80 series HZJ80 1HZ Overheating

Submitted: Wednesday, Jul 14, 2010 at 21:42
ThreadID: 80086 Views:16150 Replies:11 FollowUps:7
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Hi fellas,

I have the diesel HZJ80 1993 model and yup, she's a overheating. Was all fine until I started towing my boat (trailer + boat = about 700kg) when after about 80 km/h the temperature would rise and eventually lead to water boiling out of the overflow bottle.
Replaced the thermostat with genuine Toyota, new top and bottom radiator hoses, had the radiator flushed out by a radiator place, replaced the fan clutch and I drained the oil out of the new clutch and put in the Toyota silicone oil, new coolant, new fan belts.
Now its progressed to overheating when I am driving the car alone over 80 km/h without the trailer on.
Any thoughts on what it could be next? No leaking from the water pump but I'm thinking there next ?
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Reply By: Member - Nick (TAS) - Wednesday, Jul 14, 2010 at 22:03

Wednesday, Jul 14, 2010 at 22:03
Any black smoke??
Could be the fuel system over fuelling.
Radiator cap?
Get a test done for Co2 in the coolant.Could be a cracked head.
AnswerID: 424065

Follow Up By: 80seriescruiser - Wednesday, Jul 14, 2010 at 22:14

Wednesday, Jul 14, 2010 at 22:14
Yup put on a new radiator cap. No black smoke coming out the back, no loss of power either when I drive it - symptoms I presume of a head gasket.
FollowupID: 694489

Reply By: Malleerv - Wednesday, Jul 14, 2010 at 22:12

Wednesday, Jul 14, 2010 at 22:12
Could be a slipping impeller in you water pump but it sounds more like a blown head gasket or cracked head to me.
Start it with the radiator cap off and watch it as it heats up idling or just above idle. Look for continuous bubbles of froth forming in the filler neck of the radiator.
If you see either its time to pull the head off.

Cheers Matt
AnswerID: 424067

Follow Up By: Member - Ian H (NSW) - Wednesday, Jul 14, 2010 at 22:15

Wednesday, Jul 14, 2010 at 22:15
Yes, this is my guess from here. Good luck.
FollowupID: 694490

Reply By: Joe n Mel - Wednesday, Jul 14, 2010 at 22:24

Wednesday, Jul 14, 2010 at 22:24
sounds a lot like mine, started heading up from Katanning, fine down low speeds and slowly worse as the days went by, started to get hot at 110 in cold RAIN ..............
1st did thermostat in perth, it was not opening fully, better but still getting hot.. (June)
2nd fitted sh radiator from wreckers in Perth, helped heaps, made it to Tom Price... Got hotter at Broome .....
Long story cut short.. Broome, Darwin, Alice Springs and halfway up the Tanimi for 3 months, was summer by then and all started getting hot again...soooo..
Got brand new radiator and fitted, new thermostat (again) and complete set of hoses and belts and re-oiled up the fan clutch and fitted watch-dog.... went heaps better but could not handle the REALLY hot days with A/c ....
Travelled back up to Darwin and back down to Booraloola and got a brand new fan clutch and it is as cool as a cucumber now, loaded, ac, 3 kids and camper ....
So from my experiance and all other posts i have read..... get a brand new radiator (exactly the same "original"), new t/stat, new hoses, new belts, new coolant, and finally buy a NEW and TOYOTA original fan hub, dont touch it just install as is and providing you dont have a cracked head you will have no further problems, if the head is cracked you will still need to do all above anyway if you want it to last....
Cheers matey and good luck......
AnswerID: 424069

Follow Up By: 80seriescruiser - Wednesday, Jul 14, 2010 at 22:46

Wednesday, Jul 14, 2010 at 22:46
Going with a new water pump tomorrow. I've done 200,000k in the beast and not touched the water pump so its due anyway. Bit of a job pulling off the timing belt. Did the water pump in a 40 series about 5 years ago, a 5 min job, didnt have to touch anything, pull off bolt on new one. Anyway, I will use a genuine water pump and if that doesnt work, hmmm, I'll have to think some more . . . .
FollowupID: 694494

Follow Up By: mechpete - Thursday, Jul 15, 2010 at 16:04

Thursday, Jul 15, 2010 at 16:04
in all my 40 yrs in the mechanical trade ,I have never seen a water pump
with a slipping impeller or the pump itself causing an overheating issue
other than a leaking sealing causing loss of coolant .
, yes fan clutches are a big problem on toyotas bye only genuine .
cheers Pete
FollowupID: 694539

Reply By: Member - Phil G (SA) - Wednesday, Jul 14, 2010 at 22:46

Wednesday, Jul 14, 2010 at 22:46
#1 You need the radiator place to remove the top tank and have the radiator "rodded" - flushing usually doesn't do much. This is still the most common cause of overheating, and from what you say, it hasn't been done.

#2 have you cleaned out the air cond condensor in front of the radiator?

I'd also be fitting a digital temp gauge/alarm, like the TM2. Toyota temp gauges are poorly calibrated - they don't rise until the temp gets above 95 degrees.
AnswerID: 424073

Follow Up By: steve21 - Thursday, Jul 15, 2010 at 08:15

Thursday, Jul 15, 2010 at 08:15
i would say Phil has hit the nail, i had same problem. you need the rad rodded. good luck steve
FollowupID: 694499

Follow Up By: Member - Cash (WA) - Thursday, Jul 15, 2010 at 16:29

Thursday, Jul 15, 2010 at 16:29
I second Phil on this one. Spent the dollars on all that has been mentioned only to have the same problem occur again. I had had the radiator 'serviced' but that doesn't include rodding. Had the radiator 'rodded' and bingo, problem solved - that's over 12 months ago now! My unit sits between adventures and so flushing the radiator core doesn't always remove the finer and more compact sediment.
FollowupID: 694542

Reply By: Member - Serendipity(WA) - Thursday, Jul 15, 2010 at 00:53

Thursday, Jul 15, 2010 at 00:53
After checking the usual cuprits for over heating - and it looks like you are onto these ones - the motor can over heat for a number of reasons already listed.

Usual cuprits are the radiator flow, colapsed hoses, poor water pump, blocked water jackets on motor. But usually there are tell tale signs of these and they build up with regular overheating problems.

Yours sounds much like an issue I had with my HJ75. Ran fine until one day a cop pulled me over and said I was blowing white smoke after taking off at the lights. This I had never noticed before and had no explanation at the time. Motor seemed to run alright.

That weekend we packed up the camper for a weekend away. Barely got 3 km down the freeway and the car over heated. Strange. Pulled over and let it cool off a bit at idle and took off again at 100km/h and bingo -over heated again.

Result - Mechanic found I had blown the rings in one piston. $5000 later I had a complete rebuilt motor. Very hard to deal with that cost at the time but with a blown motor a car is really worthless.

Looking back now I had the option of putting a turbo diesel motor in rather than the rebuild for a cost of $11 000 fitted. Should have done that but just struggled with that kind of money outlay.

Years later I spent $8000 and put the turbo diesel in - and what a difference. Just a world of difference and wished I had spent the money all those years earlier and had been driving around at real speed with better economy. So for 10 years drove with naturally aspirated and then 5 years with turbo in same car. Hind sight is a fickle thing.


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AnswerID: 424080

Reply By: Member - Amy G (QLD) - Thursday, Jul 15, 2010 at 07:57

Thursday, Jul 15, 2010 at 07:57
I second the radiator rodding- the fins fill up with muck over time and flushing it out doesn't remove it. My HZJ80 overheated under load when I bought it and this fixed it up (along with a new thermostat, which you've already done). It's not much money so definitely worth a go.
AnswerID: 424087

Reply By: Hairs & Fysh - Thursday, Jul 15, 2010 at 08:19

Thursday, Jul 15, 2010 at 08:19
Stat with replacing the Silicone grease in the fan clutch, You can buy this from you local Toyota dealer, about $70 I think, It is a common problem with the early 80's.
You mentioned symptoms of a head gasket? Is your coolant system pressurizing more than normal?
Is there fine bubbles in the top tank of the radiator with the cap off? are you losing coolant? Because these are the usual signs of a warped head or head gasket problem.
I'd try the fan clutch first.
Hope you find it.

AnswerID: 424089

Reply By: Member No 1- Thursday, Jul 15, 2010 at 09:08

Thursday, Jul 15, 2010 at 09:08
I'm with Amy and Phil above

I had a radiator problem on an old 100 series just out of warranty
....found the core blocked with crap...err like a allot scale.....replaced and all ok

the coolant was supposedly replaced at its prescribed time ...what actually was this...they (the mob with a goanna as their logo) replaced coolant with a different type, without correctly flushing old stuff out which when combined reacted attacking alloy radiator...god only knows what it did to the engine side of it....it is a common problem going by the mob who replaced the radiator...i took up the issue, got some info from them but they then went very quiet and refused to talk when they realised where I was going

anyway check the PH of your coolant
AnswerID: 424096

Follow Up By: Member - Phil G (SA) - Thursday, Jul 15, 2010 at 11:49

Thursday, Jul 15, 2010 at 11:49
I'm with MN1 too :-)
Mixing coolants causes the tubes to block. The way to stop that is to only use teh genuine Toyota coolant for the life of the vehicle. It really annoys me when friends pay good money for vehicle servicing and the idiots put in some green rubbish into their cooling systems. I have a good friend who owns a number of radiator repair shops in Adelaide and he says he sees this all the time.
FollowupID: 694516

Reply By: Therifleman - Thursday, Jul 15, 2010 at 12:39

Thursday, Jul 15, 2010 at 12:39
Good Day,some years ago my 80 series was overheating according to the temp. gauge when all else was in order.My mechanic put a temporary,properly calibrated gauge on it & took it for a good run(Mt.Colah to Gosford),all was good on the temporary gauge but the vehicle one was still showing it was overheating.Well there is a problem with the 80 series temp. gauge & the fuel gauge.It can only be rectified by replacing the fuel gauge,this was done & no more troubles.It may seem far fetched but if you talk to a GOOD!! auto.electrician he may be able to put you on the right track.
AnswerID: 424111

Reply By: Member - Pat (VIC) - Thursday, Jul 15, 2010 at 13:31

Thursday, Jul 15, 2010 at 13:31
when was the last time the shims done on the valves, as they wear the gap gets smaller restricting the flow of the gasses causing the engine to run hotter.
I know you say it still drivers the same i thought the same until i got mine done.
Worth a try if all else fails.
AnswerID: 424114

Reply By: fisho64 - Thursday, Jul 15, 2010 at 15:15

Thursday, Jul 15, 2010 at 15:15
1st step-pressure test the cooling system and then you should see if there is a blown gasket, cracked head. Also as said-CO2 test.

But maybe if your not sure what to look for get a mechanic to at least diagnose it, probably save you mucho folding?
AnswerID: 424125

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