Engine Coolant Temperature Ranges

[tomo88]

Assuming 4th on rpm as it does feel like it gears down once on level ground and will check auto temps if available on obd tool as well tomorrow

[spot01]

Assuming 4th on rpm as it does feel like it gears down once on level ground and will check auto temps if available on obd tool as well tomorrow

You may just be seeing the torque converter unlock rather than a downshift - flick it to manual to see what gear it is in.


Having said that, I leave my NX in D going up there with no dramas at all - gauge never moves. Different model but yours should do it easily.

[twisted32]

Assuming 4th on rpm as it does feel like it gears down once on level ground and will check auto temps if available on obd tool as well tomorrow

Yeah use manual mode, and monitor trans temps as well. I suspect you are 5th unlocked dumping lots of transmission heat into the coolant.

I use that climb for testing on mine on hot (40deg) days, with all my mods, in 4th locked, it will normally just crack 100deg coolant temp at crafers. In the morning at 20deg ambient, it should not be hitting 117deg.

If you prefer to drive it in auto, look at auto mate from MM 4x4.

[tomo88]

So measured core and was 26mm, checked hosing. Once again this morning up to 117 degrees before the hills begins to taper off. This time though, I put it into manual and it did say it was in 5th, so I will definitely try it in 4th tomorrow morning and suss the results. I have noticed since the timing chain it feels like it's less indecisive when choosing gears. So to clarify in 5th it'll be working harder because there's more torque on the gearbox, just like trying to pedal uphill on a bicycle in higher gears/lower ratio? By putting it in 4th, takes more load off the gearing but uses more fuel, which would be better overall for the system? It's just odd because I never drove it in manual before all the work done and after the work done these things are happening now. The mechanics suggested the system may be getting more fuel now because of the timing chain change as an explanation for the hotter engine. Unfortunately, the trans temp isn't an option I can find on the obd app but as you mentioned, the coolant temp should reflect this

[spot01]

So measured core and was 26mm, checked hosing. Once again this morning up to 117 degrees before the hills begins to taper off. This time though, I put it into manual and it did say it was in 5th, so I will definitely try it in 4th tomorrow morning and suss the results. I have noticed since the timing chain it feels like it's less indecisive when choosing gears. So to clarify in 5th it'll be working harder because there's more torque on the gearbox, just like trying to pedal uphill on a bicycle in higher gears/lower ratio? By putting it in 4th, takes more load off the gearing but uses more fuel, which would be better overall for the system? It's just odd because I never drove it in manual before all the work done and after the work done these things are happening now. The mechanics suggested the system may be getting more fuel now because of the timing chain change as an explanation for the hotter engine. Unfortunately, the trans temp isn't an option I can find on the obd app but as you mentioned, the coolant temp should reflect this

Mechanic is talking BS, IMO. I think you need to find a new mechanic, when this is over, or perhaps before? Wright Street Automotive get a good wrap on here (no association).

[Merts]

So to clarify in 5th it'll be working harder because there's more torque on the gearbox, just like trying to pedal uphill on a bicycle in higher gears/lower ratio? By putting it in 4th, takes more load off the gearing but uses more fuel, which would be better overall for the system?

Not really. In certain conditions the torque converter will unlock in 5th rather than the box downshifting to 4th. The slipping converter produces heat and it's often more economical to manually downshift to 4th.
I've driven up the hill you are talking about quite a few times in my old NS, and I would definitely manually select 4th rather than let the auto slip in 5th.

"The mechanics suggested the system may be getting more fuel now because of the timing chain change as an explanation for the hotter engine. "
Your mechanic is full of 'it'.

[tomo88]

Over the last couple mornings, I have been running it in 4th as suggested and it seems to have made a significant difference. It will now just get to 99 degrees celcius at the top of the hill just before the Crafers turn off. The ambient temperature compared to monday was 12 degrees in the morning as opposed to 20 degrees but surely that would not cause that significant a difference?

I did a bit of research of torque convertors and how they work, as well as looking into the MM 4x4 auto mate videos of why the heat is caused and it makes heaps more sense now.

Thanks very much for all the assistance to everyone; I don't understand how the timing chain and tappets would have impacted the gear selection but I guess it did. I noticed the auto was more hesitant before hand. I'll continue to monitor coolant levels as well.

[spot01]

Still sounds odd to me - try to repeat the test at the same weather conditions. Also try the test on a really hot day to see what difference there is - if it stays the same it may just have an incorrect thermostat in it.

In any case, it should cruise up there easliy when empty in D with no dramas, even on very hot days. Even heavily loaded or towing a heavy load, it should still be OK. These cars are usually very good in these conditions.

Note there is a auto trans fluid cooler in the bottom of the radiator, so they would have meddled with that also - check trans fluid level & condition.
Unsure if your car has an electric thermo fan as well as the belt driven one - if so, check it is running correctly, eg, it should run when a/c is on or when the car is above normal operating temp. Check wiring/plug in case they messed it up.

[Merts]

In any case, it should cruise up there easliy when empty in D with no dramas, even on very hot days. Even heavily loaded or towing a heavy load, it should still be OK. These cars are usually very good in these conditions.

It will do it, but a slipping torque converter will produce heat. It's not great practice to let it do it for an extended period.

Bear in mind too that the OP's vehicle is an NS which has the older transmission (I think it was a Jatco) as opposed to the newer models which have a far superior Aisin box.

[erad]

I have been watching this thread with interest. To my way of thinking, everyone is focusing on the transmission, but there is still a fault with the cooling system. Yes - a slipping torque converter will cause extra heat, but the cooling system should still be able to cope with this without the gauge going that high.

The gauge is not linear in its operation. I checked my NW (manual transmission) the other day and the Scangauge was telling me the temperature was 66 Deg C and the needle on the gauge was about the thickness of the needle below the mid point. Mid point is 88 to 90 Deg C, and under really heavy loads I have seen it go to 98 Deg C. At that time the needle was barely above mid way on the gauge. the highest I have seen the gauge has been about a needle width above mid point. One or two degrees either way does not matter, but I think you are well above what is normal.

[old Jack]

The NS with the Jatco VA5A auto has a relatively low torque convertor slip ratio of 1:1.6 so the trans will change down earlier than the PB/PC Challenger which has the same VA5A auto and gear ratios but a higer slip 1:2.04 slip ratio. The only time I have every seen the ATF high was 116C whilst towing a 3,000kg trailer up the SE Freeway and a 36C day, the Challenger was down to 53kph and 2nd gear in sport mode by the time I got to the top of the climb at Crafers. 3,000kg towing capacity what a joke!

The Jatco Auto in the Ns will lock the torque convertor in 3rd, 4th and 5th gears but you need to match the speed to the rpm to see if the TC is unlocked. Often by easing off the accelerator the rpm will drop but not the speed, this is because you are reducing the amount of TC slip.

As a guide here are some gears, speeds and RPMs when the TC will be locked, if the rpm is higher than what is listed for the gear selected then the TC is slipping and heating up the ATF quickly. I used this as guide before I had Lockup Mate or Auto Mate and I found it kept temperatures down about 10 to 15C whereas with Lockup Mate and Auto Mate the temperatures are down by 20C to 40C under the same conditions.
The following figures are based on factory diameter tyre's.

3rd 60kph 2280rpm
3rd 70kph 2660rpm
3rd 80kph 3040rpm
3rd 90kph 3420rpm

4th 70kph 1880rpm
4th 80kph 2140rpm
4th 90kph 2410rpm
4th 100kph 2670rpm
4th 110kph 2940rpm

5th 90kph 1750rpm
5th 100kph 1950rpm
5th 110kph 2150rpm

OJ.

[rotare]

I've lived in the Adelaide hills for decades and drive up and down the freeway daily. I've had a scangauge on my NW Paj since I've owned it so I'm familiar with what to expect in regards to inlet, trans and water temps.

Generally, with ambient temps up to about 30C my radiator temp will be around 90-91C by the time I get to Crafers. That's driving in 4th gear and at the 100Km/hr speed limit.

Above 30C ambient temps and driving in 4th at the speed limit the radiator temps would be in the low to mid 90's, but no higher than 95-96C, regardless of ambient temps.

The other week when it was 42C (?) I was in a rush to get home and drove faster than I normally would up the hill in 5th gear, but the trans was locked. By the time I reached Crafers the radiator temps just peaked at 100C, but rapidly dropped to about 84C once over the hill, and the temps stabilized at around 89C.

If you're familiar with the hill out of Cape Jervis (it's steep!), I often tow my 2.5T boat up there, with three passengers in the middle of a summers day. That's a third gear slog, foot buried on the pedal, from the bottom of the hill to the top, probably pulling 60-70km/hr at the most. Highest radiator temps I've seen in that situation 106C..... but that's an extreme example.

Long story, but if you're seeing 117C anytime, particularly so if the ambient temp is mild, in my opinion you've got problems with your cooling system.

[tomo88]

Its good to have those base line numbers to work with, rotare. thank you. I went and saw the mechanic today and he was adament that everything on their half was double checked and good to go. I have been missing my fan shroud since purchasing the vehicle and he stated that that may be the issue. Also, he noted that prior to the timing chain and clearances the engine may have been retarded and not stressed the engine as much as is. But it seems like the general consensus, even when I told him that it tops at 100 at Crafers now, is that its still too hot. I've hit up a wreckers and am picking the shroud up tomorrow and will install it over the weekend. Hopefully doesn't require the removal of the radiator; I've tried to google a few gigs. Though my understanding is the fan is not even active at highway speeds?

[old Jack]

Having a look at the wiring diagrams there appears to be only 1 coolant temperature sensor that generates the signal for the dash gauge, engine ECU and the OBD2 port. So my thinking is what happens if this sensor is giving the incorrect signal?

Have you checked the actual coolant temperature with a thermometer and compared this to the OBD2 Scantool reading?

OJ.

[erad]

Tomo88:
If you are missing some or all of the fan shroud, this could well be the cause of some overheating. Without the shroud, the fan can draw air in from behind the radiator, thereby not getting air through the radiator (and thus cooling the coolant). Get a shroud fitted and see if that helps.