The Toyota Landcruiser Owners Club

[Andyk80]

Hi all,

I've picked up a Colorado 96 a couple of weeks back, which has "issues" shall we say with the cooling system.  Basically I'm uncovering bodge jobs and working to fix them.  The arches and chassis all look excellent for a 26 year old motor and for the most part make dinging noises with a screwdriver tap rather than crunches, so it's worth the effort in my book.

This evening I've pulled the rad to start the process of swapping out the water pump (and am waiting for a Tridon thermo and fan clutch as well), and I've found something interesting.

The bottom of the rad has a single hosetail connection that's unconnected on the side closest to the lower core hose, and what looks like a blanked equivalent on the opposite side.  Having pulled the rad now, I can also see two metal hoses coming from behind the engine that've been joined with a hose loop.

From reading I've done here and elsewhere, I think this is where the ATF coolant is supposed to connect to the rad as well.  I'm not hugely surprised by this as the PO had looped in place of the connections to the rear heater behind the engine, which I'm going to re-instate soon.

I've done loads of reading, and although I'm already preparing to increase the size of the fan, fill the clutch with 10k/cst oil and fit the higher flow thermo, I've not found a definitive guidance on the ATF cooling issue other than the two through the same rad can exacerbate the overheating problems.

My rad isn't leaking, but I've got boiling water and descaler in currently on the kitchen side, and the middle is stone cold.  I can go ahead and unblock it with a bit of time, or I've seen the 3 core uprated rad's on e bay.

My question is what's the best approach overall?  Although I have aircon on the car, I'm not averse to ripping it out to make way for a dedicated ATF rad, and fitting the uprated one for engine coolant.  Does that seem like a good way to go, or should the combined standard rad be sufficient with the mods I've described above?

I'll never be towing anything with my car, and apart from a suspension lift and bigger wheels at some point, I probably won't do much more than that to it.  A higher flowing downpipe/exhaust will eventually be on the cards too once I've built a working cooling system.

[Google]

[Andyk80]

Managed to find some more posts, still mixed opinions.  I've ordered a new standard combined rad and will hook it back up as intended originally until I've had chance to research further.

[diggerdave]

Some slightly worrying indications on your new truck. Hopefully it's just a series of unrelated bodges, rather than reflecting some catastrophic overheat!

Mine's manual, so I can't directly speak for the ATF cooling, but my understanding is that it's a problem with age and deterioration of the rad internals. So not a specific design fault as such (or Colorado-specific, I've seen it also reported by owners of other makes). As long as the rad is in good condition, no problem. I know some have fitted a separate ATF cooler instead but I think that's a precaution against future deterioration of the rad (or to get greater cooling for towing).

The reason for looping the rear heater hoses is usually due to leaks from the lines that run to the rear heater. They run under the vehicle and deteriorate. Reinstating will therefore probably involve replacing the pipes (3-door here, so I'm just going by what I've read elsewhere).

You will have read the horror stories of cracked 1KZ-TE heads due to overheating. My impression is that it isn't a common problem and it's possible that those that were going to crack have done so by now!

Nonetheless, keeping the cooling system in good order is a good idea. I fitted a lower temp thermostat (can't remember the details but plenty of info out there). The jury is out as to whether it's a good idea but it hasn't created any problem that I know of in around 50,000m. I also refilled the viscous fan with the oil you mention. I don't know about a bigger fan, unless you're going to go down the electric fan route. Most people, me included, use genuine Toyota red coolant. I'm no expert on coolant so at least that way I know that I'm getting the right stuff and the right quality for such a crucial job.

Look out for crud sandwiched between the coolant rad and the aircon rad. For a vehicle that may (or may not, depending on who you listen to) have only-just-good-enough cooling capacity it's a stupid location for Toyota to have placed the aircon rad, but quite common for all makes I think.
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1997 KZJ90 3.0d, 2" suspension lift, 235/85/16 Cooper STT Pros. 217k hard miles

[Andyk80]

Thanks Dave, I have indeed read about the cooling issues.  

This is really a project motor and apart from a few small spots of rust that I'll need to sort on the rear arches, the rust everywhere else I've found so far appears to be surface rust.  A summer getting filthy with the grinders and so on, should leave me with a decent truck, even if I end up having to change the head to get there.  Hopefully, it'll just be a case of changing the cooling system though, as that'd be a lot less time consuming!

I found a post (might be another forum) where someone mentioned using the 1HZ fan on the 1KZ-TE fan clutch as it puts out a lot more flow, so I've grabbed one of those.  I've also seen another reference to a direct drive fan, i.e doing away with the viscous fluid altogether.  Does make me think, if a lighter weight boss could be made to mount the fan to the water pump pulley, I wonder whether that'd sap much more energy from the engine than the viscous coupling with 10k oil does.

One for another day perhaps.  As it stands, Tridon thermo, 1HZ fan, new clutch, silicone rad hoses with a new temp sensor, new water pump, and new standard rad are the first round of work and I'm hoping that should be enough.

As for the rear heater, I've had the unit out and have de-scaled the core to unblock it (was blocked previously).  The metal hoses are indeed rusted a bit, so I'm going to replace those with insulated rubber (metal hoses underbody I'm guessing would lose heat anyway).

I'm in two minds about the aircon rad.  Bin it and get more airflow, but risk stones and whatnot hitting the main rad, or keep it as a shield of sorts.

[diggerdave]

I ditched my aircon rad and most of the system almost as soon as I bought the vehicle (long story and it didn't work anyway) and I haven't suffered any damage to the rad, despite plenty of pretty rough green laning and using it for my daily commute. So, based on my experience, I don't get the impression that the aircon rad performs much of a protective role. On the other hand my wife is still complaining about the lack of aircon and me not fixing it rather than ripping it out, so there might be that to consider too. I must admit I regret the lack of aircon... on thehandful of days a year when it gets hot.

Myself, I think I'd be wary of too much jiggery-pokery with fans, so I'd personally steer well clear of anything that involves major change. My feeling is that the cooling system works perfectly well as long as its kept in good condition - perhaps with a lower temp stat fitted. I know that some have successfully fitted electric fans, although I'm not familiar with the specific mods you mention. Sometimes people mention the supposed value of fitting an electric fan so it can be switched off on the dash when crossing deep water. I can't say I've ever noticed any problems with the standard system when doing deep river crossings, though it might be a different story if you were static in deep water I guess.
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1997 KZJ90 3.0d, 2" suspension lift, 235/85/16 Cooper STT Pros. 217k hard miles

[Andyk80]

Ok, that's encouraging to hear.  I'll probably get to the point of a working engine and see what the additional sensor has to say before making a decision on the aircon.

The direct drive comment was an interesting one, as the fan would always be spinning fully, so as soon as coolant hits the rad it's being cooled, stabilizing the up-down temp pattern I've read about.  Trade off is sapped engine power, but again, I don't think I'll look at that until I know how it runs (when it runs).

I did wonder about electric fans as I did that mod on my Trooper a good few years back and it was good for 1-2mpg increase, but those engines didn't have the head cracking issue.  Most of what I've seen re electric fans on these engines seems to be leaning towards "don't do it".

Thanks very much for the advice.  When I get to the point of a stable usable engine, I'll report back on how it's running with the mods I've mentioned.

[Andyk80]

All mods done.  Haven't hooked up a new temp gauge yet so I don't know exact temps, but I've been idling the truck for ages and have the rear heater working well.  Main heater is blowing luke warm or building up heat with fans off, so I think it's a blockage to be flushed.

It's only idled so far, but with engine fully up to temp (I've also ripped out the A/C) the top couple of inches of the rad gets nice and hot, while the entire rest and the lower hose are stone cold.  New rad and v8 fan seem to be doing nicely.  Also no sign at all of bubbling/frothing at the rad cap, so it's looking hopeful.

For anyone else thinking of it, the 1HZ fan blades are a straight bolt on replacement for the standard ones.  Bolts straight onto the 1KZ-TE fan clutch and away you go.