Coolant Temps. What should they be?

[brucemillar]

Folks

There are various threads around just now that ask about coolant temps and what should be expected. I have a very personal interest in this subject, so thought it may help if we had a thread where people could ask general questions without being tied to a specific model and risking a thread hi-jack.

Regular readers will know that I went through a major re-build on my 3.5 V6 Pajero. This after a "disastrous" head gasket replacement that ended in the wiring loom being damaged and giving timing errors. This was fixed by our very own Carat 3.6 - Simon.

Since that time I have become **** about running temps. To that end I re-cored the radiator, fitted a new rad cap, thermostat, hoses, 50/50 blue anti-freeze, flushed the heater matrix & fitted a new Viscous Fan etc. In summary I re-built the entire coolant system, culminating in a re-gas of the air con.

Now, a Pajero is no different to a Merc. It has an engine that gets hot and uses coolant and a water pump to stay cool.

What maybe different is the ancillaries that affect the coolant temps. In this case I have in front of the main coolant radiator:

An ATF cooler that blocks half the rad.
An AC cooler that blocks the other half of the rad.
These are in turn cooled by a large eight blade electric fan that sits behind the grille and is controlled by the AC Compressor clutch.

All of this means that there is very little direct air flow to the engine rad. What little flow there is saturated with very hot air from the ATF and AC coolers being sucked by the Viscous fan straight through the main engine radiator.

So now I find that with the AC on and blowing 17c and the outside temp at 30+c my engine temps sit at 87>90c until I stop in traffic! At which point they start to climb rapidly!!! Yesterday they reached 110c (on a calibrated temp gauge, that reads from the top hose). When the traffic starts to flow again the temps will slowly drop back to 87>90c

Would the panel say that this is normal behaviour?

Today in my wife's V6 Petrol Wagon. I did the same run with the AC fully on. The temp in traffic climbed to about 101c with the outside temp at 24c.

So the outside temp is about 10c lower than the previous day with the engine temps being about 10c lower. That does seem to correspond nicely?

What worries me here is this. I have no idea what I should expect to see?

Should the cooling system keep the coolant at set temp regardless of ambient outside temp? Bearing in mind that you have a viscous fan on the Pajero with an electric AC and ATF fan (both checked and working) Then on the Merc you have an electric fan behind the rad and in front of the engine.

I have read in the posts on here that 50/50 antifreeze has a boiling point of around 117c?

So I am thinking that what I am seeing in my Pajero at 117c in outside temp of 34c and no air flow (apart from fans) is normal and not a concern. But I don't sleep well on that theory and need re-assurance.

I also see on here that others struggle with the same questions.

Now I fully expect that that 2016 built Merc will be more coolant efficient than than a 20 year old Merc or Pajero. But science remains science and boiling points remain boiling points.

So when should I/we panic and bale out by switching off the engine.

 

[Lyserman]

Pressure also has an influence upon boiling point.
Hence the pressurised system.
Old hoses which cannot take the designed pressure and radiator caps which vent too soon all contribute to overheating issues.

A system should be designed to remove the excess heat before any boiling occurs in the maximum ambient temperature for the region the car is supplied for use in.
Theoretically, when the vehicle stops forward motion and the temperature when the fan cuts in is reached then the temperature should start falling once the fan starts.

If the temperature continues to rise then the system needs to be altered to cope.

The Pajero is an import car, I think, so it may be designed for colder regions than here.

Getting back to your question;
If the temperature continues to rise once the fan cuts in, then I would start to panic.

Tony

 

[Yugguy]

Once warmed up, the C220CDI varies between 75 and 85 indicated depending on outside temperature, or sitting in traffic. Never goes outside those two.

My Focus TDCI before that sat at just over halfway (no scale) and never varied no matter what happened.

 

[brucemillar]

Pressure also has an influence upon boiling point.
Hence the pressurised system.
Old hoses which cannot take the designed pressure and radiator caps which vent too soon all contribute to overheating issues.

A system should be designed to remove the excess heat before any boiling occurs in the maximum ambient temperature for the region the car is supplied for use in.
Theoretically, when the vehicle stops forward motion and the temperature when the fan cuts in is reached then the temperature should start falling once the fan starts.

If the temperature continues to rise then the system needs to be altered to cope.

The Pajero is an import car, I think, so it may be designed for colder regions than here.

Getting back to your question;
If the temperature continues to rise once the fan cuts in, then I would start to panic.

Tony

Tony

Thank you. Regards "the system needs to be altered to cope" I agree that this is likely eventuality. So I removed the rather wafty OEM AC fan, and gave fitted two motorsport electric fans that are using the existing wiring loom, and so the existing switching. That is that they are switched be an earth that is controlled by the AC clutch. In effect they run almost continuously when the weather gets above 24c.

This has had some good effect but still the temps are going up to 110c in stationary traffic.

A thought occurred. Could it just be that in having twin electric fans that are pushing air from the from through the AC rad. This is really just pushing hot exhaust onto the engine rad? So making the problem worse?

My next thought was to remove the viscous and fit a big Kenlowe electric fan on a thermostat?

 

[RichardF]

New cars have a damped gauge to stop people worrying and bothering service depts. So As long as the temp is in the normal operating range (varies from car to car but around 80c-110c)
Then the gauge will stay in the middle, if temp goes to the top of the normal range say 120c then the gauge will shoot up. Not dissimilar to having an engine too hot light.

Older cars gauges reflect the true temp, so the gauge will go up and down with stop start driving, as long as it doesn't go into the red no problem.

 

[markmifsud]

My car seems to get to 85c pretty fast, hot air in the car in 1 mile of driving. And no matter if I have the A/C On or Off, sitting in traffic or on a run, it never moves.

 

[tonysmb]

Do you have a manual over-ride switch for the fans, so you can switch them on earlier in heavy traffic? It would also assist with getting rid of hot air when you wish.

TVRs are subject to very high under bonnet temperatures (fibreglass not being as good a conductor of heat as metal) and whilst the system copes perfectly adequately, many owners, including me, fit over-ride switches allowing a decent air flow across the engine bay as and when required. It's surprising how much heat escapes from the bonnet vents.

If yours isn't UK spec, do the thermostat operating temperatures vary between markets?

 

[brucemillar]

Do you have a manual over-ride switch for the fans, so you can switch them on earlier in heavy traffic? It would also assist with getting rid of hot air when you wish.

TVRs are subject to very high under bonnet temperatures (fibreglass not being as good a conductor of heat as metal) and whilst the system copes perfectly adequately, many owners, including me, fit over-ride switches allowing a decent air flow across the engine bay as and when required. It's surprising how much heat escapes from the bonnet vents.

If yours isn't UK spec, do the thermostat operating temperatures vary between markets?

Tony

I have not fitted an over-ride switch as the fans are on as soon as the ambient temp gets up to around 22c I may just try a switch though.

The stat is a new genuine Mitsi 82c and tested.

 

[markmifsud]

Have you tried checking the actual temperature? I was a bit worried that my temps were out a few years ago but using a lazer temp gun on the top hose confirmed the rad temps were perfect.

 

[brucemillar]

Have you tried checking the actual temperature? I was a bit worried that my temps were out a few years ago but using a lazer temp gun on the top hose confirmed the rad temps were perfect.

Mark.

Thank you. Yes I have checked the temps with an infrared thermometer and my calibrated aftermarket gauge is reading correctly.

 

[tonysmb]

Hmmm, I typed a reply then lost it

When you mention about the fans blowing hot exhaust over the main rad, do you mean the warmer air from the air con unit. If so, that's not uncommon.

Having other rads in front of the main one is not unusual.

The main engine cooling should, I suspect, be cooled by the main viscous fan. Is it pulling air the correct way when it's working? Is it 'locking up'?

Is the water pump working correctly, I didn't see it on the list of replaced items.

I agree with the earlier poster, once the fans are on, the temperature should start to fall. If the coolant temp is 85 and the fan is working, even if ambient temperature is 30, that's still quite a difference.

Has the Pajero been fitted with any off-roading equipment which reduces air flow in or out of the engine compartment, ie winches or under-engine guards.

Is the boiling point you've quoted (117 degrees) at atmospheric pressure?

 

[Lyserman]

Just a quick thought.
Are the fans moving the air in the right direction? Just noticed this is an echo from the post above.
Not wanting to insult your intelligence but the simplest things can sometimes be overlooked.
I know from personal experience, doh!
Are the fins on the condenser bent or clogged?

Tony

 

[190]

Here's one thing that won't be helping the cooling performance.

Is the 50/50 antifreeze mixture correct ? The reason I ask is antifreeze has a lower specific heat capacity than water. In other words strong antifreeze mixtures will not transfer as much heat as weak ones. Bottom line is the antifreeze mixture should only be a strong as needed to provide cold weather and corrosion protection.

 

[brucemillar]

Some great points and questions here. Thank you.

To try and answer:

The electric fans are sucking cold air in from the front which they then push through the AC condenser.

The viscous is sucking air through the rad which it then pushes out into the engine bay.

So all air flow is from front to back.

The viscous is locking up. When cold you can turn it with some resistance when hot it will shred a carrot. It also has the original fan shroud.

The water pump and al belts are new.

I am not losing any coolant.

I have not witnessed any steam despite seeing temps reach 115 on the gauge. The gauge is calibrated and has it sender in the top of the engine. The original gauge sender is now in the top hose.

No off road parts or air blocks.

Antifreeze. Now that is a good question. It will be no weaker than 50/50. It is possibly more antifreeze than water.

My next plan is to remove the heater matrix hose ends. Plug in a garden hose and flush the matrix. That will let me remix the antifreeze.

When the stat opens I can see the coolant pushing across the rad. So I am assuming the new Mitsi 82c stat is good

It only overheats when stationary. So that to me says Viscous or a restriction in the coolant flow. That only leaves the heater matrix as that is an integral part of the coolant system and flow.

Logical?

Sent from my iPhone using MBClub UK

 

[hotrodder]

50/50 water/antifreeze boils at ~ 107°C at standard (14.7psi) atmospheric pressure
Very roughly for every pound of pressure increase the boiling point will rise another 2°

Rad cap pressures vary with different manufacurers but have probably been getting higher over the years as normal running temps have increased due to chasing thermal efficiency etc. I'd imagine pretty much everyone is aiming for at least 85 - 95° with max coolant temps probably in the ballpark of 120 - 130° for most?
MBs from the 124 era have a 1.3 - 1.5bar / 18 - 21psig rad cap. Some later stuff is more like 1.8 - 2.2 bar or upto 30psig

Obviously not really applicable to road cars but FWIW some years back Cosworth F1 said

Currently the V8 runs with around four litres of water in the entire cooling system, including the radiator. This is circulated at about 270 litres per minute by a small, high-revving impeller, which pumps the water out of the engine at 125degC. Water is still believed to be the best cooling medium and the engines run it with nothing more than the addition of a corrosion inhibitor.

quoted from Inside an F1 Engine - Racecar Engineering but then they're allowed to pressurise the cooling system upto 3.75 bar (raising the boiling point of plain water to ~141°C) and don't need to worry about parking outside in winter

If you lower the coolant mix to ~40% antifreeze the boiling point will drop 2 or 3 degrees but, as said, the specific heat capacity will increase a bit. So will thermal conductivity as plain water is about twice as good as ethylene glycol with regards to both. There's tables for freezing & boiling points of different mixture strengths here Ethylene Glycol Heat-Transfer Fluid

Pretty much everything has been said, only thing that's not been mentioned is corrosion in the water passages which mess with heat transfer and Simon would've pointed that out when he was doing the gasket. The only other thing that comes to mind is a cheapnese waterpump but i can't see either you or Simon letting that happen unless there was no choice

 

[brucemillar]

50/50 water/antifreeze boils at ~ 107°C at standard (14.7psi) atmospheric pressure
Very roughly for every pound of pressure increase the boiling point will rise another 2°

Rad cap pressures vary with different manufacurers but have probably been getting higher over the years as normal running temps have increased due to chasing thermal efficiency etc. I'd imagine pretty much everyone is aiming for at least 85 - 95° with max coolant temps probably in the ballpark of 120 - 130° for most?
MBs from the 124 era have a 1.3 - 1.5bar / 18 - 21psig rad cap. Some later stuff is more like 1.8 - 2.2 bar or upto 30psig

Obviously not really applicable to road cars but FWIW some years back Cosworth F1 said
quoted from Inside an F1 Engine - Racecar Engineering but then they're allowed to pressurise the cooling system upto 3.75 bar (raising the boiling point of plain water to ~141°C) and don't need to worry about parking outside in winter

If you lower the coolant mix to ~40% antifreeze the boiling point will drop 2 or 3 degrees but, as said, the specific heat capacity will increase a bit. So will thermal conductivity as plain water is about twice as good as ethylene glycol with regards to both. There's tables for freezing & boiling points of different mixture strengths here Ethylene Glycol Heat-Transfer Fluid

Pretty much everything has been said, only thing that's not been mentioned is corrosion in the water passages which mess with heat transfer and Simon would've pointed that out when he was doing the gasket. The only other thing that comes to mind is a cheapnese waterpump but i can't see either you or Simon letting that happen unless there was no choice

Thank you..

I will try and flush the Matrix today ( I read on the Owners Club that this is a known block).

I will report back.

 

[brucemillar]

Well I removed the in and out coolant pipes to the matrix from the Firewall. Attached the garden hose to the inlet and switched on the hose. No big dramas. It pushed out some blue antifreeze then clear water flowed at the same rate as the hose.

Disappointed at finding no issues, I went to re-attach the inlet pipe. I noticed a very small thread like bit poking out the end of the pipe. Pulled it and out popped a lump of old head gasket. Not a huge lump. But it was trapped in the pipe, so big enough to restrict some flow.

I have re-attached and taken for a 45 minute run with the temps all looking good even when I stopped for 5 minutes it never climbed above 90c.

I am cautious about this so will wait for another good run before celebrating.

FYI: The head gasket was NOT replaced by Simon (Carat 3.6) that was done by the garage who knackered the wiring loom.

One point here:

I left the outlet pipe off and a running hose in the radiator cap. With the engine at idle, flow from the outlet was virtually zero, a dribble at best. With even a tiny amount of revs, the flow shot up pushing water through very quickly. When you shut off the revs you get a surge then back to a dribble. I have no idea if this is correct or not? I tried the same with the rad cap on and no difference. I am guessing that with the pipe off I have no pressure in the system so this may be expected behaviour?

 

[hotrodder]

My bad i forgot Simon took over and sorted out the mess. Lack of pressure in the system shouldn't make a difference, as you say the flow increased with rpm. Dunno where coolant is 'bleed off' for the heater on a Pajero but 124s have a leccy pump to boost flow through the heater... [/glass half full]

Fingers crossed the initial improvement after fishing bits of gasket out will stay. If it doesn't and you get caught in traffic with rising temps again i'd use the throttle to raise the idle speed a nats and see what happens. If things improve i'd be pointing a finger at the new waterpump [/glass half empty] or (extreme long shot?) doing a bit of research into whether Mitsubishi ever made any changes to waterpump pulley size

 

[brucemillar]

My bad i forgot Simon took over and sorted out the mess. Lack of pressure in the system shouldn't make a difference, as you say the flow increased with rpm. Dunno where coolant is 'bleed off' for the heater on a Pajero but 124s have a leccy pump to boost flow through the heater... [/glass half full]

Fingers crossed the initial improvement after fishing bits of gasket out will stay. If it doesn't and you get caught in traffic with rising temps again i'd use the throttle to raise the idle speed a nats and see what happens. If things improve i'd be pointing a finger at the new waterpump [/glass half empty] or (extreme long shot?) doing a bit of research into whether Mitsubishi ever made any changes to waterpump pulley size

Yesterday was another hot day here in Kent. A Huge Truck load of hay caught light and closed the M2 for most of the day/night. About two miles from my house.

I had several runs out and the temps never exceeded 88/90c this includes going up hills and sitting in traffic and the obligatory wait for the wife outside the supermarket.

I do hope that this is the end now. It has been a shocker. Thank you again for all your help and suggestions.

 

[WDB124066]

What, so just the head gasket material blocking the heater matrix inlet Bruce...??