weird cooling problem

[Sprint]

not a landrover question, but anyway....

recently gave the cooling system on the falcon a birthday, replaced all the hoses, thermostat and changed the radiator for one i had spare after i found a few dried coolant tracks on the core ends

now, running at 110, the temp normally sits halfway on the gauge all the time, but since the changes, the gauge reads a couple of degrees cooler untill i've been driving for 20 minutes, rising to the 3/4 mark unless i turn the heater on.....

the radiator i dropped in is an adrad rebuild of unknown vintage with about a dozen of the tubes crimped and soldered off, which would explain the higher temperatures, but whats got me stumped is:

1: why the sudden rise afer 20 minutes
2: as soon as i drop down from highway speeds getting into town, the temp will drop approx 10 degrees in 2-3 minutes.....

[Blknight.aus]

your making more heat than the existing radiator can deal with and you may also have a dodgy thermostat.

[Sprint]

i figured out the underachieving radiator thing, but its just wierd how it does it pretty much on cue, temp goes up give or take a couple of k's, and how the temp goes down as soon as i get into town and drop down from highway speeds.....

[forget]

radiator probably need a good fush,rip it out and take it to the rad shop and have them rod it for you maybe.

[Blknight.aus]

not really, its repeatable so thats good

it takes X amount of heat for y time to generate enough heat to warm everything up to the point where the radiator looses the battle.

if you ease up on the power levels (ie slow down) you make less heat so the radiator has a chance to offload what it couldnt before if you turn on the heater you're pulling extra heat out of the system.

give it the beans and it'll warm up faster

[Sprint]

just concerns me a little that more or less in the time it takes me to coast down to 60 from 110, it'll drop ~5deg......

should add that i've got a new 3 core rad here waiting to go in on sat afternoon (once its cooled down from coming home from work lol) im just concerned there might be a problem that would be masked by fitting the new radiator.....

[mike 90 RR]

..... Just install the new radiator .....

[Sprint]

..... Just install the new radiator .....

which, if there are pre-existing parts, will simply mask the problem untill something fails.....

[Blknight.aus]

so do all the normal checks

pressure test it cold
pressure test it hot
check the flow rate
check the thermostat opening temperature
check it for bubbles

if you only changed one component and the performance changed...........

[Sprint]

pressure test it cold - havent tried it
pressure test it hot - passed
check the flow rate - how?
check the thermostat opening temperature - going by the gauge, the thermostat opens around the same temp as the original one used to
check it for bubbles - none apparent - did a exhaust gas test too - checked out fine

if you only changed one component and the performance changed...........

changed radiator and thermostat..... might get up early and chuck the new radiator in it before work tomorrow.....

[Sprint]

wierd development tho, opened both front windows when i drove home this arvo, left the heater on as per normal, and you think it wanted to get hotter than it should?? not on your bloody life!

[alien]

Does this mean the heater wasn't heating up due to a air in core(needed to be bleed)?

Or
The old trick of turn heater on to aid coolong the system on steep hills trick confermed radiator is blocked.

Sounds like the spare radiator fitted is not healthy.

Cheers.

[Sprint]

radiator works great, but i had to leave it on just to help keep everything else to a sensible temp