Car engine overheating

After radiator replacement in my Honda Oddyssey on any longer trip I need to run heater full on to avoid water boiling in the radiator.
That add extra strain on my recent 400km trip to Burrum Heads in 30+ C temperatures.
Brand new radiator was fitted.
To mitigate the problem I replaced thermostat, without any significant improvements.
I ordered full inspection and service, still no lucky.

If there is anything I could do ?
Obviously using air con is out of question - even 10 minutes trip will boil the water.
Both fans on radiators works. Maybe bigger fans on radiators ?

One clue to the problem could be use of leak preventing (colloidal copper ? ) liquid on old radiator just before replacement. Obviously common mistake that doesn't help at all since crack was in plastic radiator parts. Maybe that stuff clogged something in the engine or water pump ?

IM no mechanic but have a mechanical workshop next door and i see many radiator issues. Did you do the job yourself? Could it be the wrong coolant ? Or possibly be the new radiator? The guys have had so many problems with radiators they now have a deal that when installing a new one, if their is an issue the radiator supplier will pay for their time to refit.

Make sure the radiator system is completely sealed. Most modern engines run coolant temps very close to boiling and if the system wont hold pressure then it will boil as a matter of course.

Is the radiator actually boiling,. or is it just frothing and bubbling? (yes I know,... hard to tell.)
If it is actually boiling then it should stay boiling for at least 30 seconds or more after you stop the engine.
Does it continue boiling after you stop the engine or does the boiling stop immediately after you stop the engine?
If it stops immediately after you stop the engine, it's not boiling, it's bubbling with exhaust gasses.

It could be that there is a leaking head gasket or cracked head which is leaking combustion gasses into the water jacket.
This looks a lot like boiling because the radiators in modern cars normally run close to boiling point anyway so it's hard to tell the difference.

You can usually tell the difference if you smell the radiator fluid. If it smells at all like exhaust gasses rather than just water, then the problem is gas leakage rather than water boiling.

If the problem is really bad you can check this by taking off the radiator cap on a COLD MOTOR, starting the motor and then rev it up and down a few times very hard, like full throttle on and off a few times. There should be no bubbling. If there is then there is gas leakage into the water jacket.

Minor gas leaks can be fixed with chemiweld or similar product, added to the coolant.

SAMEH may be on the money. So when car engine is cold - check the oil filler cap - if there is a milky residue = water oil mix = head gasket.
Last time I blew a H/Gasket (outback SA) the bush mechanics tip - don't do the radiator cap up completely - so pressure in the system from the gasket leak could vent w/out blowing water out at the same time - worked a treat - that was a major relief as the inside of my car was full of anything to hold water for the 10 minute stop and top up cycle - eyes peeled for the next water source. This was some time back and most all cars have an overflow / reservoir - same applies here re-cap.

Also check oil system it needs to circulate to help heat transfer.
In your shoes - try removing thermostat take radiator cap off and see how good the circulation is - sluggish = blockage - most likely point = radiator - still!!
The only reason for the thermostat is to help car warm up faster - so removing it is not a major issue.
Chuck your thermostat in saucepan of water and heat - watch how much it opens.
You could get a big enough bucket and include it in the circuit - sucking into the engine from bucket and emptying from radiator into bucket - if you think the radiator is blocked - reverse the pipes to fill the other way round - still into the bucket... But realistically this is what the radiator place is meant to do.

What else -
- Well head gasket may be damaged and blocking some of the flow.
- A/C radiator may have been damaged to the point it is blocking airflow back to the engine radiator.
- Have you recently mounted some kit on the front of the Honda Odyssey which limits the airflow?
- Knowing your previous posts - you should be able to hot wire the radiator fans to bye-pass the temp sender - so always on - if this works - you have bought time till it gets fixed

Let us know what works
Good luck

Regards
AP

Run it on solar-power. Doesn't matter how hot it gets then.

Are these cars that have had overheating problems or cars that function okay? Removing the thermostat can make the heat exchange worse... so they say.

Removing the thermostat is a major no no.

Most engine wear occurs "as" the engine reaches optimal temperature. An engine will last 10 x's longer if it always ran at it's perfect temperature (but we know this is near impossible to achieve). That's why you should warm up your engine before you nail it down the road and preferably wait till it's at normal running temp before you bounce off that redline.

If you do remove the thermostat the engine will not last very long. Just remove the old thermostat from the engine and boil some water and drop it in. If it opens to it's maximum flow its fine.

Edit: Sorry harrow I think your mile's from the point. Not sure what your working with - maybe HVAC? but certainly not piston engines. Performance is improved by cooler inlet temp's not running temps. A 2 stroke will have a slight performance increase due variation in size due to thermal contraction but is very minimal if at all noticeable. 4 strokes thermal contraction or expansion is not not noticable at all due to size.

In the Toyota surf topic it is more noticeable as its a diesel and the way the water jackets are placed around the block and head. Once again though removing a thermostat from a diesel will just decrease fuel efficiency and power or lack of.