Bubbles in radiator straight after startup

[AusM4500dt]

Hi all,

I have an m4500DT. Bought second hand and the old owner told me it "runs hot".

Sure enough, after 30 minutes or so of slashing, it is up to the high end of the temp gauge. I've only run it like that twice.

We changed all the coolant and it was very rusty, but mo obvious signs of oil in there. A lot of flushing later and it was staying much clearer.

We changed the engine oil, no sign of coolant in that.

I checked today and there are small bubbles coming through the top of the radiator pretty consistently, but they started straight away when I started it up, way before it would have gotten to operating temp and had the thermostat open.

I had it suggested that it may have something to do with a blocked radiator core and cavitation at the water pump (i sort of know what cavitation is but now how a blocked radiator would cause it), rather than a head gasket, and to start by getting the radiator professionally cleaned, or replacing, then doing some more flushes with the thermostat out and an in line rust filter on the return hose. Then replacing the thermostat.

I'm not sure if it's also worth getting a combustion gas test kit to confirm. I couldn't smell exhaust from the radiator opening as the bubbles came, but my nose isn't that good sometimes.

I'd love to hear any thoughts about what could be going on, and any advice on how to approach it.

Many thanks!

Simon

 

[Hugo Habicht]

Hi Simon,

get a CO2 test kit, they are cheap, just to confirm it's not the head gasket. The bubbles could be sucked in at the gasket at the water pump, seen that before.

If your radiator flushing fixed the overheating and the CO2 test is negative I think you are fine.

Kind regards,

 

[AusM4500dt]

Thanks Hugo, will test for gases and see.

Flushing the radiator definitely hasn't stopped it getting hot quickly though.

Cheers,

Simon

 

[Russell King]

I agree with @Hugo Habicht that it is probably the head gasket that is leaking combustion gases into the radiator.

You will probably need to replace the head gasket and oil seal orings between the head and block. You should also have the head checked for cracks and warping by a machine shop that deals with engine heads regularly.

If it has been run hot for too long the head may have to be replaced. Post pictures of the head to block surface to have some expert advice on potential cracks if you have to remove it.

 

[Tughill Tom]

Pressure test will tell, most likely head gasket and get the head checked for warping and or cracks.