1hz diesel overheating, any suggestions please

[Robbos_Toyotas]

Hi all,
my uncle has a 1998 75 series cruiser ute with the 1HZ non turbo diesel
since he has had it, it has always got hot under load - climbing a hill, with or without a trailer and it basically boils instantly under these conditions.

he has already done:
new massive 5 core radiator
new thermostat
renbuilt injector pump
checked water pump
viscous fan replaced with a huge commodore electric fan, thermally controlled (this hasnt caused the problem as it was boiling before) even with new fluid in the clutch fan.

does anyone know what the problem could be, i hear 1hz's are pretty common to get hot...

thanks
Blake

[thechuckster]

cracked head?

the 3L 4cyl diesels crack between valve seats and either the combustion chamber or from head face into the water jacket - this might have done similar

[Robbos_Toyotas]

i have thought about that, but it doesnt use a heap of water n there is no water in oil or vice versa?

[TurboRA28]

I had same problem with my 75 series troopcarrier 1hz.. I could never solve the problem. It sucked as it made it pretty useless as a tow vehicle as every long hill it'd overheat on. Wasted money on new radiators and thermostats etc.

Ended up selling, buying a 80 series petrol and never looked back.. Sorry not a solution I know.

[Robbos_Toyotas]

did u do the head or compressoin test it?

[hosking1991]

These heads often leak beneath the pre-combustion chambers which means that the water will not contaminate the oil but water will still be lost

[thechuckster]

Blake: time for your uncle to get a different engine or pull the lid off and get reco head.

fwiw: There's a co. in BNE that specialises in reco heads for diesel motors (Mick's dad got a 3L head and parts and gaskets for just under $1k at trade prices - he only needed some shims to finish the job). I'll try to find the name and PM you.

There's so much torque holding the head down that the head gasket doesn't usually fail between the oil and water galleries. Cracks in the head are usually between combustion/valve seats and water gallery.

the higher combustion/compression pressures ensure that water doesn't get sucked into the chamber (unless the crack us massive) but when running you get increase in coolant pressure and massive boiling.

If it's been boiling under load from purchase, the head was probably already fubar. It should hold temp unless you are trying to tow a 30foot steel hull boat.

[Robbos_Toyotas]

thanks guys, really appreciate ur help hey

[cambelt]

I know you said the electric fan hasnt caused any dramas but there is no way it will pull the kind of air the factory toyota fan pulls. I spose if you lived in a colder climate an electric fan could be a saving .
A 1HZ fan should nearly blow your hair out when its in .
Dave

[2jzhilux]

I think dave could be onto something there
ive seen a lot of times the viscous fans are taken off and then the car will overheat because there is no electric fan that could keep up with the fan on the motor.
but since you said it was doing it before id say it would be cracked head inside the pre combustion chamber, have seen landcrusiers and hilux's do it in the same area but you cant see it if your inspecting it with the head off .
Have you tried pressurising the cylinder with a diesel compression tester fitting and an air compressor and looking for bubbles it the coolant or do a tk test.

[Robbos_Toyotas]

yeah im aware the thermo would not pull as much air as the original one, and if he decides he wants to keep the car ill probly put a clutchie back on it...its just the $ factor of a new head...

[blakeg]

yeh we had the clutch fan go in our 80, it was fine untill it was really working, then it would creep up,

the clutch fans on these are nuts hey, suck through soooo much air.

[cambelt]

Funny as i just completed a 2500klm trip to sydney in my 7M powered Cruiser and when in Syney City with the A/C on i remember one time the clutch fan dropped out , thats strange i thought but didnt think much of it as the temp was still fine .
Now a few days later and 600 odd klm leaving Cooma this morning i saw the temp sky rocket after about 10 min of driving , same thing the clutch fan dropped out again .
The reason why ?? 3 year old rad cap wasnt holding propper pressure and letting too much water out when it was working hard hence in the end leaving the engine short of about 3 lt of water .
Air pockets in the rad mean the clutch fan would be reading colder than normal air and dropping out .
Dave

[Robbos_Toyotas]

ahh the old $5 part does the damage hey dave....always the way eh

[matty12]

first post so here i go.

Do you find it has full pressure within the system when its stone cold (im assuming the cap is in good working order)?