Radiator woes

I am running a Perkins 6354 in a Bedford SB3 bus and am having issues with radiator coolant loss. The radiator is new and the water pump and thermostat are also new. The engine is strong having been recently rebuilt. Despite this I am continuously loosing coolant and having to top up each day. This can be anything from 2-4 litres. I do know that when I stop after a run that I am losing fluid out of the radiator overflow although don't know if there is loss during the run. The water temp is showing as reasonable varying from 74 - 90 degrees depending on outside temp and road style, flat, inclined etc. Similarly block temp remains good generally at a slightly cooler temp then the water, 75 - 85 degrees. I have replaced the bottom radiator hose and assume that the top one is OK as the radiator was replaced by a Natrad radiator centre. I know it is not always wise to assume but surely they would have noticed that the hose they were connecting was damaged and suggest replacement. There is no overflow tank currently fitted to the radiator and I have doubts about the cap fitted to the tank and would like to know the following:

Would an overflow tank be recommended?
What pressure cap should be fitted to the radiator?
Any other suggestions to solve my problem or is it just something I have to live with.

Sounds like compressed gas in the water.A 354 should run OK without any radiator cap,provided a bigish top tank.The early 354 (ie 354U xxxxxx .eng no) has no oil cooler,the water pump has ball bearings and a very common seal,no press fits,all keyed,easily rebuildable.Sounds like old father time has overtaken your perk,and the head /block surface is corroded,or a casting is pinholed thru.As to temp,it is in fact pretty high,ok for a modern,not for a perk.Take out the thermostat,and see if the circulating water is full of bubbles ,or foamed.I reckon 60deg is plenty hot enough.Perks used to be commoner than BS at a truck rally.Im in Brisbane,if you want to look at rusty perk bits.......As I remember ,I used to peel the rubber out of all my Inter Perk radiator caps. PS ... the old guy down the street says"Perks made me rich......Macks made me poor again"

S.Poke, for all the woes with my tired old perk, water loss is not an issue. I wonder if the new thermostat could be a problem. I needed a new one to get my temperature UP, to reduce the blue fog following me around. Running around without one for a test might be a good idea, and a recovery cap and recovery bottle will only improve your information about what and when your loss occurs.

Keep us posted.

Wrong or faulty radiator cap?

Like overnite said, I would be looking at the radiator cap

How sure are you about the rebuild? If she's overheating in these ambients, you'll have real problems come Summer.
What type of fan does it have. Often a bus will have been modified over the years and the fan or cowl may not be up to the job.
Does it have a viscous fan drive? They're a real trap when they get old.
I can't see an overflow tank or radiator cap helping, should run fine and not need 4L per day even with no cap. That's a lot of coolant to lose, must be getting low in the top tank.
Think you've got other problems.

I would look at radiator cap first, to rule it out. Maybe someone has fitted a recovery cap instead of a closed system one at some time ?

Radiator cap is clutching at straws
As John has said they should run nice and cool even when working hard
If you are loosing that much water and it's getting hot I would be looking for sure at compression getting into the system
Is it a corroded block or a buggered head, I have no idea with any luck just a head gasket

While your wasting time changing radiator caps and hoses and other stuff like that summer is getting closer

These 6554's should run at less then 70 when working hard, you have changed the radiator and the motor has recently been rebuilt, there's a lot of clues there to were the answer will and will not lie and the radiator cap isnt one of them

Paul

Is the radiator a direct replacement ?
Is the top tank the same height as the old one ?
If the thermostat is working maybe try running the front of the bus up some
ramps stick a funnel into the neck of radiator and keep it topped up with water
until the thermostats opened to get any air trapped out of the head.

There is a problem now with any old diesel,and that is head gaskets.Modern replacements for asbestos often arent suited to old engine design.Solid copper gaskets are a waste of money with diesels.However ,assuming there isnt any compression leak,the next thing I would look at in a conversion is air flow thru the radiator.Is the fan a mile from the core,or well offset.An effective fan shroud may be necessary.Sometimes hot air can recirculate back in front of the rad,due to body design.Not common in a vehicle.Where is the fan mounted? Crankshaft fans often have rubber hubs that fall to bits without it being noticed.You might have to install electric fans.