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Overheating

GDB

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Jan 4, 2022
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australia
Hello - New to the forum.

Purchased an 80 series 1Hz diesel 6 years ago 380,000km (now has 440.000km) on the clock - lm the 2nd owner.

lm far from mechanically minded - but know some basics (oil change , fit brake pads , fuel filter etc)

The vehicle runs well , it uses approximately 500ml to 1lt of oil every 5000km.

Fuel consumption 14 Ltr for 100km (country roads)

The car is fitted with a Engine Guard temperature gauge (it has been verified at operating correctly) - it runs at around 80 degrees C.

When under load - small camper trailer - it will run at around 90c up over 100c.

l have done a bit of research over the years & have discovered it is a pretty common problem and took advice on how to deal with it including addressing the usual suspects - viscus fan , new radiator , removal of driving lights (restricting radiator) , thermostat , engine flush , bubbles in coolant etc.

lm nearing retirement age and have to make a decision if to do a rebuild (as l will be hitting the road with the camper trailer)

l have two questions

- Is it OK to run the engine at 90c to 100c degrees (my local mechanic owned a 1Hz for many years with the same problem & he said he did run it at that temperature all the time without issue. (I will note at this point which l was unaware the factory gauge on the dash board will not show the needle gauge in the red zone at high temperatures)

- After investing in a rebuild will the over heating be eliminated?

Any friendly advice most welcome.
 
In my experience an engine rebuild will not cure overheating. Engines only need rebuilding when they are worn out. Having said that there may be debris in the block shielding the cylinder walls from the cooling water. Unlikely as the debris builds up from the bottom whereas the heat build up starts at the top.
Overfueling may cause overheating. Get someone to follow you when you have the trailer on. Black smoke from the exhaust = too much fuel and can lead to overheating. Has the pump been adjusted too much?
You may have fitted a new radiator but is it adequate? If Toyota supplied one it should be OK.
Members here may say your temperature range is normal so you may have nothing to worry about.
 
I don't think a 100 deg coolant temp will do any harm TBH. If it starts heading towards 110 then I would be concerned. The point of having a pressurised cooling system is so the engine can run at 100+ without boiling over. If it's the same OEM guage as fitted to the 1HD-T/FT it covers a very wide temp range and the engine will have to get very hot to get near the red zone. On the 3 petrol motorcycles I own the temp has to go above 100 before the fans cut in. If the fuelling has been tweaked then an EGT guage will tell you what's going on with piston/exhaust manifold temp which is equally imrortant.
 
Welcome to the forum.

First as mentioned the temperature gauge is damped down, there is a mod that can be done on the 1HD-T (I did mine) which corrects the problem, but as you have another gauge I would put that aside for the moment. If you turn on the heater does the temperature drop, is the heater hot? You seem to have covered everything, but has the problem only been a recent thing i.e. since fitting the trailer? Is there any loss of coolant. Do you have the right amount of antifreeze in the system? There is an auxiliary fan that can be fitted to the front of the radiator but this would be masking the problem if one actually exists? Any recent mods sump guard for example. a winch.....and so on? Is the fan shroud fitted and any sponge that is normally fitted between the radiator and it's mounts fitted? One thing I would look for is brown sludge in the bottom expansion tank, this could indicate rust in the system and it may need a flush?

I think running at 100. is not an issue and when my 80 is fully loaded (3 ton+) when climbing mountains here in Spain I had seen 110 when comparing gauges and have had no trouble whatsoever in the 11 years I have owned her. But wanting to keep the engine cooler I tried the modified viscous fan but they tend to drive even when the the engine is cool, this makes them inclined to add to fuel consumption, so like pretty much of all of my cars (Including a 6.0 V12 Jaguar Coupe), I do not run the OE viscous fans, I always convert to all electric, and the 80 is no exception which is now all electric, but have never had problems.

Finally I would have the coolant checked for gases coming from a weak head gasket, sometimes when the engine is worked the head can 'lift' allowing gases to get through the head gasket into the cooling system, it would also indicate a crack in the head but that would be a first in my experience, so get the coolant checked for combustion gases.

I hope I have give you some ideas or perhaps put your mind at ease?

Regards

Dave
 
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I would say 100C is a little high ... is the gauge accurate? .... try this, drive the car under loaded conditions with OUT the rad cap fitted, if the water boils over you need to do a fix ... I have a 1920 car that had a high running temp if ever in heavy slow traffic in summer - the cheap and fairly easy fix was killer simple. I took a house heating pump, plumed it into the water way of my car and ran the pump for 6 hours with a strong mix of rad cleaner solution in the rad, I started the car probably every hour for a few mins - until up to running temp with the domestic house pump running. it worked a treat, their was obviously silt which needed flushing out and any other silt which was about to partially block the cars water ways was removed .... BTW all internal heaters were left fully on so they also got advantage of the wash and flush. At the end of the days flushing I removed the domestic heating pump and extended hoses and refitted the existing hoses, filled the car with clean water and PERFECT .... costs probably £8 for 2 X tins of rad cleaner and some sparks - I had an old domestic heating pump and some 40mm hose. this probably took 3+ hours of physical work and some aptitude and saved me a small fortune at the garage!
 
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I would say 100C is a little high ... is the gauge accurate? .... try this, drive the car under loaded conditions with OUT the rad cap fitted, if the water boils over you need to do a fix ...

Can you give me an alternative reason why all vehicle cooling systems are pressurised other than to prevent boiling at 100'C +?

Talking about old cars, my 70's V12 coupe had a 20 psi cap to stopping water boiling until up in the 110'C + range.........why?

Regards

Dave
 
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the presureised system is really only about allowing the water temp to go beyond boiling point - of that I am quite sure .... this can happen in high load and high heat conditions - but for most normal running occasions the water rarely goes beyond 98C in a good performing car - Diesels normally run cooler
 
I wouldn’t be too concerned about that either, you could have a coolant system flush done, change of thermostat to a lower opening temp and replace the coolant with a waterless type, this will increase the boiling point of the coolant. It could be worth having an exhaust gas temp installed, this will let you know if you are really overheating on the combustion side of things, which will give you a higher coolant temperature, and a new set of things to start looking at!
 
the presureised system is really only about allowing the water temp to go beyond boiling point - of that I am quite sure .... this can happen in high load and high heat conditions - but for most normal running occasions the water rarely goes beyond 98C in a good performing car - Diesels normally run cooler


But you have already suggested the OP run his car under load and see if it boils with NO cap on it, and now you say under normal running rarely goes beyond 98? So now you have given him the understanding that there is only 2'C difference between a normal load and a high load running temperatures?

So which is it?

Take my word for it, engines often hit 100'C + when working, this is the reason the pressure cap is there.......no other reason...period.

Regards

Dave
 
It’s been a long time since I did my theory during my apprenticeship but I’m sure it’s 1.3bar for a normal radiator cap which raises the boiling point of straight water to around 120c, the use of correct Toyota coolant brings this to 125c under the pressure of 1.3bar
 
I would say 100C is a little high ... is the gauge accurate? .... try this, drive the car under loaded conditions with OUT the rad cap fitted, if the water boils over you need to do a fix ... I

Oooh, I wouldn't recommend trying this TBH. The coolant will expand and start filling the the expansion tank before it hits 100 deg. I've done this inadvertently and within 2-3 miles from a cold start I could smell coolant and sure enough, it was spewing out over the top of the filler neck. I hastily refitted the cap which, thankfully, was still sat on top of the driver's side battery where I'd left it and the lost coolant was replaced from the expansion tank when it cooled down. No idea what the temp was but it was nowhere near "boiling point".
 
It’s been a long time since I did my theory during my apprenticeship but I’m sure it’s 1.3bar for a normal radiator cap which raises the boiling point of straight water to around 120c, the use of correct Toyota coolant brings this to 125c under the pressure of 1.3bar


Depends on which site you check it on Google. :thumbup:

I could not remember the equation but could not resist Google, they state 1.3 Bar water will boil at 124'C so you were pretty close.

With the boiling point going up 3'F for every 1 psi it would mean my old jaguar running it's 20 psi cap meant 140'C before it would boil, I run antifreeze (of course) but cannot remember brand/coolant and so forth, but back then it would run 13 second 1/4 weighing in at 4,220 Ib in legal street trim....ahh those were the days.........


Regards

Dave
 
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If you're that concerned about boil overs just flush and refill with a waterless coolant like Evans or similar with boiling points of 190+ dec C. They won't necessarily make your engine run cooler, just that they'll never actually boil over.
 
Its alway ran at that without problems so i'd let sleeping dogs keep snoring . Maybe fire some of the various snake oils products into the mix just because they don't do any harm and i'm inclined to think they can do some good sometimes .
 
Sorry only trying to be helpful and give my inquisitive experience these past 30+ years with these LC's - my basic care solutions - as stated have given me trouble free millions of miles.
I am sure as I can be the Petrol V8's never passed 98C and the diesels Maxed out at 90C with or with out the roller screen to reduce cooling in winter
 
I guess blowby might account for the lost oil and possibly a slight increase in heat given its burnt off along with your fuel .

I vaguely remember wasting a few hours investigating via google when somebody else posted a similar question sometime back and discovering it is indeed a very common and baffling issue most learn to live with .

I prob posted this snake oil vid on that post as well
 
So, my OEM Toyota rad cap has 0.9 stamped on it. Meaning it starts to release pressure at less than 1 bar and just over the thermostat temp which I think is something like 88deg C.

These are not fully sealed systems (like on my Berlingo, which has a pressurised expansion tank).

As the temperature drops the overflow bottle ‘refills’ the radiator. Hence the importance of your rad cap - it works in both directions (if that makes sense )
 
Pretty much correct, but your Berlingo is not a fully sealed system, the cap may not show a pressure relief spring but trust me it is there in the moulding and it will release air pressure as it builds, but the water level is far enough down to prevent loss under normal conditions when the air is released, only in severe overheating is the amount of pressure/water expansion so high that the water rises in the expansion tank and is lost through the cap, if you look at the cap threads you will see there are areas where the cap threads are missing, this allows air/water out. The Toyota is about expansion of the fluid and as you say drawing it back as the engine cools. On the Berlingo the amount of controlled air above the water level keeps it more or less level between cool and hot, the caps are typically rated higher as modern systems run at similar temperatures as you state however, the higher rated cap allows the engine to get much hotter before the electric fan kicks in.

Regards

Dave
 
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