probably been asked before

[aussie4life]

I know this has been asked before. I'm guessing it's a common question but can't find the exact answer im looking for. So here goes

So one day a lil while ago, while driving to work, my VY exec over heated. Stopped. Let it call down. Drove to work. Grabbed the hose and filled the radiator up. When I took the cap off, it made a bubbling noise.

Drove to the shops tonight (have been given the work vehicle so not driving my car much) I've noticed coolant under the car where the reservoir bottle is. Got home. Car was up to temperature. Popped the bonnet. Felt the top hose. Scaldingly hot. Bottom hose was mildly warm but I sat there holding it for 30 seconds without getting burnt. Radiator cap was cool to touch. System had pressure in both hoses.

Enough of the back story. My question is, could a stuck thermostat cause the system to over pressurise causing the system to dump it's coolant into the overflow and then onto the ground when full?

Cheers in advance.

 

[Jxfwsf]

Thermostat is easy enough to test, pull it out, throw it in a pot of cool water and bring to the boil, if it opens it's ok.
Sounds more like a water pump (fins corroded off over time) or blocked radiator though.

 

[uniacidz]

Sounds like blocked radiator

 

[aussie4life]

Ok so time for a flush. But would that cause excessive pressure to build up and dump the coolant out the overflow?

 

[EYY]

A hot top hose and a cool(er) bottom hose is what you want. These systems run at above 100 deg C in normal conditions and so rely heavily on the a correctly functioning radiator cap. Definitely start by replacing the radiator cap and then go from there.

A bad thermostat (stuck closed) would generally make it run hotter, but I wouldn't think it would cause it to boil over.

 

[aussie4life]

Ok. Cheap stuff first. Gonna grab a new cap today and see how I go. Just thought it was strange that my cap was cold at WOT yesterday

 

[VSHeaven]

Your coolant overflow bottle could be cactus as well. There are a bunch of things that can go wrong with a cooling system. Radiator cap first, then thermostat. Both are cheap and easy to replace. After that it gets more expensive, heater tap, water pump and radiator. Sometimes the radiator hoses develop pinholes in them as well.

 

[mpower]

time for a coolant refresh imo - and changing a thermostat and hoses is a cheap and easy thing just grab a kit from Holden with a new housing.

 

[aussie4life]

well in the mean time ive grabbed a new radiator cap. fingers crossed that its fixed it. drove it around yesterday and checked the ground wherever i parked and nothing. res is still full so hopefully im just being paranoid. I know the pump and thermostat are working because when i refilled the radiator after taking the top hose off and flushing it out, it got up to temp as normal. Took off and pulled over at a mates place to have a yarn. when i turned it to on, it was half way between 1/4 and 1/2. as soon as i started the car, it dropped to 1/4.

 

[mpower]

Once you are happy drain that water out and do a fill with proper coolant.