TD Prado overheats

Submitted: Thursday, May 17, 2007 at 13:10
ThreadID: 45577 Views:4770 Replies:6 FollowUps:10
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My 2001 Prado 1KZ TD auto got very hot very quick last night. Now blows pretty bubbles through the radiator. I have heard of a tendency for the head to crack - can anyone confirm this and how widespread a problem it may be?

Hopefully it's just the gasket and I have avoided any further damage by shutting it down as soon as the temp shot up. 8~(
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Reply By: jeffwa - Thursday, May 17, 2007 at 13:35

Thursday, May 17, 2007 at 13:35
Oopsy. They do have an alloy head so getting them hot is not great and can easily cause the head to crack.

The problem is that your temperature guage probabaly didn't even start moving from half way until your water temperature was about 105-110c. Then it would have shot up like a 13 year old boy on viagra.

So if it actually got all the way to the end of the guage it might be bad news... That's the sole reason I fitted a mechanical temp guage to the surf (same motor) so that I can see what's REALLY going on with the coolant temp.

So umm, yeah, might be bad news....
AnswerID: 240534

Follow Up By: Roktruk - Thursday, May 17, 2007 at 16:14

Thursday, May 17, 2007 at 16:14
So where does the sensor for the gauge go? Is it using a screw in VDO type or a thermal probe in a hose somewhere?
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Follow Up By: jeffwa - Thursday, May 17, 2007 at 16:23

Thursday, May 17, 2007 at 16:23
I used the hoses that went to and from the throttle body heater. Figured I don't need that in WA. :-)

So basically there are two small coolant hoses, one that comes from the block and into the throttle body. The other comes out and returns back to the block.

I just disconnected them, screwed the probe into a brass "T" peice and clamped the two hoses to that. Then I just put a dob of silicone over the inlet and outlet of the throttle body heater. Never noticed any difference whatsoever from disconnecting the throttle body heater either. Was an easy installation. Hardest bit was getting the probe through the firewall as I already had air hoses and 2 bits of 4 gauge electrical wire going through, not to mention the dozens of smaller wires that I had to put through. LOL
FollowupID: 501492

Follow Up By: jeffwa - Thursday, May 17, 2007 at 16:34

Thursday, May 17, 2007 at 16:34
Here's a pic of the throttle body for you:

FollowupID: 501494

Reply By: Roktruk - Thursday, May 17, 2007 at 13:41

Thursday, May 17, 2007 at 13:41
That's kinda what I went from "All's well under here" to "OH S%$#" real quick. i sold the 80 (91 Standard with 280K - most of them very hard) before something went wrong and I had to spend money on this type of problem.

%$^&* hi-tec diesels.....Apart from that - love the car, comfortable, heaps of go, good economy
AnswerID: 240535

Follow Up By: jeffwa - Thursday, May 17, 2007 at 14:10

Thursday, May 17, 2007 at 14:10
She's not really that hi tech, the motor's similar in age (design wise) to your old 80. Mine's a 95' and they started using the 1kz-te in the surf's in 93'.

If it had a cast head it still may have cracked from being overheated, but they are generally a little more robust as they the alloy is generally a little more brittle.

The question I'd be asking is why did it overheat? I doubt the cracking of the head would have caused the overheating, more like what ever caused the overheating resulted in cracking the head.

Blocked radiator, stuck thermostat, water pump???
FollowupID: 501465

Follow Up By: jeffwa - Thursday, May 17, 2007 at 14:11

Thursday, May 17, 2007 at 14:11
"cast iron" that should have been.. :-)
FollowupID: 501466

Follow Up By: Roktruk - Thursday, May 17, 2007 at 14:16

Thursday, May 17, 2007 at 14:16
Of course, that's my worry. Getting hot is a symptom, so where's the cause?? Off to Hume Off Road (ACT) on Saturday - sharpening the credit card now.....

The alloy gods may be smiling and it may only be the gasket.....
FollowupID: 501469

Follow Up By: jeffwa - Thursday, May 17, 2007 at 14:28

Thursday, May 17, 2007 at 14:28
The surf has a different radiator to the prado, so I'm not sure how relevent this info will be, but these are the typical causes of overheating for 1kz-te surfs.

Radiator blocked. (obvious one).
Viscous fan not working correctly (even if it sounds like it is, it may not be fully locking in and slipping)
Gearbox - ATF low or working the gearbox too hard (in the surfs the bottom tank of the rad is where the heat exhchanger/atf cooler is).

Generally with all of those it's normally only hard acceleration for long periods that causes it to overheat, but there will be no warning that it is getting hot until the guage all of a sudden shoots through the roof.

The prados have a 70 degree C thermostat so your running temp should be around 71/72 degrees c. Depending on how efficiantlly your rad is working your rad shouldn't get heat soaked until about 30 degrees c+ outside temp cruising at 110kph++, even then all that will happen is your running temp will increase up to what ever temp the viscous fan is set to cut in, then it'll drop back down again.

When there is something up the bleep ter it get's heatsoaked and runs hot (not that you would know as the temp gauge would still be on half). Then it doesn't take much (just a longish hill or some soft sand or whatever) to bring it over the edge.

For example, the surf has a 90 degree thermostat. It sits at 91 normally, highway cruising 30 degrees + it stits at about 98/100 degrees, if there are hills, overtaking or the outside temperature get's hotter the viscous fan cuts in at about 102c then it roars its nuts off until the temp drops back down to 95c and cuts out, it'll cycle like that on and off all day if it has too.

But I can still get it hot if I'm overtaking up hill or doing some really boggy sand sections because the temp goes up so fast the viscous fan doesn't get a chance to lock in in time and I have to back off until it does and then the temp drops back down again.

Don't know if any of this helps, hope it does! ;-)
FollowupID: 501471

Reply By: GeoffMc - Thursday, May 17, 2007 at 19:00

Thursday, May 17, 2007 at 19:00
Before you get all hot and bothered about a head repair/replacement, just remember that a blown head gasket will give you the identical symptoms. Have a qualified mechanic check it out. Once the head's off, it's a pretty simple diagnosis.

AnswerID: 240594

Follow Up By: Roktruk - Thursday, May 17, 2007 at 21:45

Thursday, May 17, 2007 at 21:45
Qualified mechanic did have a look - me - since 1982.....

However, don't really feel like crawling around under the bonnet anymore (unless someone is paying me!)
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Reply By: hiab - Thursday, May 17, 2007 at 20:33

Thursday, May 17, 2007 at 20:33
my moneys on a blown head gasket, have a pressure test done and see if it loses pressure, it only takes a small blowout in the gasket to lose pressure. any water in the oil or inside the rocker cover? the head will crack if driven repeatedly very hot, if a head gasket, no big dramas, they sometimes just blow. and also check that there is not an air pocket in the cooling system, which will cause the coolant to aerate and blow bubbles.
AnswerID: 240620

Follow Up By: Roktruk - Thursday, May 17, 2007 at 21:41

Thursday, May 17, 2007 at 21:41
Well, limped it home, couple of stops to check/top up the water. Radiator cap off and the heater running to dump a bit of heat - lucky it's approaching winter in Canberra (apparently). Oil is not contaminated and no indications of water getting into anything else. It didn't lose a lot of water on the trip and the temp stayed just below centre gauge where it always sits. Slight bubbling in the radiator, not geysering like I've seen a Disco with the same problem do.

Fingers crossed on a head gasket 8~/
FollowupID: 501571

Reply By: GerryP - Thursday, May 17, 2007 at 21:51

Thursday, May 17, 2007 at 21:51
Same thing happened to one of our club members on a trip a while ago. It is apparently relatively common for these vehicles to crack the head at number 3 pre-combustion chamber, according to a Toyota dealer we checked with at the time. Fortunately, he was able to convince Toyota to come part way and pay for the head while he paid labour costs even though the car was out of warranty. This further indicates to me that it is a known problem.

I hope this is not the case for you. It would be interesting to have an exhaust gas temperature (EGT) meter fitted to see what it gets up to under load. Don't know whether this applies to you, but the vehicle above does lots of fairly heavy towing which could raise the EGT to a level where such damage may occur - maybe someone reading this has a Prado with EGT guage that can shed more light on this possibilty?

Good luck
AnswerID: 240651

Reply By: hiab - Thursday, May 17, 2007 at 21:54

Thursday, May 17, 2007 at 21:54
i reckon you will be ok, just make sure you get a pressure test. if it holds pressure, then you have to look somewhere else, water pump or thermostat would be the suspects, did you buy the car new? if not 7 years on, time for a radiator service. if you got it second hand, you really dont know what has been in the e ngine. we get cars from lajamanu, yarralin, kalkaringi, that have had muddy creek water in them, and blocked the radiator. anyway, to get the rad. done cost wise, well up here in katherine we pay $90, so check it out. thats trade by the way.
AnswerID: 240652

Follow Up By: Roktruk - Friday, May 18, 2007 at 12:05

Friday, May 18, 2007 at 12:05
Bought second hand a few months back, one owner with full service history. It was used as a tourer, sequential receipts from all around Australia every 5000ks(can track where they went!), but it was never used to tow a van as there is no towbar and no indication of one ever fitted. No indications anywhere of previous problems, just one of those mechanical things that can occur.

I would be interested in any info and claims people have had against Toyota for craked heads if this is the case. Of course, the dealer warranty isn't worth the paper it's written on "DOES NOT COVER DAMAGE DUE TO LOSS OF COOLANT" well DUH, what's the main cause of engine failure???
FollowupID: 501662

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