3.6 TDV8 bad overheating on hills towing caravan

[Graeme]

My brother's MY08 3.6 has badly overheated when towing his 2-2.5T Jayco uphill for the 4-5 years he has owned the car. The temperature gauge needle cannot be made to move off normal without the van attached but any decent hill even on cool days causes overheating, to the point of boiling it on a 23 deg day a week ago. It does not overheat on level ground. It does not use any of coolant.

Temperature probes have been fitted to the top and bottom radiator hose connections. An IIDtool is used to monitor coolant temp, fan speed and duty cycle for some time now, with the fan seeming to behave as it should. Just prior to the first stage power restriction where max revs is 3000, the top radiator temp was 113 and the bottom 103 and the IIDTool showed ECT 113. 2nd stage restriction limits revs to 2000 rpm. It boiled close to 120 as there was nowhere to stop part-way up the hill. Overheating very quickly escalates from mildly warm to excessively hot in a very short time.

The thermostat was removed after the boiling but while the engine ran too cold, it still overheated uphill with the van. The thermostat bypass valve was found to be split and otherwise damaged preventing it from closing so a new thermostat housing was fitted 2 days ago but overheating persists.

There appears to not be any mud or debris between the i/c and coolant radiators, as water squirted backwards emerges clean from the i/c and from below the radiator pack.

The water pump is next to be removed to be checked and a new one fitted regardless of apparent condition. next will be the radiator pack which requires the a/c system to be drained.

Are these vehicles prone to overheating when towing? I can't find any reference to overheating where coolant is not being lost.

Any suggestions?

[Pedro_The_Swift]

I suppose both the rad and pump are now 8 years old,, not at the age where you could just point the finger, but,,, maybe the two parts combined are not up to scratch?
if the car is staying in the family probably worth the ( both) replacement cost.


Like you I have not read of there being an overheating issue, in fact this may be the first one!

[Graeme]

Unless the impellor has detached from the shaft, I doubt the pump will be the cause but it's easy enough to replace and has now done 200K anyway. With older generation vehicles a blocked radiator would be suspected especially if cross-flow as in my RRC but this alloy, top to bottom flow radiator without scale problems of cast iron blocks and copper radiators should not suffer the same problems. The vehicle only had 60K when bought yet has always overheated with the van.

I've suggested a run up a local big hill using Sport mode without any manual gear selection to see how gear selection and engine revs compare with how he normally drives in case he's overloading the engine by not allowing it to rev high enough.

[Pedro_The_Swift]

its beginning to sound like a design issue, not a worn parts one.

[Blade74]

I suppose both the rad and pump are now 8 years old,, not at the age where you could just point the finger, but,,, maybe the two parts combined are not up to scratch?
if the car is staying in the family probably worth the ( both) replacement cost.


Like you I have not read of there being an overheating issue, in fact this may be the first one!

10 years old now.
Has the water pump ever been replaced?
Mine was done after 9 years.
Not that it ever overheated.
I just had the thermostat housing replaced and a lot of hoses recently.
I don’t have any solutions but will throw out some general questions.
Is it missing any of the plastic cowls. Not sure how critical they are to air flow.
Eg under the motor.
Has it had any other issues that might relate back to it?
Does he have any type of spotlights or aftermarket bullbar?(although I don’t think there are any available).

[Graeme]

Note my added comment about gear selection. My 4.4 TDV8 needs 1st gear to climb a particularly steep pinch near Talbingo with my 2.5T van at about 40 kph around hair-pins but my L322 is excessively highly geared and made worse by nearly 32" tyres instead of the original 30".

[Graeme]

Water pump is expected to be the original but as the overheating existed when purchased with 60K kms, unless the water pump has always been faulty then its not likely to be the cause but will be replaced anyway.

A short light bar had been fitted but has since been removed. No bull-bar is fitted.

No other issues.

It is possible that the original owner had the ecm remapped but no soot accumulates on the van and fuel consumption is better than a friend's diesel Paj pulling about the same weight van, suggesting that the ecm is original.

A flap in front of the radiator that might move at speed has been cable-tied away to ensure that it can't restrict airflow.

I've suggested removing the gearbox under-tray in case it is restricting airflow from the engine bay.

[Blade74]

It amazes me how hot they get under the bonnet when they arent overheating.
Must be crazy hot when they overheat.

[Blade74]

Could the fan belt be slipping?. I suppose you would hear that.

[Blade74]

I’m assuming the transmission would get very hot when towing that weight.
Not sure how they cool the transmission?
If it’s just an normal oil cooler.
Could the transmission heat be transferring a lot back into the motor/engine bay as well?

[Graeme]

The gearbox has its own oil to water cooler. The gearbox temp hasn't been monitored to date but will be for the next test.

The fan roars as temperature rises. The IIDtool shows the fan rpm which can at times exceed engine rpm.

I wonder if he's working the engine too hard at mid revs rather than allowing it to rev higher in a lower gear although I would not expect it to overheat.

[rar110]

The only time my L322 has got hot was on a hot day during about 30 min of soft sand driving (high tide) in low range. I ended up stopping and letting the engine idle for a bit with the bonnet open.

I’ve never towed anything near 2.5T with my L322, only a couple of types of loaded hard floor campers.

I agree with Blade, the motor emits a lot of heat during normal operation. I took this to mean the motor is efficient at dispersing heat. I have wondered whether additional vents at the sides of the bonnet would be worth while. The shark fin vents are already pretty substantial.

[Blade74]

Is it worth trying to flush the cooling system somehow and make sure there isn’t any sort of sludge built up.
Sounds stupid but you never know.
Mine always appears like the coolant is perfectly clean.

When you drive the car Graeme does it feel like your 3.6?
As in does it feel similar in power?
Just trying to work out if it’s got some issue and having to work harder to achieve the same power.
I also agree that maybe he needs to keep it reving more to keep the fan spinning faster.
But that also may mean turbos spinning faster and more heat being generated as well?

[Blade74]

It would be good to attach the van to another 3.6 l322 and do the same hill test.
That would answer all questions very fast.

[Graeme]

The coolant has been renewed several times.

Mine is a 4.4 L322 so quite different to a 3.6 RRS and I haven't driven his RRS anyway.

He test-drove my 3.0 D4 with the van attached before buying the RRS to see how well the D4 towed compared with his LS-equipped RRC. At the time he commented how the D4 didn't particularly like maintaining speed on a steep nearby hill although I thought he was asking too much of the engine. The D4 dropped gears until revs were rather high then maintained a slower speed. I would have dropped more speed to lower the revs. He's too far away to go for a run with him to see how he manages speed and revs.

[Graeme]

Higher revs won't necessarily turn the fan faster as the ecm reduces the fan clutch engagement to avoid excessive fan rpm. Higher revs won't necessarily increase turbo heat either, indeed often reducing the heat generated as less boost is required for the same power o/p and less unburnt fuel exits the cylinders thus reducing combustion within the turbo. What does increase is the water pump speed which should increase flow through the radiator to some extent. However the impellor design is very open and more a high volume at low pressure than a high pressure pump so less able to overcome hose and fitting restrictions and therefore may not circulate fluid any faster at higher revs.

[Graeme]

Well it seems that the problem has not always existed. My brother now recalls that it did not originally overheat and that it is getting worse. He used to be able to pass slower van-pulling vehicles up hills with ease whereas now it wont go up slight inclines without getting hot. This is good because it changes from a possible design short-coming to something that is no longer working properly so is fixable - water pump or radiator hopefully.

[Ean Austral]

Not sure if it can happen on coolant hoses , but any possibility one of the hoses is collapsing under the extra load and restricting coolant flow ?

Remember the turbo hose on my TD5 did that when towing a caravan and it lost all power, never happened when the van wasn't hooked on , different hose but anything is possible I guess

Cheers Ean

[Eevo]

i'll go with clogged radiator

[Blade74]

I didn’t realise it was a RRS you were taking about as I use Tapatalk and it just appeared on my feed.
I do know that the 3.6 tdv8 is even more cramped in a RRS sport and does heat up a little more than a Vogue.

[Gregz]

It would be good to attach the van to another 3.6 l322 and do the same hill test.
That would answer all questions very fast.

.... and/or attach same car to different caravan - maybe there's something wrong with the caravan, like brakes on all the time.

but I am also going for clogged radiator or collapsing hose (I have had both before on different cars) .

No oil visible in coolant , I hope?

[Graeme]

No oil in coolant or coolant in oil so appears confined to a coolant problem.

Dragging brakes has been discussed but the combination rolls easily along on very light throttle with good economy and burnt linings would have been smelt each time he has had to pull up to cool.

The vehicle has travelled several remote and sometimes muddy tracks in WA and SA towing a camper trailer so mud caught in the fins is very possible even though hosing from the back hasn't revealed any mud.

The RRS engine bay is more cramped than the L322 with the same engine plus the RRS's active roll-bars add congestion behind the engine but since realising that the overheating did not initially occur, I expect that he will find the radiator is either externally or internally partly blocked. It has the same 2-radiator arrangement as the L322 so would be expected to handle some load.

[Graeme]

Today's update - water pump and radiator removed for inspection.

The water pump looks to be as new. The main radiator was clear both inside and outside and back-flushing the radiator produced nothing. The aux radiator was removed and inspected just before Christmas and it too was spotless both inside and out.

Have to check the main hoses for internal delamination/collapsing as suggested.

Whilst the hoses haven't specifically been inspected for delamination and that they appear to be in good condition, its a good time to fit new ones and keep the old ones as spares, unless of course the overheating is overcome with new hoses. Coolant volume through the radiator increases as the need to dissipate heat increases and the increased flow could cause an internal split to be picked-up to at least partially block the hose.

[rangieman]

To me it seems more like a fan problem air flow when working hard .
I don`t know what type of fans they run on these but typically a car will over heat with a crook viscous fan working hard up hills [bighmmm]

[theelms66]

Internal radiator inspection. You can only be sure it is clear by removing tanks.

[Graeme]

The fan is driven by an ecu-controlled viscous coupling. The IIDTool reports both the fan speed and the pwm duty cycle for the coupling drive and both increase and decrease as expected for an engine that gets hot very quickly. All indications are that the fan is turning as required.

It appears that delaminated radiator hoses causing hose blockage is commonplace on vehicles generally as hoses weaken with heat/age. The sudden onset of overheating when this engine is worked could easily be explained by a hose becoming blocked as coolant flow through the radiator increases. Often the tell-tale sign of an affected hose is very slight weeping from the ends around the fibrous material due to coolant having worked its way from the split along the fibres. Obviously the top hose gets the hottest so more likely a culprit than the lower hose.

[Graeme]

Internal radiator inspection. You can only be sure it is clear by removing tanks.
Can't R&R the plastic tanks on an alloy radiator but high volume flushing into the outlet showed no significant restriction. The quick escalation to overheated would require a high percentage of the tubes to be blocked, which is not supported by the flush test.

[theelms66]

On your Original post you said top radiator temp was 113 and bottom was 103 . Sounds a little hot returning into the motor does it not . I dunno.

[Eevo]

On your Original post you said top radiator temp was 113 and bottom was 103 . Sounds a little hot returning into the motor does it not . I dunno.


i was thinking the bottom was a bit hot gien that it was just cooled by the radiator. hence why i think the rad cooling performance is minimal.

[Ean Austral]

Is it possible the cap on the header tank is faulty, not sure if it would make the car overheat without loosing coolant but for $20 which is what mine cost to replace would be a cheap thing to replace just to rule it out.

Cheers Ean

[Graeme]

My brother has been convinced by a radiator place that the radiator is most likely to blame and as a new genuine only costs $600 he's now trying to get one ASAP. He's been offered a slightly cheaper non-genuine version but doesn't know the brand.

The system hadn't been loosing coolant during all the previous overheating events so the cap must be holding pressure.

[Blade74]

For $600 I’d stay original. Not worth changing in my mind.

[Graeme]

Same opinion everywhere! None in AU so waiting to hear a firm time instead of the 1 week guess for LR to get one from the UK.

Fortunately my brother has 3 vehicles so 1 in sick bay for a week doesn't bring him to a stop, unlike me who only has 1. Yesterday I thought I'd have to walk 8 kms to the PO then back again when I had poked a hole through the old oil filter with a screw-driver to remove it from the cap then found that the replacement was shorter. Fortunately the spare was indeed the correct filter but that I had been confused when a NRV assembly in the filter housing cap had un-clipped and stayed in the old filter making the new filter appear shorter.

[fredd63]

On your Original post you said top radiator temp was 113 and bottom was 103 . Sounds a little hot returning into the motor does it not . I dunno.

Only found out recently, 10C is the correct difference top to bottom in a radiator, so it would appear to be working correctly.

[fredd63]

Before you change radiator, try running straight water without coolant. This site has some good info about cooling.

Motor Coolant Selection to help Overheating Engine (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Engine%20Cooling%20Pg7.html)

[Graeme]

He was running 50% which I suggested was too high considering the overheating. I only ever use 30% but straight water would have been a worthwhile test.

A new radiator, water pump and top hose have been ordered. I doubt that he wants to now go to the effort of putting the old radiator back in to try straight water as he separated the radiator pack in-situ rather than drain the a/c system. I'll pass on the suggestion and link.

[p38brickus]

I own a 2008 TDV8 RRS and tow a 25 foot Jayco Sterling topping the scales just under 3 tonne. I've never had an overheating problem with it. It's done nearly 190,000 kms at this stage. 2016 we went from East Gippsland to Qld right up to Cooktown with all the attendant hills and mountains climbed without incident. Last year we went to Darwin and back down the highway turning left at Three Ways and crossing the Barkley Highway to Townsville and up to the Ingham area. We came home via Mount Morgan which is a particularly steep climb. We've just got home from a month up the Sapphire Coast from here. If my car was going to overheat it has had plenty of opportunity to do it towing our van. I tow at about 100km/h up hill and down dale, in fact when the car smells a hill it wants to accelerate up there. It's a beast for hills.
Now, I'm no mechanic so don't shoot me when I make this statement. The fan is behind the radiator and hence helps pull air through the radiator I assume. Is it possible that the fan itself could have been removed from the viscous coupling at some stage and been put back on back to front? I don't even know if that is possible but it's a thought. The radiator may be capable of handling normal conditions without the van and without the fan assistance but when towing the van and adding uphill to the equation, could be too much for the system.
Good luck with it.

[Graeme]

Whilst my brother initially though that the engine had always overheated, he then recalled that it had not as he recalled the ease with which it pulled the van up hills at speed, regularly overtaking slower vehicles.

The fan is detached from the engine by unscrewing the hub assembly and the fan is never detached from the hub, so the fan blades cannot be fitted back to front. However I will pass on your comments and suggestion.

New genuine radiator, water pump and top hose were fitted Monday with the job expected to be finished yesterday but I haven't heard if the car is back on the road yet. The current hot weather will provide a good test.

[Graeme]

The overheating problem has shown to have been resolved, with the old radiator being blamed. No sign of overheating climbing hills at freeway speeds in 40 deg heat. The RRS and van are already on a short trip before holiday time runs out.

My brother thanks everyone for your suggestions.

[Eevo]

open up the old rad and take a photo for us

[rar110]

Does the compacted graphite iron block metallurgy conflict with the alloy radiator, and cause blockages?

[Graeme]

I'll pass on the suggestion. I suspect that my brother would also like to know just how badly it was blocked.

He doesn't have a high volume pump to reverse flush it but I have a 8HP 2" 600 L/min water transfer pump so if he removes the top tank but leaves the blockages intact then I'd like to reverse flush it to see if the blockages can be cleared.

[rar110]

I’m glad I have a spare radiator & intercooler.

Yes the results of a flush would be interesting. Ta.

[Eevo]

I'll pass on the suggestion. I suspect that my brother would also like to know just how badly it was blocked.

He doesn't have a high volume pump to reverse flush it but I have a 8HP 2" 600 L/min water transfer pump so if he removes the top tank but leaves the blockages intact then I'd like to reverse flush it to see if the blockages can be cleared.

i was more thinking cutt off the sides and have a look.

[Graeme]

The radiator has top to bottom flow and has plastic tanks so the crimps can be peeled back.

[Graeme]

Does the compacted graphite iron block metallurgy conflict with the alloy radiator, and cause blockages?
I expect not as LR has been using this combination at least since the introduction of the TDV6.

[Pedro_The_Swift]

is the top to bottom flow a lack of space thing?