Hi All, its been a while since iv'e posted any topics on here,my dozer has been going fine for the last 2 years up until recently.While using it about a month ago,it starting getting hot,the temp gauge was up to 3 quarters and the water pressure gauge went nearly as far as it gos,water started spewing out of the radiator cap.I parked it up as soon as i could and let it cool down.I did notice water seeping out near the water pump.The following weekend i filled the radiator up again after it took 30 litres of water to top up and drove it for a short time and noticed the water pressure going right up and the radiator cap spewing coolant out again,parked up again but no leaks around the water pump.
So now i'm looking for a fix,hoping its not the head gasket or worse.I will replace the easier possible causes first
I can buy a new radiator cap (8H-6714) $271. from my Cat dealer. 
I need 2 regulators(thermostats)(4L-7615),no luck online from Cat,so would anyone know the replacement number.
The water pump(1S-1684) will be next and not sure where i can get one of them or whether i can get it reconditoned.
The radiator looks in good condition and clean coolant so i don't think its that,the fan belts are slightly loose but don't seem like the belts are slipping.The next thing would be the head gasket but i don't want to even think about that yet.
The dozer is a  1964-5 D7e low horsepower model and i live in Western Australia,so parts ar'nt the easiest to get for an old machine and it seems like the Cat dealer does'nt stock many parts for them any more.
Anyway i hope someone can give me an idea of why it might be overheating ,cheers John.    

If the radiator bee are clean it could be the fan bell or pully or could be too the radiator is plogged before removing the head

I'll have a closer look at the radiator,the fan belts are definitely a little loose,although they have been in the past and no overheating before now.Removing the heads will definitely be my last attempt at keeping it cool,cheers mate.

Check thermostats in a pot of boiling water. Radiator is probably full of dirt . Possible chance of bad precup? Had a  8K D8 that need 2 hours with a fire hose to clean radiator and tighten belts so fan would keep air flow to keep it clean.after that all was good.

Different era of engine from my D6 9u, but increased pressure in cooling system on it is most likely combustion gases leaking by the pre combustion chambers. But with a newer designed engine I may be sending you the wrong direction. So those that works on this series engines can say better.

First check would be the precombustion chambers.

Are you seeing bubbles/air at the radiator fill neck (signs of compression leakage).
Sounds more like a clogged radiator. Get one of those cheap infra-red gun thermometers and report findings, particularly top and bottom radiator tank temperatures.

I've got an infra red thermometer gun and i'll let you know the readings.When its running and starts warming up,it starts to leak coolant around the base of the cap,i guess its starting to pressurize and letting out pressure where it can.The cap has had a rubber seal made by a previous owner so probably does'nt help.Should i keep the cap off for a little while when first starting up and look for air bubbles before it builds pressure.The cap does'nt match the correct part number although it does look original and have'nt had overheating problems with it before.I'll let you know how i get on with it,cheers.

Your unit should have a sealed pressure overflow (separate from the filler). It should relieve a 6 psi when necessary and break vacuum at 1 psi when cooling. Make sure the drain line is working. Yes, check for air/bubbles at the filler as it comes up to temperature.
 

   Did you mean the valve on top of the radiator as shown circled in red on the pic Old Magnet, or the overflow line circled in blue .The valve on top looks like it hasn't been removed for years and a few coats of paint over it. I have looked up part numbers from Cat and it looks like they have stopped stocking alot of parts for the old dozers. I can only find the radiator cap listed.Do you know of any places to buy genuine parts or is it all aftermarket for the old dozers now.I'll have a look on Sunday and fire it up,its on a block an hour from my place so i'll have to wait till i get a day off,cheers.