Temperature spike after restart when towing.

[Jwc]

So i have spent about three solid weeks googling for an answer to this including every thread on this forum so forgive me if this seems like a repeat but i dont think it is.

I am towing a 2.3t van with a NP Diesel 2004 auto 185000klms on clock owned from new and always serviced. This is its first long towing trip down from Gold Coast, currently in melbourne having done the scary uphill section from batemans bay last week.

I have had various well known issues in the last two months of travel and had the following work done whilst on the road

* companion shaft popped, replaced seals and c clips, boy that should have been a recall but luck i didnt lose all the diff oil as it was a slow leak not the explosive version

* temp guage spiked when just iddling around town, replaced temp sender and thermostat. Pretty sure that was the thermostat failing not the crazy ivan guage problem as it has been steady since then.

* got very worried about temps whilst at eden about towing up the kings highway so took to radiator repair shop who fitted new radiator and beleive it or not replaced thermostat again but with what is claimed to be a high flow version. The radiator had no blockages but the top tank did look like it had some fatigue/crazing on the inside.

So to the current concern. Firstly towing up the batemans bay road was pretty rough with the guage getting up to just under the red indicator at some points for a minute or two. That could be just the extreme load it was under. However my main issue is that after towing for a few hundred klms and the temp being happilly at the 40% mark the whole time, if i stop for a 5-10 min break, when restarting the guage will move to about 3/4 after about 30-60 secs and stay there for up to 60 secs before taking about another 30 secs to drop back to normal.

I have contemplated the viscous fan clutch possibility but then it doesnt make sense to return to normal so fast. Also the fan seems stiff when cold and no visible signs of leakage. My current thoughts are actually around transmission heat. I am currently towing in 4th and 4H after reading many threads on that. I am thinking the delay on restart in going high is the time it takes the engine oil to pump from the tranny into the radiotor and cause the coolant to spike. As the radiator does its thing it then cools back to normal temperature. I still see this behaviour even if i idle for 15 minutes before turning the motor off and restarting again in 5 minutes.

I am going to try going back to 2H for the next leg and see if that helps on the assumption that maybe the transfer case is causing extra heat.

Anyone had simmilar experience or suggestions ? I usually travel right on the 100km acording to dash which gps actually says is 94km/h.

Thanks for any help.

[spot01]

As you have done a lot of research on the forum, you are probably across all the possibilities, but here is a summary of the possible issues I can remember re the Gen 3:
- these cars don't usually run hot unless there is something wrong (especially if it used to be OK)
- faulty part (resistor?) in the instrument cluster giving false temp readings (have you done this repair to rule it out?)
- Viscous fan appearing OK when stopped, but not actually working properly when running (this has tricked quite a few people & these viscous coupling don't appear to last forever) - if your car has an electric fan in front of the radiator for the A/C, try running the A/C (to make this fan run) to see if the temp behaves better (if so, may indicate the belt fan is dodgy). You should be able to hear the belt fan roar at higher revs if it is working properly when the temp is up. Are the belts fairly new & correctly tensioned?
- thermostats that are not behaving correctly (either faulty, installed incorrectly or the wrong unit for the car - has the current concern only appeared since the last thermostat replacement?)

It is normal for an engine to get hotter when turned off, then cool down when restarted, although the gauges generally don't show this, as they have a large mid temperature range where they don't alter (to avoid worrying us drivers, apparently).

I wonder if you may have more than one issue going on, but I'd probably focus on the hot running when climbing hills & the cooling system first, particularly the fan. I think the transfer thought doubtful & in any case, MMAL recommend towing in 4H, not 2H. If you think the transfer is getting too hot, check the oil level & condition perhaps?

[nj swb]

So to the current concern. Firstly towing up the batemans bay road was pretty rough with the guage getting up to just under the red indicator at some points for a minute or two. That could be just the extreme load it was under. However my main issue is that after towing for a few hundred klms and the temp being happilly at the 40% mark the whole time, if i stop for a 5-10 min break, when restarting the guage will move to about 3/4 after about 30-60 secs and stay there for up to 60 secs before taking about another 30 secs to drop back to normal.

I have contemplated the viscous fan clutch possibility but then it doesnt make sense to return to normal so fast. Also the fan seems stiff when cold and no visible signs of leakage. My current thoughts are actually around transmission heat. I am currently towing in 4th and 4H after reading many threads on that. I am thinking the delay on restart in going high is the time it takes the engine oil to pump from the tranny into the radiotor and cause the coolant to spike. As the radiator does its thing it then cools back to normal temperature. I still see this behaviour even if i idle for 15 minutes before turning the motor off and restarting again in 5 minutes.

I am going to try going back to 2H for the next leg and see if that helps on the assumption that maybe the transfer case is causing extra heat.

Anyone had simmilar experience or suggestions ? I usually travel right on the 100km acording to dash which gps actually says is 94km/h.

Thanks for any help.

I doubt that your issue is anything to do with your transfer case - I would continue to use 4H.

You don't mention if you use manual mode, or leave it in auto while you are towing.

Towing in auto can produce very high transmission temperatures, as the transmission invariably hangs on to a gear too high. It could be your transmission fluid causing the spike on restart, rather than your engine oil (I'm presuming the transmission oil passes through the bottom tank of your radiator).

If you're already using manual mode to change gears this is unlikely to be your problem - unless you're "towing in 4th", which can also result in too high a gear. These autos aren't smart enough to make all the right choices while you're towing - often, you need to choose the right gear for it.

[erad]

The phenomenon about the gauge rising and then falling is called heat sink. It is normal, although it is not usually noted by owners. Remember that the gauge is not linear. Zero to 40% would be a range of 20 to 75 Deg C. The 50% mark is about 90 Deg C and the red line is probably about 105 Deg C, so what look dramatic is not as bad as it seems.

I would check your fan coupling. The drag up the Clyde Mountain is mean and tests any cooling system, but your coupling may be a bit weak. Check it with the engine at operating temperature. Stop the engine and the fan should stop almost immediately. Feel how much drag then. It should be stiff, but still able to turn the fan blades by hand. I had a stuffed coupling on my Range Rover years ago, and I could CAREFULLY place my hand into the blades whilst the engine was running and stop the fan. You could try doing this if you suspect the coupling by using a piece of wood to stop the blades. Naturally, keep your hands well away from the blades, and don't just shove the wood into the blades - lay the wood against the surface of the blades and try to stop the fan that way.

[Jwc]

Thanks for the reply spot,

- “Use to be ok” is hard to confirm as this is the first time it has really been asked to tow. To clarify that the van is tare 1900 and loaded 2300kgs. When not towing i do not see the problem of hot on restart though i will tripple check that on a trip today.

- i havent done the resistor repair yet, have had the dash out previously to put leds in when some gear lights stopped working. I guess i ruled this out on basis of not occuring except when van hooked up, although now i guess the van electrics could come into play on that.

- the viscous fan clutch problem is still on my mind though why it recovers so quickly after spiking when i am stationary would indicate the clutch is operating pretty well. I do understand these things age and slow down/slip more. On that, reading replacements i cant get a good read on if the dayco part is worth using at $250 ish or pay the ransome of $500 for the genuine part. Threads seem to differ on whether the dayco ever cuts out. Will probably look at genuine.

- since last thermostat replacement i can’t remember to be honest. I seem to recall it still heppening once or twice on the first replacement which was a genuine MM part and service centre 3 weeks ago.

Oil levels havent changed it never uses any and when radiator was replaced the trans oil coming out was in good condition. Will check again now after the kings highway trip. To be clear on the temp when running, from yass to albury down the hume it never climbed above middle whilst running and there are some reasonable inclines there. It did slow to 80klms at times in 4th necesitaating me to go back to 3rd.

Again thanks for the thoughts.

[Dicko1]

Thanks for the reply spot,

- “Use to be ok” is hard to confirm as this is the first time it has really been asked to tow. To clarify that the van is tare 1900 and loaded 2300kgs. When not towing i do not see the problem of hot on restart though i will tripple check that on a trip today.

- i havent done the resistor repair yet, have had the dash out previously to put leds in when some gear lights stopped working. I guess i ruled this out on basis of not occuring except when van hooked up, although now i guess the van electrics could come into play on that.

- the viscous fan clutch problem is still on my mind though why it recovers so quickly after spiking when i am stationary would indicate the clutch is operating pretty well. I do understand these things age and slow down/slip more. On that, reading replacements i cant get a good read on if the dayco part is worth using at $250 ish or pay the ransome of $500 for the genuine part. Threads seem to differ on whether the dayco ever cuts out. Will probably look at genuine.

- since last thermostat replacement i can’t remember to be honest. I seem to recall it still heppening once or twice on the first replacement which was a genuine MM part and service centre 3 weeks ago.

Oil levels havent changed it never uses any and when radiator was replaced the trans oil coming out was in good condition. Will check again now after the kings highway trip. To be clear on the temp when running, from yass to albury down the hume it never climbed above middle whilst running and there are some reasonable inclines there. It did slow to 80klms at times in 4th necesitaating me to go back to 3rd.

Again thanks for the thoughts.

Have you actually put the van and the car, when fully loaded, onto a weighbridge? If you are only assuming ......weights could be a lot higher than expected.

[Jwc]

Thank nj,

I am towing in manual and i do try not to let it labour in 4th slipping back to 3rd if it gets to around 80kms. On those 25km turns on kings highway it was in 2nd and back to 1st when temps started to scare me.

I do not that sometimes in 4th maybe i am holding it too long as i notice the rpm will increase at times which i guess has to be the torque converter slipping to give more power ? Also when i did tow in auto once it seems to rev up to 4000 before switching from 3rd to 4th where as i tend to change at 3000. Maybe i am being too gentle on the shifts and putting extra load on the tranny ?

Also yes the tans oil runs through the radiator on mine and i have an extra trans radiator it passes theough which i think got added as part of the 2500kg tow pack fitted as an option when new.

[Jwc]

Dicko you are of course correct on that. I am estimating and should put it on a weigh bridge. I am a bit of an anal personality though and have weighed the individual bits put in van and dont carry water if not necessary. However who is to say the tare is accurate as plated ? Will get it weighed.

Good thought

[spot01]

Another thought - do you have anything partly blocking airflow to the radiator, eg, insect screens, lights, bars, etc? If so, might be worth trying to remove what you can - it all helps when things are marginal. Is the A/C condensor clear of bugs, mud, etc?

Re the fan, it may be OK at low revs but not at high revs perhaps? When you first drive the car cold, you should hear the roar loud & clear until it drops out soon after - does it roar when the temp is up on the hills (window needs to be open)?

[Jwc]

Thanks Erad,

I have noticed all you posts on the fan clutch issues on other threads, much appreciated, all of them. As the clutch is now 14 years old i think it has the right to have probably slowed a little :-) I see on the dayco site the refer to them losing 200 rpm a year ! I suspect mine hasnt failed but may well have slowed a significant amount due to oil age. I suspect that will be my next action anyway. I am also going to get a performance tune on the ecu. At the very least that will turn off the egr valve which could also help temperatures in general ?

[Jwc]

Spot, nothing added to grill on my car it is virginal in that respect. No debris in any radiators or grills.

The clutch remains best bet again i think as i dont notice a change in noise after running for a while. I suspect mine is always engaged but slipping due to age as it is stiff. I tried to get radiator guy to check it before doing anything else but of course there 90% case is radiator blockage and he couldnt get a clutch at short notice anyway.

[Jwc]

Just a quick note on fan clutch. Mine does slow after about 3 mins from a cold start. Its not that load on start but i can feel significant air flow behind the fan then after 3 mins a noticeable decrease in air flow. I am wondering if my problems are just due to aging and extra slip of clutch vs any valve failure in it. If the dayco site is right an a reduction of approx 200 rpm per year is even close to correct then i must have lost at least 1000 rpm over 14 years and since they start with a design of 70% of flywheel rpm when “locked” or 2100 at 3000 engine rpm, i would have lost significant cooling when it is most needed.

Now its just a case of doesanyone think the genuine MM part is worth the extra premium ?

Thanks again to all

[spot01]

Just a quick note on fan clutch. Mine does slow after about 3 mins from a cold start. Its not that load on start but i can feel significant air flow behind the fan then after 3 mins a noticeable decrease in air flow. I am wondering if my problems are just due to aging and extra slip of clutch vs any valve failure in it. If the dayco site is right an a reduction of approx 200 rpm per year is even close to correct then i must have lost at least 1000 rpm over 14 years and since they start with a design of 70% of flywheel rpm when “locked” or 2100 at 3000 engine rpm, i would have lost significant cooling when it is most needed.

Now its just a case of doesanyone think the genuine MM part is worth the extra premium ?

Thanks again to all

Don't know, but I think a few formites have shared their experiences re Dayco &/or other brands, so some searching may help shed some light (use Google, not our search engine).

For me, amounts like $250 or $500 seem to evaporate from my wallet so frequently these days that I'd probably go genuine unless I was totally confident in the after market part. More times than I car to remember, I've bought a cheaper &/or non genuine something, only to end up buying the more expensive one later & therefore wasting money I was trying to save, not to mention the value of the asset you are trying to protect in this case.

PS - ask MMAL for "trade price" - it often helps.

[Jwc]

Hmm well apparently the wait time is 3 weeks when ordering from an albury dealer. Not sure i can be here that long. I suspect you are correct on genuine vs after market.

Can i actually ask for trade price if not a mechanic ? Or is it given under the assumption you will be getting it installed when asking that price ?

Again thanks for all the help

[Dicko1]

Dicko you are of course correct on that. I am estimating and should put it on a weigh bridge. I am a bit of an anal personality though and have weighed the individual bits put in van and dont carry water if not necessary. However who is to say the tare is accurate as plated ? Will get it weighed.

Good thought

I always assumed that my camper trailer weight on the draw bar was about 100-120kg. I added a boat rack, 3.7mt tinny and 15hp 2 stroke ...ball weight went to 220. since moved things around and back to 140kg now. this is only ball weight. when project is finished I will get everything weighed at the local tips weighbridge. I would be very surprised if the tare weight stamped on the vin plate is accurate. I,d expect 2-300kg more at least..