a higher coolant capacity, they all also cooked starting batteries due to excessive underbonnet temps, Toyota even encased the battery in a separate box that had an external vent on some models.
One of the early turbo fitters (might have been Safari?) put a 70 in a wind tunnel and they found that air flow was non existant at some highway speed and crosswind conditions.
You should probably add more silicone fluid to your fan clutch hub (available from Toyota as a spare part) before doing anything else as they get tired with age. My experience with aftermarket ones was never good, was just easier and cheaper to top up the original with extra fluid.
Adding the intercooler on top wouldn't help the airflow through the radiator at all.
Another trick to try re the viscous fan hub is to wrap a piece of rope between the hub and the pulley so the fan is locked on and take it for a drive. It will make a lot more noise and you may even notice a loss of power as it takes quite a bit to drive the fan.
AnswerID: 525933

Reply By: pop2jocem - Friday, Feb 07, 2014 at 20:48

Friday, Feb 07, 2014 at 20:48
Another problem with the earlier 70's was the frontal area and therefor the width of radiator that could be fitted. A wider or longer radiator is much more efficient than an extra core or 2. All of the above is good advice and things to check. If all else fails remove the air con evaporator from in front of the radiator and have an air con specialist fit one of them Red Dot roof mounted jobbies that have their own cooling fan.
Worked for me when I fitted a 1HD-FT engine to my old girl. Runs the standard radiator and pulls my caravan in 40 degree heat with air con going flat out no dramas.
Also extra boost actually cools the engine internals and turbo as long as the fuel volume isn't increased as well. Not too much though 8 or 9 lbs should be plenty.

AnswerID: 525947

Reply By: rb30e - Saturday, Feb 08, 2014 at 17:14

Saturday, Feb 08, 2014 at 17:14
Thanks everyone for the helpful information, always a wealth of knowledge on exploroz.

Ross M that's an interesting point that you make about the airflow that is created by fitting a bonnet scoop pressurising the engine bay and effecting the rate at which the air flows through the radiator. That's not something I would have thought of.
I fitted the HPD cooler which has a 9" thermo fan fitted underneath, I have this fan controlled by my Pyrometer which has a relay that can be programmed with a cut in and cut out temp. I have set it to cut in when the exhaust temp reaches 200 degrees and cut out at 150.

My troopy is pretty unique in the fact that it has an 80 series auto fitted. I bought it like this because im paraplegic and can not drive manual anymore.

because of this I've had to fit some auto trans coolers to the front. It was previously fitted to the bullbar where the winch sits, they cut out a big slot and fit a grill for airflow. I've since fitted a winch to the bar after welding and reinforcing it and relocated the cooler to in front of the A/C condenser. Because of the change of airflow I fit a secondary trans cooler which is long and thin behind the panel with the three slots under the grill, this is still in front of the radiator. I've also got two light force 170 striker spotties fitted to the bar which is also in front of the radiator which cant help for airflow.
That being said, with the trans coolers, spotties and condenser this is going to be causing a big disruption to the airflow through the radiator. The previous owner has replaced the standard radaitor with an aftermarket alloy one with extra cores, this was done shortly before i purchased it, the coolant looked nice and green so I figured there was no need to replace or service it.

Once I get the car checked out by the engine shop to confirm there is no problem with the cooling system (pressure test, gas analysis, check the thermostat) I'll start looking at ways to improve the airflow, repositiong the spotties and trans coolers would be a good start.

I was wondering about the viscous clutch too as the car has 335 000km, I'm not sure if its the original one thats never been serviced or not. I didn't realise you can buy the viscous silicone liquid, thats handy as I think the price of a genuine clutch is around the $300 mark.

One more thing I was going to do is replace the radiator cap, this could be a cheap and easy fix.

AnswerID: 525996

Reply By: Dust-Devil - Thursday, Feb 13, 2014 at 12:01

Thursday, Feb 13, 2014 at 12:01

I have been through all of the above plus blowing the engine up at 116.000kms.

However I will admit to doing horrific things to that 1HZ that contributed greatly to the destruction of same.

Cooling (major problems) was the other factor in the aforementioned catastrophic failure equation.

It now runs exceptionally well and extra extra cool.

The solution/s etc to get to where it is at now, are too numerous and involved to elucidate here, so if you wish, you can contact me on 0430 468 480 and I will be only too happy to discuss same.


AnswerID: 526347

Follow Up By: rb30e - Friday, Feb 14, 2014 at 11:22

Friday, Feb 14, 2014 at 11:22
Cool, will do I'm just in nepal at the moment will be back at the end of the month. I'll give you a call then. Thanks mate
FollowupID: 808631

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