Guys,

First ever mechanical problem on my 380, need help & advice.
Never had an issue with overheating, temp gauge has always read a bit under half (once up to operating temp) regardless of how it's driven or external temps.
Tonight, just as I got home from work and pulled into my garage, I heard the thermo fans going flat chat. I glanced at the temp gauge and it was off the scale, past the H mark.
I thought WTF!
I shut it down, let it settle for a couple of minutes, then restarted it. The temp gauge shot up to past the H mark in no time.
Only a couple of minutes before I pulled into my garage I changed by ventilation/air-con settings from combo defrost/feet (the setting before full defrost) with low fan speed and no aircon to the upper vent fresh air setting (all the way anti-clockwise but before auto).
In no time flat the front screen started to fog up so I set it back to where I had it before, but the fog got worse. I set it to full defrost, max fan, turned the temp right up, turned the aircon on and opened the driver's window, but it took a while to make any difference, when normally that combo of settings gives instant defrost.
So I thought the temp gauge going off the scale might have something to do with a malfunctioning heater/defroster/air con, and it might just be a false reading.
Fifteen minutes later I jumped back in the car to go down the shops, only about 1k away.
By the time I got half way to the shops the temp guage had again gone past the H mark, and same again on the way back after a 15 minute rest.
Funny thing is, every time I opened the bonnet (three times) the motor itself was quite cool.
Every time the top radiator hose was hot as buggery but the bottom radiator hose was cold.
I checked the radiator overflow bottle and the radiator itself and both are full.
No signs of any leaks or corrosion around the water pump.
So what's going on?
Have I got a blockage in the top of the radiator?
Have I got a blocked or stuffed thermostat?
Is the water pump stuffed?
Help!

Do both hoses have pressure after running it for a little while. Think you may find there's a blockage somewhere. Or it's running fine and the gauge is busted.

If there's no pressure, the water pump or thermo could be stuffed. If there is pressure in both top and bottom hoses it could be the gauge.

Do both hoses have pressure after running it for a little while. Think you may find there's a blockage somewhere. Or it's running fine and the gauge is busted.

If there's no pressure, the water pump or thermo could be stuffed. If there is pressure in both top and bottom hoses it could be the gauge.

Thanks Neo.

Just went for a quick run down the local bottle shop (ran out of beer, bigger disaster than an overheating car!), temp gauge started at about 1/8 and never went past the normal reading at about 7/16, either there or back. So, I thought to myself, bewdy, all OK, temporary thermostat malfunction, false alarm!

BUT, as soon as I stopped in the garage the thermo fans came on. I let it idle for a bit longer and the temp gauge started to climb again, towards the 3/4 mark before I shut it down.

Started it up again to check the hoses like you said.

The top hose was hot (but not effing hot like before) and the bottom hose was cold.

The top hose had a bit of pressure in it but the bottom hose had stuff all pressure.

So I'm thinking/hoping stuffed thermostat, shouldn't be too exxy to replace & can do it myself easy enough.

Hoping it's not the water pump though, had the timing belt replaced only 21,000 k ago and it's not such an easy DIY job.

Hmmm, that's very odd.

The hoses should be solid to touch after 5-10 minutes of driving. I would be leaning towards water pump as well due to the lack of pressure.

I assume you run coolant in your car? I ask this because I ended up with overheating problems in my last car, turns out the previous owner liked being a tightwad and used water in the system which in turn corroded the water pump and bearing, which gives the low pressure issues.

Be careful not to warp the heads :P

Do thermostat first mate have had a rum of them recently

Do thermostat first mate have had a rum of them recently

Thanks Mal.

I'm guessing I need a new one from a stealership, and I shouldn't waste my time looking at a second hand one from a wreckers, otherwise I'll just have the same problem again down the track?

Any idea what they go for?

Now the big question.

Can I still drive the car in peak hour stop start traffic for around 30 minutes without risk of serious damage to the motor or radiator?

I'm guessing not.

Just that it's a real hassle getting to work on public transport!

mine did the same thing a few months back changed the thermostat it had a crack in it's all good now part no MD3504150 and the List price is $34.02 l payed $29.25 easy to changed did it in 20 minutes l would drive it as you can do damage.

Thanks Mal.

I'm guessing I need a new one from a stealership, and I shouldn't waste my time looking at a second hand one from a wreckers, otherwise I'll just have the same problem again down the track?

Any idea what they go for?

Now the big question.

Can I still drive the car in peak hour stop start traffic for around 30 minutes without risk of serious damage to the motor or radiator?

I'm guessing not.

Just that it's a real hassle getting to work on public transport!

Fairly high chance of disaster if your car overheats to a shocking level and you are in lane 3 in peak hour. Bigger disaster if your hose bursts from being incredibly hot. Bigger disaster if your water pump blows and drenches your timing components in 150 degree coolant.

Not saying that all these things would happen, but what if? You can't rule it out.

"Can I still drive the car in peak hour stop start traffic for around 30 minutes without risk of serious damage to the motor or radiator?
I'm guessing not."
Spot on. I wouldn't drive a car with impeded coolant flow for more than 10 meters. You will have some bad thermal gradients, really hot cylinder heads and a cold block. Continuing to drive the car while you were busy wondering what was wrong may already have damaged a few things.

I'd rip the thermostat out and look at it. Dump it into boiling water on the wife's stove, and see if it opens. If not, you have found your problem.

If you really need to drive your car, do it without the thermostat. Or take public transport, the inconvenience of a bus is minimal compared to a destroyed motor.

Your choice in the end.

[Yes, I've seen what loss of coolant/closed thermostat does to the inside of an engine - not pretty, like a 5 mm gap between the block and the cylinder head because the head softened and the head bolts receded- scrap job for that engine, that was after a 13 km drive without coolant.]

HINT: If it is the thermostat and you replace it, keep an eye out for increased oil consumption and coolant leaks at the block/head joints. Overheated motors tend to do this at times.

I would probably buy a new thermostat when you do it. If you buy second-hand, you just don't know where it's been.

"Can I still drive the car in peak hour stop start traffic for around 30 minutes without risk of serious damage to the motor or radiator?
I'm guessing not."
Spot on. I wouldn't drive a car with impeded coolant flow for more than 10 meters. You will have some bad thermal gradients, really hot cylinder heads and a cold block. Continuing to drive the car while you were busy wondering what was wrong may already have damaged a few things.

I'd rip the thermostat out and look at it. Dump it into boiling water on the wife's stove, and see if it opens. If not, you have found your problem.

If you really need to drive your car, do it without the thermostat. Or take public transport, the inconvenience of a bus is minimal compared to a destroyed motor.

Your choice in the end.

[Yes, I've seen what loss of coolant/closed thermostat does to the inside of an engine - not pretty, like a 5 mm gap between the block and the cylinder head because the head softened and the head bolts receded- scrap job for that engine, that was after a 13 km drive without coolant.]

HINT: If it is the thermostat and you replace it, keep an eye out for increased oil consumption and coolant leaks at the block/head joints. Overheated motors tend to do this at times.

NEVER drive a third gen magna or 380 with no thermostat as there is a bypass function and with the thermostat missing the coolant will simply flow through the motor and sfa will find its way into the radiator, very bad advice here

Picking up a new thermostat from the local stealership in a few hours time, will chuck it in tomorrow (being Anzac Day), fingers crossed that will fix the problem.

And Max, yes I did catch a train to work today, first time in over 12 years. Relatively painless, and way better than risking an engine melt down.

NEVER drive a third gen magna or 380 with no thermostat as there is a bypass function and with the thermostat missing the coolant will simply flow through the motor and sfa will find its way into the radiator, very bad advice here

lol Only if you REALLY have to drive the car . . . . .Still better than the coolant not moving at all.

Picking up a new thermostat from the local stealership in a few hours time, will chuck it in tomorrow (being Anzac Day), fingers crossed that will fix the problem.

And Max, yes I did catch a train to work today, first time in over 12 years. Relatively painless, and way better than risking an engine melt down.

Slacker ,considering the train station is within a ten minute walk for you....think of the exercise.

All fixed!

Chucked the new thermostat in a while ago, let it idle for 20 minutes and the temp gauge never went past 7/16.

Stuck the old thermostat in a pot of water and bought the water to the boil, and it never opened. Obviously cactus.

Both the old and new thermostats (which by the way are not quite identical) have "88 c" stamped on them, so I presume they are meant to open at a water temperature of 88 degrees centigrade.

Not quite a 20 minute job, more like an hour, but nowhere near as complicated as the service manual would have us believe.

Thanks to Neo, Mal and Magnador for your advice.

lol Only if you REALLY have to drive the car . . . . .Still better than the coolant not moving at all.

Wrong yet again.......If you need to move the car to move it off the road etc you will not remove the thermostat, you will make sure the motor is cool and just start it. If you are going to remove the thermostat to just move the car you are an idiot as a closed thermostat will do just as bad as none at all. If you are stuck in the middle of nowhere get one posted as even if you drill holes in the thermostat like in the old days, the bypass plate still will be open and the coolant will flow through the path of least resistance

Treaddyman, glad was fixed easily mate, as I said have had a run of these in 380's of late for some strange reason, had a few J.L and W series magna's as well for same thing, Mits may have changed the manufacturer of the unit at some stage perhaps as E.F and H series dont seem to have been much of an issue despite being older

My 380 had the exact same problem. Although the idiots at the mechanic thought it was the Radiator and replaced it without telling me, meanwhile I was thinking thermostat the whole time. Drove off from mechanic and same problem. Went back next day and what do you know it was the thermostat. Paid for a radiator when I only needed a thermostat...

I would have refused to pay for the radiator

Just found this. Would it be better in the 380 thread?

If you are going to remove the thermostat to just move the car you are an idiot as a closed thermostat will do just as bad as none at all.

Agreed. Any engine with a bypass coolant circuit behaves the same with a stuck-closed thermostat as with no thermostat. The bypass circuit is basically a loop that allows coolant to flow out of the motor and *immediately* back into it without going through the radiator. When the engine heats up with this system, the thermostat does two jobs. One, it opens the flow path to the radiator and TWO, it *closes* the bypass circuit. If you remove the thermostat the coolant will take the path of least resistance, which is the bypass circuit - immediately back into the engine rather than through the radiator.

The coolant don't care how hot it gets, it will just keep on looping through the motor getting hotter and hotter until the motor fails.

In summary, as Mal said, do NOT run ANY engine that uses a coolant bypass circuit without a thermostat. Ever. Not to the shops, not to the servo to get some cigs. Just don't do it.

NEVER drive a third gen magna or 380 with no thermostat as there is a bypass function and with the thermostat missing the coolant will simply flow through the motor and sfa will find its way into the radiator, very bad advice here

Tell me more about this bypass. I'm not running a thermostat in my 3rd Gen.

Tell me more about this bypass. I'm not running a thermostat in my 3rd Gen.

Indeed? Was it just removed or was the bypass circuit also blocked off? Nothing "wrong" with running no thermostat if you close the bypass circuit (aside from the fact the motor takes longer to warm up and may run too cold when on the freeway). I've heard of guys gutting thermostats before so that the main circuit is always open but the bypass plate part is still there on the end of it. Most engine EFI systems will richen the mixture up if the engine temperature is cold. It can cause excessive fuel consumption in cold weather but if your car is turbocharged it probably loves the rich mixture anyway.

Update: Actually, looking at the service manual now, the bypass circuit looks like it's part of the thermostat housing assembly. The engineers who built your engine might have completely replaced that with something that doesn't have a bypass circuit in it or even space for a thermostat. Essentially, it could be like a port job except for the cooling system - nice and straight with no sharp turns! I did a bit of reading on your car and since it's so heavily modified you're probably running a full Haltech ECU in it which has been tuned specifically in the knowledge there is no thermostat, so there would be no issues with it ever running too rich when on the highway on a cold day.

Tell me more about this bypass. I'm not running a thermostat in my 3rd Gen.

How is your heater on these cold days?

Bro in CBR had a faulty thermostat ( always full open) in his Audi A6 ( I know wash my mouth out with soap) and froze his "A" off in the cold down there. Used cardboard across radiator to get engine to reasonable temp till he could get a new thermostat installed.

Major job on that engine as it is buried internally as part of pump behind timing belts etc etc

How is your heater on these cold days?



Dont need a heater in my car. The amount of heat the comes off the engine and exhaust after the turbo is enough to have to open the sunroof in winter and the temp is perfect.:)