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Discussion Starter #1
Hi, first post. 2months of ownership of a M139 sport GT 2007

So when I got the car I did just drive for bit without really checking anything. The car seemed mech A1. I noticed when stopping for a while at times where I have been going slow, the overflow for the radiator bubbles and gurgles. That to me sounds like boil over. The thing is, the temp guage never goes over 90degC. I've never seen it go higher and I've never got a overheat warning etc.

I decided to give it a bit of a look over. The coolant seemed low so I followed the manual, set the climate control to max hot to open the heaters and filled to correct level. Did a long drive and some slow driving before stopping. When stopping coolant overflowed all over the ground. Since then, the coolant level has obviously gone down. The tempt gauge still doesn't go above 90degC and it gurgles when driving slow and stopping like it is overheating.

Two theories here - 1. blown head gasket. Probably should get the coolant system sniffed for combustion gases. 2. bad thermostat. Should just replace it anyhow.

Anyone seen this? It's almost like the gauge is broken or they purposely didn't allow it to go over 90degC so as not to scare the driver (seen jeep do this with oil pressure because of complaints). That is jeep showed a fake oil pressure so drivers didn't get worried at idle! It's odd that it boils but temp gauge is not high.

thanks.
 

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90C is normal. Fill overflow tank to minimum when fully cold and try again. Head gasket would have white exhaust smoke (water vapor). Doesn’t sound likely.
 

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Mine (and most others that people have posted on) simply pick their own coolant level. As long as the temp is OK, you should be good I'd have thought

C
 

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Discussion Starter #4
Hey guys, thanks for the responses. Ok so there is definitely a problem. I'll need to keep sorting this.

I decided not to top up coolant and see what happens. Gauge stays 90degC, I stop and the coolant system is aggressively whistling out the overflow. Clearly overheating so I'd say the gauge is not telling the truth.

I'm still 90% this is a blown head gasket and a stuffed temp sender. Don't always get white smoke with a blown gasket. I can't see what else would cause this. If anyone has come across this, would love to hear it. No warnings from the car, gauge on 90degC, car overheating.

Thanks.
 

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Blown head gaskets are somewhat rare. Coolant sniff test?

C
 
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Generally what happens these days is that the heads will be warped...Most everything is using full out stainless steel head gaskets so they are hard to blow...You can use a fluid test to check for that or a gas analyzer if you have access to one...Jason
 
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Could it be a case where the cooling system simply isn't holding pressure, thereby allowing coolant to boil? In the old days when a radiator cap failed, you would boil coolant out the overflow tube, but not because of overheating, but because the system wasn't holding the correct pressure. Could the overflow tank cap be bad?
 

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Discussion Starter #9
Could it be a case where the cooling system simply isn't holding pressure, thereby allowing coolant to boil? In the old days when a radiator cap failed, you would boil coolant out the overflow tube, but not because of overheating, but because the system wasn't holding the correct pressure. Could the overflow tank cap be bad?
12 cylinders I like this idea. Yes quite possibly the lid is buggered.

If the F136 uses steel gaskets I agree that it's unlikely to be a blown headgasket.

I think I will do the following,

Test the sender and gauge by heating the sender in boiling water and see if I get the correct reading over 90degC on the gauge

Pressure test the lid

If all seems ok I will pressure test the entire coolant system.

I put more coolant in today and it sat on a nice 87degC while cruising home at 80klm/hr.
 

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perhaps you could look at the expansion tank. I have had 2 that developed cracks that did not leak coolant but would not hold pressure. Pressure is lower than water boiling point at sea level, so it’s difficult to detect.
 

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Discussion Starter #11
Well... It's definitely really hot tonight. Check my vid out below. I've another theory. Faulty temp sender is giving false gauge reading and false signal to ecu to turn on fan? Does the same sender do both?
I'll have to fix this before I go too far I think.

 
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I'm not really buying that theory....I would do a block test if the cooling system is building excessive pressure...Jason
 

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The gurgling sounds may indicate that there is still air in the system. Drive it and let it cool down, then re-add coolant as needed. Keep doing this until it stops gurgling, but don't overfill.
 

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Discussion Starter #15
So I've confirmed something today. Definitely gauge is not reporting true temp and fans not coming on. Running aircon puts a fan on and keeps temps much lower but not quite enough to stop a boil over. I'm 90% this is a dodgy sender causing fans to not come on
 

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You can get a thermometer to put into the reservoir. Use that and a obd scan tool (basic one is fine) to compare what the thermometer and the scan tool are showing for temperature. That’ll tell you right away if it’s a sensor issue or something else.


Sent from my iPhone using Tapatalk
 

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The sensor is a RTD. It changes resistance with temperature. Remove the connector and measure the resistance of the sensor on a cold engine. You can remove it put it in ice water and measure the resistance as it comes up to room temperature and then add it to hot water.
I have done this on another car that had cold start issue but at <-10C temperature. The sensor was still connected to the ECU but just in a container of water.
RTDs are pretty robust but it could be connection to ecu or a pocket of air at the sensor.
 

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Hi, first post. 2months of ownership of a M139 sport GT 2007

So when I got the car I did just drive for bit without really checking anything. The car seemed mech A1. I noticed when stopping for a while at times where I have been going slow, the overflow for the radiator bubbles and gurgles. That to me sounds like boil over. The thing is, the temp guage never goes over 90degC. I've never seen it go higher and I've never got a overheat warning etc.

I decided to give it a bit of a look over. The coolant seemed low so I followed the manual, set the climate control to max hot to open the heaters and filled to correct level. Did a long drive and some slow driving before stopping. When stopping coolant overflowed all over the ground. Since then, the coolant level has obviously gone down. The tempt gauge still doesn't go above 90degC and it gurgles when driving slow and stopping like it is overheating.

Two theories here - 1. blown head gasket. Probably should get the coolant system sniffed for combustion gases. 2. bad thermostat. Should just replace it anyhow.

Anyone seen this? It's almost like the gauge is broken or they purposely didn't allow it to go over 90degC so as not to scare the driver (seen jeep do this with oil pressure because of complaints). That is jeep showed a fake oil pressure so drivers didn't get worried at idle! It's odd that it boils but temp gauge is not high.

thanks.
 

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Hi, interesting reading... I have a 07 QP.( with later auto gearbox)
Hopefully it’s not a head gasket issue.. it might just be an air lock somewhere

Also, have you noticed if your radiator cooling fan comes on ?
I know mine does quite often...
Why not, drain the whole system and refill ..just to try.
Whatever... good luck with it.
 

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Discussion Starter #20
132460


This is where I start to cringe hard and almost cry. It would appear that my driving around with the system building up pressure has started to cause failures of seals in all sorts of places. I've got a radiator tank leak as well but this one..... It appears the O-ring between the castings has failed. Only way I can see to fix this is to remove the entire front cover from the motor (the one the thermostat housing is bolted to). Can anyone confirm? No easy way to solve this? I'm having terrible luck with this car. Thanks.

Oh, so my thermos definitely not coming on unless I run air-con. 99% the temp sender is bad. I've ordered a new temp sender. Will also get a new thermostat.
 
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