overheating 2l-t Land cruiser II

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Guest

Guest
Hi,
My friend as a LandCruiser II 2L-T (square lights 70 series), and is having
some overheating issues.
When off-road the vehicle never overheats.
Once out on the motorway doing around 50-60 mph the car temperature(using
the temp gauge) will start to gradually rise forcing the driver to slow
down(below 50ish) and all becomes well again?
So I have a few questions, which I am sure some of you must have seen this
in a 2L-T if it's the head?
Do you think it's the aged cracked head problem, that I read so much about,
is it worth replacing?
Could it be vapour lock, the radiator has no cap its separate from the
radiator, if so what would be the best way to remove the lock?
Could be something simple like the wrong cap or thermostat not working, any
quick tests much apreaciated?
Thanks
Martin.
 
G

Guest

Guest
Martin,
In this weather try taking the thermostat out for a week or so,
see if there is an improvement.
This is also the time of year when a flush and refill is not
wasted, if not done for some time.
Regards,
Clive Marks
Home: +44 1293 514600
Mobile: +44 7821 491897
Crawley, West Sussex, UK.
 
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If there is no overheating at low speed, traffic etc, I would think the fan
coupling and the rad are OK, how about the water pump, is the belt tight,
might even be worth pulling the pump out and having a look although I
suppose it's not the easiest thing on the list to check.
Malcolm Bagley
Stafford UK
FJ45 '75 & FJ45 '76
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I have been told (and I am by no means sure this is valid) that the removal
of the stat reduces a restriction on the flow of coolant and although this
sounds like a good thing, more coolant flowing around = better cooling,
because the pump and the restriction actually serve to increase the pressure
of the coolant in the block (relative to atmospheric pressure) removal of
the stat reduces the pressure of the coolant in the block. This reduces the
boiling temp and can cause localised boiling at hot spots in the block/head.
Steam is a poor conductor of heat so the hot spots get hotter. (also
cavitations when the "bubble" bursts can cause erosion of the cylinder liner
from outside but that really only occurs on engines that run constantly for
years)
Anyone able to verify or debunk any of this? I am interested because I want
to do some mods on my cooling system and am looking at an electric pump
solution, also my understanding of the electric coolant pump in the petrol
BMW X5 is it uses variable speed to alter cooling rather than a wax stat?
Malcolm Bagley
Stafford UK
FJ45 '75 & FJ45 '76
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G

Guest

Guest
Thanks Craig - seems I live in the dim dark ages.
Interesting actually, the bigger CAT engines have a similar arrangement to
what you have described and one of my plans was to use a CAT stat in a home
made housing, I sometimes wonder why I am reinventing the wheel and don't
just but a more modern (diesel) engine but I like the meddling.
Malcolm Bagley
Stafford UK
FJ45 '75 & FJ45 '76
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G

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Guest
NO NO NO!!!!!!!!!!
Never ever do that, as the thermostat has a foot valve to close off
water to the engine block and send it out to the radiator to be cooled,
if you remove the thermostat the engine will only circulate water round
the block predominantly virtually not using the radiator and causing it
to really overheat badly. In the dim dark ages when Toyota's did not
have foot valves this was a useful option.
Cheers,
Craig.
Clive Marks wrote:
 
G

Guest

Guest
Hi Martin,
It will require further investigation but, like looking for bubbles in
the cooling system while you aggressively blip the throttle with a hot
engine and the rad cap off, it sounds like a cracked head. These engines
have a unnecessary reputation for eating cylinder heads. It usually
starts with scruffy injectors which cause a wide spray pattern that
overheats the pre-combustion area of the cylinder head (this will NOT
show up on the water temp gauge) until it cracks due to thermal fatigue.
The crack will generally grow between the valve seats initially then out
to the exhaust valve seat from the pre-comb chamber. The crack will also
penetrate into the water jacket. at light load running round town or off
road the engine will often not be hot enough to open the crack wide
enough to let combustion gases in and hence push water out of the
cooling system but at higher speeds and loads it will.
You did not mention whether it is a 2LT, 2LTE, 2LIIT, or a 2LIITE if it
is a efi engine then injection timing is usually OK. If a non efi engine
then lower EGT's can often be achieved by running a walbro pusher pump
in combination with altered static timing and changing the hydraulic
internal advance curve of the injection pump.
In NZ we can buy really well made Chinese copy cylinder heads that are
beautifully made for about 2/3 the price of a genuine head.
Also throw away the factory triple pass muffler and fit a straight
through one. I like a pyro gauge as well and working the truck hard keep
and eye on it as if the cooling system is in good condition the water
temp will never show a overheating cylinder head.
Cheers,
Craig.
Martin Naylor wrote:
 
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Hi All,
Thanks for all the replies, we will test the thromostat, look for bubbles
and so on...
I will let you know the outcome if we ever get to the bottom of it.
Martin.
 
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