Over Heating Hilux

ghumphreys

New Member
OK Guy's i need some help as well as my 80 series i all so have a 95 Hilux RN105 Petrol, and up until monday it was running fine. Got home from work approx 80km drive pulled up and could hear the sound of a boiling radiator check gauge again as i do regulary while driving gauge was fine, removed rad cap to find it needed about 3-4 litres of water. Next day on the way to work had to top up the radiator twice to get to work. Droped it off at a workshop to find problem but to my suprise the could find nothing, They TK tested it pressure tested it but could find nothing (did replace rad cap as it was allowing a little blow by) On the drive home same problem again, took it to a local workshop he also TK tested it and pressure tested it for over 3 hrs with no result, endoscoped the cylinders all looked fine. Please any suggestions would be a help
 

billolga

Well-Known Member
Yes but where is the water going

Fishigan could be onto it.

I had a Thermostat crack in an old car in such a way that it didn't open - the water went out the plastic top up tank like a fountain.

Take it out & see how you go.
 
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Fishigan

New Member
exhaust port maybe

Would have picked that up in the pressure test.

Given that it's been pressure tested and scoped, I'm assuming that there's nothing wrong with the head gasket, hoses and water pump. Its got a new rad cap so I'm thinking that the water is escaping out of the overflow at high revs. That would point towards a restriction which would point towards a sticky thermostat or a blocked radiator.

I'd be removing the thermostat and flushing the system before putting a new thermo back.
 

NIAL8R

New Member
thermostat is either stuck and only a little open not allowing the water to flow free, also check your top and bottom hoses as thone of them may be shagged ( i.e ) sucking in under high rev's then when you back off it rushes straight through to the over flow.
 

LowLux

Moderator
If they can't find anything wrong with pressure test etc over heating can be caused by something a small as having spotties in front of the radiator.
 

ERASER

Member
a cracked head will not always show up with a presure test. Depending on how bad the crack is and at what temp it needs to get to before the crack opens.
 

red hilux

Well-Known Member
Would have picked that up in the pressure test.

Given that it's been pressure tested and scoped, I'm assuming that there's nothing wrong with the head gasket, hoses and water pump. Its got a new rad cap so I'm thinking that the water is escaping out of the overflow at high revs. That would point towards a restriction which would point towards a sticky thermostat or a blocked radiator.

I'd be removing the thermostat and flushing the system before putting a new thermo back.

maybe, maybe not.

If the engine is cold when you tested for it, may get a clear result. As the engine warms up, the crack opens up causing the leak
 

Fishigan

New Member
maybe, maybe not.

If the engine is cold when you tested for it, may get a clear result. As the engine warms up, the crack opens up causing the leak

I know I assume a lot BUT, I'm assuming that the guy that did the pressure test knows what he's doing.
Pretty sure you'd notice a bit of discoloring or something with the scope as well. (Assuming the guy knows what to look for that is) :D:D
 

ghumphreys

New Member
Update on over heating Hilux

Thanks guys for your comments.

I also assume they know what they are doing and since two different people got the same results i am assuming they are correct.

After a bit more investigation i think i have located where the water is going, it is still getting pumped out via the overflow / recovery line and because it was also hot when i removed the rad cap you get that sudden rush of water and steam, so i may not have actually have lost as much as i thought however i am sure if i kept driving it would eventually run out.
I have now tested the thermostat and it tested fine but while i had it out i ran it and still got the same results. I have also replaced the water pump.
So to recap.
Replaced Rad cap
Replaced Water Pump
Checked & Removed Thermostat
Had System Pressure Tested (Tested Fine)
Had System TK Tested (Tested Fine)
Scoped the cylinders (No sign of any water etc.)

Symptoms again are after about 15min of running at 2500 - 3000 rpm or about 30k's
the temp starts to rise, at this stage it is blowing out the overflow / recovery line. Have spoken to a Radiator specialist and his opinion is more than likely a head gasket even though the other test came back ok.
 

Sabbath

Member
Thermostat. I had the same issue in my lux.

Replaced:

Thermostat
Waterpump (timing belt while i was in there)
Lower Hose
Radiator
Also removed fan and topped up the fluid in the coupling


and she still overheated. Removed the thermostat altogether and she ran like a charm. Bought another thermostat and she hasnt given me any grief since.
 

35Henry

New Member
Have spoken to a Radiator specialist and his opinion is more than likely a head gasket even though the other test came back ok.

What did he say about the radiator? That would be the first thing I would have checked. I remember back in my days at TAFE our books listed about thirty reasons for overheating but the teacher said in practice about 90% of problems will be caused by a blocked or partially restricted radiator. I spent 19 years in the industry and found that he was right.

A simple test is to remove the lower hose then fill the radiator with water from a garden hose while you block the lower outlet with your hand. Remove your hand and watch the water flow out. It should gush out rapidly in a few seconds. If it trickles out, or looks like it is being poured out steadily, then the core is restricted.

If you have any doubts then either get the radiator professionally cleaned or replace it. If it is many years old then it is not a bad idea to buy a new one. They don't work efficiently forever even if they have been properly maintained.
 

Fishigan

New Member
Start your car up, wait til it starts to overheat, then pull your spark plugs out and see if one looks a little browner than the rest or if ones a little wetter than the rest. Turn the engine over without the spark plugs in, see if anything comes out the spark plug holes.
 
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baby_troupe

New Member
Have a similar situation with my 95 series Prado Diesel only have replaced a few more bits.
Replaced Head, thermostat and gaskets
Replaced all hoses
Water pump tested and is as good as new, both cold and hot.
Replaced Radiator
Replaced Radiator Cap.

Coolant is all going into the overflow bottle.

Next to be done is some special oil for the thermo fan.
 

Fishigan

New Member
If it's coming out of the overflow bottle, Its caused by either a restriction or too much air in the system.

With a restriction, coolant flows from the engine, through to the top of the radiator but doesn't flow at the same speed after that which causes a build up of pressure and sends the coolant out the rad cap. Normally, it would be a thermostat problem or a blocked radiator. Sometimes the restriction can be in the engine itself and would require a deep flush.

With too much air in the system, it can be whats called an "air lock" which is air that's trapped in the engine. Because there's not the right amount of coolant in the system, the coolant and air get too hot and turns to steam. The steam expands and forces the rad cap to open and go out the over flow. Some engines have bleed screws to get all of the air out. Some, you just have to run for a long time with the heater on and the rad cap off till all the air escapes.
Another "too much air" problem can be if the head has a crack in it or the head gasket is blown between the cylinder and a water gallery. The air is coming in via the compression stroke of the cylinder into the water gallery and pressurizing the cooling system and forces the rad cap to open and go out the over flow. The best way to check this at home is to fill the radiator and run the engine with the cap off. If you look down the hole where the cap should be, at first, you might see some bubbles. They should go away. If they don't after about 15-20 mins, chances are you have a blown head gasket or cracked head.
You may have creamy colored oil too BUT NOT ALWAYS. This is because the leak in the head is between the oil gallery and the water gallery.
Hope this helps.
 

fc59

New Member
i have a simmilar problem with my 97 2.8 d

wont boil in trafic or on a hot day or 4wding on any thing but as soon as she hits sand bingo :mad:
i do understand that running 33 muddies is not ideal on sand as well as having a steel bull bar with a steel tray with a hard wood deck and the lead floor insulation as well as bolting all the other things to her im asking a lot and the steel snakeracing crossmember that ways a tone

when put my panel van back together ill take the hilux off the road for a month or two and do some servicing maby also some painting
 

5arah

New Member
Oh god, I'm reading this & ticking all the boxes as I'm currently stuck in Mt Isa with an overheating Hilux & the mechanics can't diagnose what's wrong with it.

It's a 1996 dual cab Hilux disel 2.8L manual. She's done alot of Outback dirt but has never overheated. I notice 2 pinhole leaks in the top of the radiator last week & as I was about to do a 3500km drive, I thought it wise to get it checked.

The mechanic fitted a new radiator & since then everything has gone pear shaped. It overheats like hell after 15mins of driving.

She's now a different mechanic & in the last week, she's had fitted:

new radiator & new cap (Made in Indonesia stamped on it & priced at $600 - whaa?)
new hoses & clamps
new thermostat
new fan clutch
new coolant
2 x pressure tests were good
TK test was good (no cracked head)

... and it's still o/heating and the mech still can't diagnose the problem.

He thinks the pressure is coming from inside the engine & pushing outward (which perhaps caused the original pinhole leaks?).

Me? I'm just a girl who is haemmoraging money in parts, labour (already it's at $1400 with no end or solution in sight) and accommodation.

I read this thread and it sounded so very familiar & I wondered whether anyone in Internetland might have any suggestions because the best that the mechanic can say is:

"She's an old engine."

She may be old but historically, she's never had a problem. All this started when the new radiator went in.

I'd be grateful for any help whatsoever.

Thank you so much.

Sarah
 
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