Guys,
How can I definitive,y tell if my radiator has some blocked tubes in it? If I flush it out it seems to run ok, but I am having some overheating issues that I can't nail. Already replace thermostat, hoses, water pump and themo fan but still have issues so I am thinking it must be the radiator itself.

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Model would help

i believe he has a tm
have you removed the radiator and flushed water throw the bottom hose whilst it upside down .
all get a radiator joint to check it for you

Yes it is a TM. I have had the radiator out and flushed it upside down when I first started having overheating troubles. Should have mentioned also that I have replaced the radiator cap. Having replaced just about everything else all I can think of is that there is something blocked in the radiator, though when you look at it from the filler hole it all looks to be in good nick. That's why I was hoping there was some magic way of telling if it was blocked.How do the radiator guys tell?

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If you have reverse flushed it, it won't be blocked.
What exactly leads you to think the radiator is blocked?
Other things, like a blown head gasket, corroded water pump vanes, etc can give overheating symptoms as well.

Max,
It's just from a process of elimination that makes me suspect there is something wrong with the radiator. I have already replaced the thermostat,pump,top and bottom hoses and radiator cap. Head gasket was done a couple of years ago and I don't have any other symptoms of a blown gasket. Sometimes I can drive slowly for 5 minutes and it will start to get hot, other times I can go for hours with no problem. Doesn't seem to be related to when the aircon is on or even to the outside temp as it can do it at 6am. But with summer coming on I don't want to end up stuck somewhere.

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Is the thermo fan actually kicking in? It may not be working at its highest speed causing a lack of airflow.

Max,
It's just from a process of elimination that makes me suspect there is something wrong with the radiator. I have already replaced the thermostat,pump,top and bottom hoses and radiator cap. Head gasket was done a couple of years ago and I don't have any other symptoms of a blown gasket. Sometimes I can drive slowly for 5 minutes and it will start to get hot, other times I can go for hours with no problem. Doesn't seem to be related to when the aircon is on or even to the outside temp as it can do it at 6am. But with summer coming on I don't want to end up stuck somewhere.

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Suspects:
Water pump belt slipping.
Crook temp gauge.
Fans not kicking in.

Is it overheating to the point where hot coolant is forcibly ejected from the radiator overflow? You really haven't outlined the symptoms very well. If it is the temp gauge, look at what the fuel gauge does at the same time, if both go up together, its probably voltage related.

Jimbo, yes fan kicks in to the point where it runs on for so long after turning the engine off that it has flattened the battery twice in recent times. I am not sure about the second speed on the fan. How can I tell or test that?
Max, the temperature gauge seems to be erratic. When I get out of the car it often smells and feels hot. The needle doesn't follow the petrol gauge. It can be fine on a hot day yet get hot on a cool day at 6 am. There is no rhyme or reason to it all. Sometimes if it is hot I can put the aircon on and the needle will drop. Belt on the pump is tight and is not wearing as it would if slipping.

Tools:
We had a TM and although it never overheated, we did have a cracked head. It started to leak - eventually I found it was a hardened O ring on the water pump casing, but I thought it was a head gasket, so I removed the head. Then I saw the crack in the camshaft bearing journal. I got it welded up and line bored and it was all fine, but until I did that it was using 1 L of water per 100 km.

The way I would detect a cracked head is to remove the rocker cover and see if you have whitish sludge in the oil.

is it overheating or is the temp sender playing up giving false readings
i think the best thing for you is to take it and get a pressure and chemical test

Guys what are your thoughts on aluminium radiators compared to traditional copper/brass?

Guys what are your thoughts on aluminium radiators compared to traditional copper/brass?

Aluminium is a better conductor of heat but in a correctly functioning cooling system you wouldn't notice the difference.

Thanks Max, They seem to be a lot cheaper than traditional ones on eBay

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