I took the Ralliart out today for a run. I don't use it as a daily driver and it is in pristine condition with only 98000km. 41 degrees today and the chosen route has an approximately 5km steep, winding climb with a couple of 25km/hr hairpin bends. The first part of the drive was on undulating country road and I did notice the temp gauge climb about half a segment above the usual position (about half way on the guage like most third gens) on a couple of hills.

I get about half way up the climb and the temp climbs quickly to 3/4. Only problem there is NOWHERE to pull over for about 500 metres due to guard rails right on the shoulder. By the time I can stop the gauge is reading just above the second last white line. The coolant overflow was taking in coolant and bubbles before overflowing a couple of hundred ml.

I let it cool down before returning home. No troubles with the temp but all downhill home. Took the thermostat out and it is stuck closed.

Goes to show that they can fail at less than 100000km. My advice - replace them at every timing belt change. Hopefully I haven't cooked the heads.

Any thoughts about what this would correlate with temperature wise - second last white line on the gauge?

Once the thermostat decides to stick closed (or open) the effect on the temp gauge is pretty rapid for a stuck shut one, bit more subtle if stuck open.
Hopefully hasn't softened or otherwise damaged the heads. Now if you hadn't noticed . . . .

"The coolant overflow was taking in coolant and bubbles before overflowing a couple of hundred ml."

And Bubbles! I immediately think the worst - you may have a blown head gasket. I had one blow on my old Range Rover. Compression tests told me nothing - all normal, but once the temp got above a certain level, I could feel it lose power. It also made water in the overflow bottle. I had to choose which head to take off and check. I chose the most awkward because if it wasn't the offending one, the next one was easier. I found it tracking betwen into the water jacket. Minimal shave of the head and put it back - all good.

It ran fine on the way home. No evidence of oil or coolant contamination in respective fluids. It was only hot for probably 60 seconds so fingers crossed. I understand the third gen engines are a bit tougher than the 2nd gens?

I think the coolant was simply boiling as it escaped the first radiator cap seal and flowed into the overflow tank. Naturally at normal atmospheric pressure, the coolant boils. This is what I hope......

I would expect that you have not done any damage. Suggest that you replace the thermostat first. Then check that the fans are working when it gets warm and calls for them. I only suggested the head gaskets as a last resort. Hopefully it hasn't gone that far. If it is the gasket, which one???

The overflow only started when I turned off the engine thus I think it was just boiling coolant. The thermostat is definitely stuck closed. I did the throw the thermostat in boiling water test and it didn't budge. I've ordered a genuine thermostat and radiator cap. Thought may as well replace the cap at the same time. Thermo fans turn on and off correctly.

Thermostat $40, cap $40 too!

Steve

I was born a pessimist and I immediatley think of the worst possible thing that can go wrong. Hopefully a new thermostat will cure all. I think it will.

I have fitted an Engine Watchdog to my vehicles. This is a thermocouple which bolts onto the engine in a suitable place and monitors the engine temperature. WHen it exceeds a pre-determined value, it sets off a squealing noise which is impossible to ignore. At least you don't have to keep looking at your temperature gauge all the time. My wife was a passenger ina TM Magna which blew a welsh plug. SHe saw the water briefly come out of the L side of the bonnet. She said to her friend "You are losing water" The driver looked at the temp gauge and as she said it was OK, it went up and immediately went back to low. It was that quick. I certainly don't watch the gauge as often as I should. I know that my wofe rarely looks at the gauge, so it is a valuable protection.

I have looked at these on and off over the years and thought "no". I now might look into getting one. I could fit a 380 engine to the Ralliart if needed but I want to keep it original. A rebuild would not be cheap.

I asked my wife to get the parts as I am in a job where I can't go out during business hours. She asked for a thermostat for a "Ralliart". Evidently the guy looked puzzled and asked what type. He had never heard of a Magna Ralliart and this is at Holden/Mitsubishi spare parts.

Steve

I asked my wife to get the parts as I am in a job where I can't go out during business hours. She asked for a thermostat for a "Ralliart". Evidently the guy looked puzzled and asked what type. He had never heard of a Magna Ralliart and this is at Holden/Mitsubishi spare parts.

Somewhere I gained the impression that the Ralliart engines were fitted with thermostats much "colder" than the thermostats in standard Magna engines. I would suggest using your VIN to determine whether the actual Ralliart part is the same price, as I expected it to be considerably more than you quoted earlier :(

I gave the VIN to my wife to show the parts guy. Apparently he looked it up on the computer. Fingers crossed. The one I removed is stamped either 88 or 89 degrees.

Well, new thermostat is in, system flushed and new Nulon long life coolant 1:2 with distilled water, all air bled from system. Took 30 minutes total. Went for a "spirited drive" at highway speeds, running engine up to 4500rpm up hills. Only 29 degrees ambient but temp gauge seems nice and stable in the middle. However, went for a drive up to the local lookout - about 1km of sharp bends on a steepish climb. Temp went up about one segment. Both fans running at the top.

Not sure what to make of this.

No bubbles at all going into overflow tank, no evidence of oil or water contamination respectively.

I've never had a coolant leak and radiator is in excellent condition.

Wonder what would happen on a 40 degree day?

Steve

Well 34 degrees and went for a drive. Same steep lookout drive. Went just above half (from just below the mark at half way) so increased about half an increment.

Hopefully this is Ok

Just before Christmas I drove through 46C temps, with the airconditioner flat out. The only time it went to one notch above half way was when the wind was coming from the side, where it doesn't push you along and it reduces the effectiveness of the radiator fans due to a slight vacuum effect (hope that makes sense), coupled with some small hills.

On a side note, and this technically would help cooling, I strongly recommend insulating the air conditioner pipes for their full length. Like with most cars, there is a lot of bare metal there to heat up and reduce air conditioner effectiveness. Having travelled through the 46C temperature I can say it does make a difference! The pipe the insulate is the return pipe from the front, it is the wide diameter pipe. Some sections are hard to get to, but like I said, well worth it!

Remember that the temperature gauge is not linear. If you consider the gauge rane from 0 to 10 (0 being cold and 10 being the red mark on the gauge), mid range is about 85 Deg C and the 10 is about 110 Deg C. FOr the needle to creep by about a needle width, it isn't much of an increase. Now, I am not saying "IGnore the gauge", but don't be too upset by a slight increase under arduous conditions. Having said that, I have only seen the needle move less than half a needle width under the most extreme conditions - idling in a traffic jam with the outside temps over 40 Deg C.

The thermostat in our Magna takes forever (up to 4 km) to get to operating temperature whereas my Pajero gets there in about 1 km. The Pajero gets up 1 needle width climbing a long (15 km) hill in 2nd or 3rd gear whilst towing our caravan. I have an engine watchdog fitted and the digital readout then climbs from an indicated 83Deg C to up to 90. In traffic jams at idle, it climbs to 95, but as soon as you start to move, it goes back to 83 or so. I have the thermocouple mounted on an inlet manifold bolt so that hopefully I can detect the head overheating, not just the water. They recommend attaching it to the thermostat housing, but since the housing is so far away from the heads in a Mits, I opted for the direct attachment to the head (or as close as I could get). What it does tell me is that things are generally OK inside the engine compartment, but more importantly it screams at me if the temp goes over 95 Deg C.

Well I thought I'd just double check as much as I can at home, following the service manual. Fans come on at the various speeds by supplying 12 v as per the manual. Checked relays - all switching correctly but there is no mid-speed relay present in my car! Is this normal? The manual says the 3.5 l engine has 3 fans speeds so I assume the relay has been flogged for some reason - maybe to replace a faulty relay elsewhere.

I swapped the horn relay over for a test and will go for a drive later. If the ECU is calling for mid-speed on low speed climbs then this would explain why the temp rises a bit.

Any comments?

Steve

And I am going to get a watchdog or similar......

Just took car up same lookout in 37 degree heat. Gauge went to within 2 segments from the red. Can also replicate it at stand still running the engine at about 3000rpm.

Something is wrong.

Radiator?
Water pump?
Head gasket?

Just took car up same lookout in 37 degree heat. Gauge went to within 2 segments from the red. Can also replicate it at stand still running the engine at about 3000rpm.

Something is wrong.

Radiator?
Water pump?
Head gasket?

Dads kj was doing this. WE replaced thermostat to no luck.

Ended up buying a new radiator off ebay and that solved it. He needs his car for work so wasnt easy to get a flush. Easier to just replace. His also would cool down if you put the aircon on. Im guessing it would trigger both thermo's

I guess there could be partial blockage in the radiator. I am led to believe water pumps rarely fail at low kms on these cars (mine has 98000km). Can't see any obvious evidence of a head gasket issue. I guess a small defect might cause some overheating without obvious other symptoms.

Most likely is the radiator. Fairly easy to check too, although to really do the jopb requires that the header tanks be removed and the core cleaned out with rods. Check the airflow through the core. If there is some blockage in the middle of the core (or fin damage), this will restrict airflow and then cause overheating. When water pumps fail, they normally leak water everywhere.

As a last resort, go back to the head gasket and my earlier post. My Range Rover only started to blow when it got over a certain temperature, and there was a noticeable loss of power at that time as well. I could at least do a compression test in each cylinder but by the time I got to do it, the thing had coold downn and was sealing again, so no differences in readings. Evenyually I took the plunge because there wasn't anything else to check, and I found a very small tracking through the gasket. Minor shave of the head and all was well again. Hope it isn't a head gasket.

I think I'll look at the radiator next, as suggested.

As a last resort, go back to the head gasket and my earlier post. My Range Rover only started to blow when it got over a certain temperature, and there was a noticeable loss of power at that time as well. I could at least do a compression test in each cylinder but by the time I got to do it, the thing had coold downn and was sealing again, so no differences in readings. Evenyually I took the plunge because there wasn't anything else to check, and I found a very small tracking through the gasket. Minor shave of the head and all was well again. Hope it isn't a head gasket.

3rd gen V6's have a metal head gasket.. very rare for them to go, usually only fail under extreme conditions (bad overheat causing warped heads)
The OP has said there are no usual signs indicating this condition (the bubbling sounds would have been just boiling coolant after the car was turned off).

How old is the radiator cap? If it isn't holding pressure correctly sometimes I got the bubbling sound into the overflow.
Definitely sounds like a radiator issue now. If it was me I'd try a new cap first (if the existing is old), failing that, a new radiator to go with it.

I purchased a new genuine cap with the new thermostat. As above, that certainly leaves the radiator as the most likely remaining culprit. I'm probably just going to replace it rather than muck around with it.

The original Denso radiator is out. Looks pretty good. Fins clear, water flows through readily although being no expert I doubt this can exclude a partial blockage somewhere. Ordered a new one anyway. Will put it in next week.

Interestingly, the general consensus on the poll you issued was that you don't need to worry about replacing thermostat as a preventative measure (http://www.aussiemagna.com/forums/showthread.php?t=98901&page=2)

Yet in your case when it did fail you potentially would have been forced to drive further, uphill, before being able to stop...

I tend to agree and suggest changing the thermostat at regular intervals - perhaps 50,000kms? The cost really is quite low and easy to change as part of a service (or on its own depending your service schedule habits)

Is it possible you have air in the system causing the intermittent heat issue?

Did the old thermostat actually fail? Since the problem is still there with new one, his old thermostat may have been fine. Seems a waste of time to replace something that, in my experience, works for well over 200,000kms.

Did the old thermostat actually fail? Since the problem is still there with new one, his old thermostat may have been fine. Seems a waste of time to replace something that, in my experience, works for well over 200,000kms.

Waste of 5 mins perhaps. At least you have the peace of mind knowing that it won't fail.

The old thermostat was definitely stuck closed. Was calcified and a bit rusty. Also Didn't open at all in boiling water. I think there are two issues. Just need to chase the second one down. Thing is radiator and thermostat replacement is cheap in the scheme of things and I get to learn in the process. The previous owner left the cooling system maintainance out of his schedule I think

I will replace the radiator when it arrives and give the system a good flush. Have previously drained the block so will do the same again. Not too hard on car stands.


If this fails to fix the problem my mechanic will have some work. Carbon monoxide leak test and get the water pump looked at.

I completely agree that it was a good idea to change it in your situation. Best of luck with the new radiator, hope it fixes the problem.

If its not the radiator then perhaps its time for a compression test or a new water pump. All the best to you.

An update.

New radiator arrived this morning. Thought I'd try one of the Fenix aluminium core radiators as there is some good feedback on the web. Also purchased an Engine Watchdog as recommended by Erad - thanks!

I went for a run, trying the same steep lookout hill as before, ambient temps 32 (a little cooler than last time).

Guage did not move over two runs. Engine Watchdog read temps of 86 at the bottom of the hill, peaking at 92 max. Interesting that thermo fan not on at that temp. I got home and ran the car in the driveway at 3000rpm, temps on the Watchdog peaked at 105, guage went to exactly half, thermo fans on. HOWEVER, I have the thermocouple washer on one of the timing cover bolts. This goes into the front head but it is very close to the exhaust. I think this was falsely elevating the Watchdog temp whilst stationary. Previously the guage crept towards red in the same situation.

Problem fixed (I think).

Steve

And talking about how non-linear the guage is. It goes to the usual just under half position at about 60 degrees on the digital readout and stays there into the 90s.

Tested the car on a 40km drive, mostly highway speeds with two steep climbs. Mild outside (mid 20s). Engine temp sat on 74-78 degrees. Arrived home, sure enough bottom radiator hose only warm so thermostat still closed.

Great little gadget the Engine Watchdog. Highly recommended with some of peace of mind knowing you will detect overheating very quickly.

Fenix radiator also seems very well built. Fitted perfectly.

Is the washer on the watchdog big enough to fit under one of the thermostat bolts? If you put it there and cover it with tape to reduce the cooling effect of air flow, you would get a more accurate indication of the actual coolant temperature. At the moment you are reading cylinder head temp.

Yes the washer is big enough to fit under a thermostat housing bolt. I was more keen to read the actual head temp rather than the coolant temp, although they do seem to be similar anyway. Thermostat starts to open with the Watchdog reading 86-87 degrees at its current location. It is an 88 degree thermostat.

Good thing about the design is you can move it around if it want.

Well I finally went on the same drive that caused the overheating. Not as hot but temp on Watchdog peaked 87 degrees - thermostat just started to open on climb but the new radiator kept the temp in check. All fixed. Just goes to show that a radiator that seems to flow well when flushing can still be blocked up. A thermostat that opens properly obviously helps too!