Overheating (Not the usual culprits though?)

[RensoreK]

Good day everyone. I have a P5 with an overheating issue. The coolant boils over in the overflow tank when I put a load or go up steeper areas. When just idling I notice bubbles slowly creeping up. Someone had suggested to purge the system using the heater which I did and it still has been going on for a while now...

I have checked:

Thermostat (OK)
Hoses (OK / no leaks no swells)
Radiator (OK) (Only has about 5 months and less than a week ago had it checked at a Rad shop, everything came out ok)
Pump (OK/Replaced)


Tried coolant ratio @ 50/50 and then 70/30. Boils less but still does. I don't have usual symptoms of a damaged head gasket though. No moisture in exhaust, no mixing of oils or coolants. When the heater is on I dont get a coolant or odd smell coming out that usually indicated more of a problem. Spark plugs seem OK and Oil cap doesnt show a mix of fluids. I don't have a wheezing/hissing noise when usually the head gaskets are bad.

Can someone point me in the right direction??

 

[pcb]

Are your fans coming on ??? Does your temp gauge rise ???

You could still have a bad head gasket,... compression pressure could leak into the coolant without any of the symptoms you mentioned. There is a lot more compression pressure than oil or coolant pressure and you could have a small one way leak. A leakdown test can help diagnose it. (a compression test isn't good enough)

 

[pcb]

I just remembered,... you can get your bubbles tested with an exhaust gas sniffer to see if the bubbles have exhaust in them. A properly equipped shop will be able to do it.

 

[RensoreK]

Are your fans coming on ??? Does your temp gauge rise ???

You could still have a bad head gasket,... compression pressure could leak into the coolant without any of the symptoms you mentioned. There is a lot more compression pressure than oil or coolant pressure and you could have a small one way leak. A leakdown test can help diagnose it. (a compression test isn't good enough)

I forgot to mention fans lol. But yes Torque shows 97C and thats when I noticed the fans kicked in. Drops to about 86C. This is all at highway travel. Idle it overheats but I guess the fans are able to bring it down to a manageable level.

 

[pcb]

You could have a hairline crack in the head that opens up just enough to cause a leak when it's warm. Or something similar with the head gasket.

I think getting your bubbles tested would be your best plan.

 

[Luken10]

AutoZone has a block tester you can rent for free with a deposit.

I had really similar problems. The coolant tank would be boiling and bubbling like a halloween cauldron after spirited driving. I also noticed bubbles coming from my coolant overflow tank. Except my car never registered as overheating, via torque or the gauge.

For me it was just the radiator cap, huge relief! I am assuming the system was not under pressure, making the boiling point much lower. Haven't had a problem since, and no more bubbles. Block test also came back negative.

You said the radiator was checked, so maybe it is something worse. Definitely doesn't hurt to give the cap a glance again. Best of luck!

 

[hornsfan10609]

I would do a compression test, bubbling in the coolant while idling is a sign of a bad head gasket. My MSP did the exact same thing when the HG blew, at idle the overflow would bubble slightly and when you rev it you could watch as more bubbles would show.