Foamy coolant

[Parksy]

Hi all

Have been doing some testing on my tb42e motor to see if it has any hidden problems such as head gaskit issues. I cut a 2l coke bottle in half and tapped the neck end onto the filler cap of the radiator and filled it with water to see any visible bubbles. While there aren't any bubbles, the coolant does get abit foamy on the surface. It also appears that the thermostat had been removed or is stuck open. Is this foamy coolant cause for alarm? No doubt it has had mixed coolant added to it, so maybe a flush and some fresh coolant will stop the foaming?
Thoughts and theories are more than welcome.

Cheers

Andy

[threedogs]

Dump that coolant and start again, mixing coolant MAY cause the coolants to turn to gel and Block your radiator.
I'm a big fan of the coke bottle trick, Park somewhere nose up when you re do the coolant use an OE thermostat
Cavitation is probable cause of your bubbles, thats m2cw

[Parksy]

Thanks threedogs. Will be flushing the system soon and fitting a new radiator. Seems the old one has a leak somewhere and I'm not going to bother fixing it so a new one will do just fine. Also have an oe thermostat on its way. Will hopefully fix my cold start drive ability.

[Parksy]

Hi all.
Flushed the system, installed a new radiator and found the old one quite blocked up which I'm assuming is why the thermostat has been removed. Installed a genuine nissan thermostat and tried the coke bottle test again and no more foaming coolant. I'm guessing the lack of thermostat was creating too much turbulent flow hence the foaming. But I'm happy with the result. Also happy to find underneath the actual thermostat, which is the head part of the thermostat housing isn't dirty at all. Either the previous owner has taken good care of the cooling system or this has had a new head installed at some point which is only good news.

Anyone know anything about part number locations on the blocks and the heads? Curious if there's a way to identify if the head has been changed. Any ideas?