2.5L Diesel Overheats While In Neutral With A/C Running...

[Ahnsahn]

A 'reconditioned' 2.5L diesel in a '98 Toyota Mighty x pickup truck which otherwise runs flawlessly, will overheat only while idling in neutral and with A/C running.

The A/C always puts out ice cold air but after idling in neutral for several minutes, the cold air temp gradually decreases and the temp gauge starts creeping up toward 'Hot'.

The only other relevant notes are:

- The car's 4 speed temperature blower switch is inoperative at its 2nd speed setting. (Could this malfunctioning blower switch be the culprit?)

- The engine also overheats (with A/C running) when having to perform a series of downshifts in order to make it up very steep mountain grades.

- Though there is no tell-tale exhaust 'smoke' or visible oil leakage, I do have to add a liter of (semi-synthetic 10w-30) oil after every 400 km-500 km road trip.

- I have had the coolant(50-50) and thermostat changed twice and new hoses installed.

The engine idles just fine in neutral w/o problem when the A/C is off.

Can anyone help find a solution to this overheating problem?

Edited November 17, 2011 by Ahnsahn

[Semper]

I think you have some problem with the radiator fan.

[ludditeman]

I second that, radiator fan not working.

[wandrinstar]

Has it got the old Viscous Type Fan , not Electric. If so the fans just Feathering , not Blasting at hi revs. Lucky you if its that simple. The A/C cuts from working too hard automatically , like if you leave the window open.

[Ahnsahn]

Hey guys, thanks! I'll look for a viscous fan replacement tomorrow.

[Kwasaki]

I think you have some problem with the radiator fan.

That was my first thought. !! AC sensor setting ?? Does the fan come on and as said what type is it... ??

Q. ( Blower switch is inoperative at its 2nd speed setting. (Could this malfunctioning blower switch be the culprit?)... No !!

( A 'reconditioned' 2.5L diesel in a '98 Toyota truck )... Was it OK before this work was done.??

( The engine also overheats (with A/C running) when having to perform a series of downshifts in order to make it up very steep mountain grades.)... Again did it do this before. ??

Does it actually gointo the red... ??

( I have had the coolant(50-50) and thermostat changed twice and new hoses installed )... Was the system flushed and radiator blockages checked they can get clogged or blocked. ??

[Semper]

Hey guys, thanks! I'll look for a viscous fan replacement tomorrow.

Can you post how much it is? I have the same car as you, but my problem is the opposite. The clutch in the fan is stuck so it's going at full speed all the time, quite noisy above 90 km/h. No overheating though.

[wandrinstar]

If its like the old Nissan Big M import , there is a Pressure Grease Gun Point no one ever noticed, take a peak first.

[Lickey]

Im with Ksawasaki on this one, usually, well, UK anyway, if you had a new engine, or recon, there would be no guarantee unless you re-newed the radiator, with the extra heat generated by a new engine, it needs all the cooling it can get, some of the older viscous fans had a lock-up plate on them, i think its on the pulley side of the fan, something like, release 3 bolts, move the fan round and the plate will click into place, tighten bolts and the fan will be on engine speed all the time, <BR><BR>Just another point, if the people who changed your engine laid the fan down flat, this will also mess up the viscous coupling quite a lot..

[Ahnsahn]

( A 'reconditioned' 2.5L diesel in a '98 Toyota truck )... Was it OK before this work was done.??

( The engine also overheats (with A/C running) when having to perform a series of downshifts in order to make it up very steep mountain grades.)... Again did it do this before. ??

This current 'reconditioned' engine is not the original engine.

Does it actually go into the red... ??

Yes.

( I have had the coolant(50-50) and thermostat changed twice and new hoses installed )... Was the system flushed and radiator blockages checked they can get clogged or blocked. ??

The previous owner had this radiator installed at the time of the 'reconditioned' engine install.

Has it got the old Viscous type fan, not Electric. If so, the fans just Feathering , not Blasting at hi revs. Lucky you if its that simple. The A/C cuts from working too hard automatically , like if you leave the window open.

I believe it's a viscous fan - I'll make sure in the morning - but I just checked, and I do know it's not feathering! With the engine running, I tried to stop the fan blades from rotating by using a stiff notebook but the fan was as strong as ever and couldn't be stopped!

Thanks guys....and I was hoping I had a clear case of feathering! Are there any other ways to diagnose this overheating problem?

[MTH]

( I have had the coolant(50-50) and thermostat changed twice and new hoses installed )... Was the system flushed and radiator blockages checked they can get clogged or blocked. ??

The previous owner had this radiator installed at the time of the 'reconditioned' engine install.

Two interesting points here.

If the radiator has been replaced, it could possibly have been replaced with one of a smaller capacity, and therefore being under-dimensioned for your engine.

Also you mention having changed the thermostat twice. You should be able to buy a thermostat that opens up fully at a lower temperature. I don't remember the range on top of my head, but it's usually something like 68 to 72 degrees Celsius. So why not look into getting a thermostat that opens up at the bottom of the range, somewhere around 68 degrees. You might currently have one that opens at a higher temperature.

[Crossy]

I would have gone with the fan coupling too, seems not to be the problem I assume it's shifting plenty of hot air when running.

Have you tried running it without the thermostat?

Since it cooks when idling and when working hard at low road speed could the water pump be faulty?

It seems that this combination of engine and radiator has always had this issue, correct?

[Ahnsahn]

I wasn't able to get to work on the car today...... I'm hoping to be able to resolve this problem lay-oh, lay-oh and post the solution.

[soundman]

Also, for a "reconditioned" engine, it should not be using a litre of engine oil every 500 km's, a litre every 5000km's would be acceptable. If there is no idle or power (white) smoke, or noticeable blow by pulse when the oil filler cap is off, check for leaks under the car, leave it idling for 10 minutes and see if there are any spots on the ground.

[Ahnsahn]

Also, for a "reconditioned" engine, it should not be using a litre of engine oil every 500 km's, a litre every 5000km's would be acceptable. If there is no idle or power (white) smoke, or noticeable blow by pulse when the oil filler cap is off, check for leaks under the car, leave it idling for 10 minutes and see if there are any spots on the ground.

I agree and was concerned about the oil replacement frequency. I had to replace a leaky high pressure(?) oil hose. I have not noticed any leaks or blow by with the oil filler cap off but have noticed only a couple instances of 'puffs of black smoke' when accelerating while changing gears - 'N' to 'R' for example.

I would have gone with the fan coupling too, seems not to be the problem I assume it's shifting plenty of hot air when running.

Have you tried running it without the thermostat?

While contemplating my next move(s), I came across this quote in an older Toyota service Rx manual:

"Removal of the thermostat would have an adverse affect, causing a lowering of cooling efficiency. Do not remove the thermostat even if the engine tends to overheat."

Since it cooks when idling and when working hard at low road speed could the water pump be faulty?

It seems that this combination of engine and radiator has always had this issue, correct?

I hope to identify the problem - water pump, thermostat, radiator/fan.....since the overheating only occurs after approx > 5 min with A/C on at idle and while ('working under load') downshifting trying to generate adequate torque to climb really steep roads.

This 'reconditioned' engine replaced the original engine, so it's not the same machine and therein could lie some of the answers. For example, (I was told) this replacement engine uses a different oil pressure connector than the original engine, thus I have no oil pressure readings.

Edited November 19, 2011 by Ahnsahn

[TommyDee]

You have had some good replies here already but lets take a look together .

Essentially .. Engine overheats under high load and revs in low gear or at standstill . AND since the a/c seems to function ok we will take that out of the equayion all together (for now)

An Engine will only overheat for the following reasons

1..Burst head gasket

2..Poor water circulation

3...lack of water to circulate

We should be able to eliminate No1 as you say the engine is good.

2&3 are related problems.

My prefernece would be the addition of an electric fan at the front of the radiator as viscous fans are notorious at slow speeds in high temps. especially with a/c on which will cause more heat around the rad.. but first..

Lets assume there are no water leaks and the rad and overflow tank are both full of clear water which has not gone brown or gungy.

SO.. the problem is circulation, which means either the thermostat, the water pump the radiator or the cooling fans are NFG.

start with the easiest possibility first. remove the thermostat, cut off the middle bit (thats the bit that opens and closes) just leaving the outer rim. this will cause you no damage here i assure you. TEST THE VEHICLE.

If no improvement have the radiator back flushed or do it yourself. its easy. simply remove it, put a hose in the arse end and flush it thru. TEST THE VEHICLE.

The water pump should have been replaced with a new one when the engine was fitted, along with a new timing belt if it has one. but by now i would start to question the pump. HOWEVER if it is not wet around its seals or at its drip hole this may not be the case. sadly until it is removed you wont know, and by then its easy to change and not expensive

I also use a tester which I have here that comes from blue point. you put blue liquid into a funnel type of unit and sit it on the water expansion tank ( overflow tank) if the water turns green the Head gasket is shot! i dont know if you can find a tech here with that type of tester, but it would be worthwhile

Good luck

[wandrinstar]

About that year they suffered from Head Distortion from overheatin when new..I remember some say the rad was too small,and they fitted a higher capacity in later ones.. Not that its helps you much. !!.

[Kwasaki]

With the engine running, I tried to stop the fan blades from rotating by using a stiff notebook but the fan was as strong as ever and couldn't be stopped !!

So the fan doesn't stop and spins fine OK.

If the radiator has been replaced, it could possibly have been replaced with one of a smaller capacity, and therefore being under-dimensioned for your engine.

Make a lot of sense check the capacity of the rad, and make sure coolant is running through it OK.

Have you tried running it without the thermostat?

YOU SAID :- While contemplating my next move(s), I came across this quote in an older Toyota service Rx manual:

"Removal of the thermostat would have an adverse affect, causing a lowering of cooling efficiency. Do not remove the thermostat even if the engine tends to overheat."

It won't hurt for a TEST I would take out the Thermo anyway just to see what happens it will eliminate Thermo problem, check to see if it is the right one and then you can always put it back.

This 'reconditioned' engine replaced the original engine, so it's not the same machine and therein could lie some of the answers. For example, (I was told) this replacement engine uses a different oil pressure connector than the original engine, thus I have no oil pressure readings.

So far !! .

So replacement engine is not a reconditioned of the original one OK.

No oil pressure reading. ??

Thoughts then !! When they do recon-engines they use a lot of the old stuff already on the engine.

Oil pump ?? Water pump ??

Still need to do the Thermo thing and make sure the rad is flowing OK etc.

Edited November 19, 2011 by Kwasaki

[philipm]

Three points to check:

1-Thermostat -maybe stuck....

2-Fan is not active when in Neutral

3-Coolent-leak

[wandrinstar]

Seems we don't have the full info on the Re Con. Must have gone round the world ten times considering its young age.. 1998 . There are 30 year old ones still on original.lump

[Ahnsahn]

About that year they suffered from Head Distortion from overheating when new..I remember some say the rad was too small,and they fitted a higher capacity in later ones.. Not that its helps you much. !!.

Contrar my dear Watson! You may have actually pinpointed the problem - I hope to know for certain after a process of elimination! :jap:

Three points to check:

1-Thermostat -maybe stuck....

2-Fan is not active when in Neutral

3-Coolant-leak

For my understanding, in #2, when you state that the fan is 'not active', do you mean that the fan is not actively drawing air through the radiator vents but it is still actively rotating? If so, how does an engine keep from overheating (with A/C and on an especially hot and humid day) while idling in Neutral for an extended period of time?

You have had some good replies here already but lets take a look together .

Essentially .. Engine overheats under high load and revs in low gear or at standstill . AND since the a/c seems to function OK, we will take that out of the equation all together...(for now).

An Engine will only overheat for the following reasons

1..Burst head gasket

2..Poor water circulation

3...lack of water to circulate

We should be able to eliminate No1 as you say the engine is good.

2&3 are related problems.

My preference would be the addition of an electric fan at the front of the radiator as viscous fans are notorious at slow speeds in high temps. especially with a/c on which will cause more heat around the rad.. but first..

Lets assume there are no water leaks and the rad and overflow tank are both full of clear water which has not gone brown or gungy.

SO.. the problem is circulation, which means either the thermostat, the water pump the radiator or the cooling fans are NFG.

start with the easiest possibility first. remove the thermostat, cut off the middle bit (that's the bit that opens and closes) just leaving the outer rim. this will cause you no damage here i assure you. TEST THE VEHICLE.

If no improvement have the radiator back flushed or do it yourself. its easy. simply remove it, put a hose in the arse end and flush it thru. TEST THE VEHICLE.

The water pump should have been replaced with a new one when the engine was fitted, along with a new timing belt if it has one. but by now i would start to question the pump. HOWEVER, if it is not wet around its seals or at its drip hole this may not be the case. Sadly, until it is removed you wont know, and by then its easy to change and not expensive.

I also use a tester which I have here that comes from blue point. you put blue liquid into a funnel type of unit and sit it on the water expansion tank ( overflow tank) if the water turns green the Head gasket is shot! i don't know if you can find a tech here with that type of tester, but it would be worthwhile

Good luck

Thanks, I will try to follow this guide!

Two interesting points here.

If the radiator has been replaced, it could possibly have been replaced with one of a smaller capacity, and therefore being under-dimensioned for your engine.

Also you mention having changed the thermostat twice. You should be able to buy a thermostat that opens up fully at a lower temperature. I don't remember the range on top of my head, but it's usually something like 68 to 72 degrees Celsius. So why not look into getting a thermostat that opens up at the bottom of the range, somewhere around 68 degrees. You might currently have one that opens at a higher temperature.

1 -- I removed the thermostat (not sure how to easily 'cut' the heavy gauge middle bit [that's the bit that opens and closes) just leaving the outer rim] and then tested the car by letting it idle w/ aircon on High for 25 min. The temp gauge remained steady - at about 1/3 the range from 'Cold'. The thermostat was a 82 degree model!

2 -- Took the car on the road and per the mfg quote above, I did notice a degradation in the 'performance' of the aircon in that the air wasn't as ice cold as with the thermostat installed. But worse, while idling in Neutral, the car overheated again at what seemed to be the same time interval as with the thermostat installed!

Does this test plus the fan test that I performed above rule out the fan and thermostat as culprits?

My Next steps: I will go to the dealership and:

1 - Determine if there is a larger model radiator for this engine.

2 - Buy another thermostat.

3 - Ask about an electric fan and price a water pump.

4 - Return home, flush the radiator and install the new thermostat then TEST THE VEHICLE.

Stay tuned!

Edited November 21, 2011 by Ahnsahn

[overherebc]

Seems we don't have the full info on the Re Con. Must have gone round the world ten times considering its young age.. 1998 . There are 30 year old ones still on original.lump

Easier to answer on a short post, not directed at you :jap:

Did the rad have a cowling fitted that may not have been replaced, if so at tickover you get a recirculating effect rather than air being pulled through the rad. Maybe won't overheat to a dangerous level but it can cause the engine to get much hotter on tick-over.

[wandrinstar]

How long does the Engine Cold light stay on ..?. Early Morn they should show cold even here. Running without a Stat is incredulous. The poor chaps getting the run-around i feel sorry for him . Good point about the cowling , often left off. Some serious Arse Kicking is needed at his Garage.

[Ahnsahn]

Seems we don't have the full info on the Re Con. Must have gone round the world ten times considering its young age.. 1998 . There are 30 year old ones still on original.lump

Easier to answer on a short post, not directed at you :jap:

Did the rad have a cowling fitted that may not have been replaced, if so at tickover you get a recirculating effect rather than air being pulled through the rad. Maybe won't overheat to a dangerous level but it can cause the engine to get much hotter on tick-over.

The cowling (the 'protrusion'/cover above the fan blades) is in place.

Lost in translation: What is 'tickover'?

How long does the Engine Cold light stay on ..?. Early Morn they should show cold even here. Running without a Stat is incredulous. The poor chaps getting the run-around i feel sorry for him . Good point about the cowling , often left off. Some serious Arse Kicking is needed at his Garage.

.....the Engine gauge (no Cold 'light') 'needle/pointer 'stays at rest at the 'Cold' end of the gauge for the normal several/few minutes until the engine 'warms up' (the thermostat opens).

[Kwasaki]

Does this test plus the fan test that I performed above rule out the fan and thermostat as culprits?

1 - Determine if there is a larger model radiator for this engine.

2 - Buy another thermostat.

3 - Ask about an electric fan and price a water pump.

4 - Return home, flush the radiator and install the new thermostat then TEST THE VEHICLE.

Stay tuned!

Test proved Fan OK and Thermostat OK.

Have you checked to see if the coolant is flowing through the radiator OK and not restricted. ??

Another Thermostat OK but check it is the right one for THAT engine.

If the coolant is flowing through the radiator OK then you coolant pump is OK.

I am beginning to suspect an oil pump fault. !

" tick-over " is the same term as idling.

Edited November 21, 2011 by Kwasaki

[wandrinstar]

I think the Heads distorted a bit , oil dissipation to fast. At the moment im IDLING , not ticking over., outside 7/11. Lost me on the Oil Pump , unless its one of those orrid dual water come oil pumps , i thought Toyo dumped that idea years back.

[Kwasaki]

I think the Heads distorted a bit , oil dissipation to fast. At the moment im IDLING , not ticking over., outside 7/11. Lost me on the Oil Pump , unless its one of those orrid dual water come oil pumps , i thought Toyo dumped that idea years back.

From my days spent under the hood, bonnet or what ever you want to call it, Yank Eng confuses people sometimes :-

An oil pump in an internal combustion engine whether petrol or diesel circulates engine oil under pressure to the rotating bearings, pistons and camshaft or camshalfs.

It lubricates bearings and higher-capacity bearings to also assist in the cooling of the said engine.

The oilpump could be (quote) oil dissipation to fast (unquote) or not enough.

A distorted head would show up in either coolant or oil.

Edited November 21, 2011 by Kwasaki

[wandrinstar]

Cooling by oil is marginal unless by Dry Sump and Cooler. Oilers run hi temp anyway.

[Neilly]

About that year they suffered from Head Distortion from overheating when new..I remember some say the rad was too small,and they fitted a higher capacity in later ones.. Not that its helps you much. !!.

Contrar my dear Watson! You may have actually pinpointed the problem - I hope to know for certain after a process of elimination! :jap:

Some of the guys in UK fit ali rads to their 2.4's to increase the cooling capability

Quite a few out there to choose from Ali Rads For Toyota's

[transam]

Could be a few things, viscous fan coupling came to mind as not responding, but l feel the rad replacement could have less veins than it should have to flow and cool the water. .