Loose radiator cap, potential overheating

[Greenbeast]

As a few will know the old zetor had a top end rebuild earlier this year. Subsequently expecting it to be 'good as new ' I have been a little disappointed to find it close to 100 degrees after short periods of post knocking (an hour or less say)
The rad cap is obviously loose given it's age and the over flow channel rusted open to nothing.
I don't appear to have an obvious leak and have not witnessed it steaming yet, always being careful to stop work as the temp gauge goes above 90.

What to do about this?
Is a loose cap unhelpful in this situation?
I can't get my head around the pressure/temperature consequences

 

[Pilgrimmick]

The higher the pressure the lower the boiling point, so a loose cap will not allow the build up of pressure and the coolant can boil easier.
However, if there is no steam and no fluid loss then it would seem that this is not the problem.

 

[Greenbeast]

The higher the pressure the lower the boiling point, so a loose cap will not allow the build up of pressure and the coolant can boil easier.
However, if there is no steam and no fluid loss then it would seem that this is not the problem.

That's kinda where my thinking was.
I will be running it again on some post knocking soon, I will keep an eye on fluid levels to check

 

[Greenbeast]

That's kinda where my thinking was.
I will be running it again on some post knocking soon, I will keep an eye on fluid levels to check

I'm curious about heat build up if I make sure the rad is topped up before I start. Perhaps water pump then?

 

[Pilgrimmick]

I'm curious about heat build up if I make sure the rad is topped up before I start. Perhaps water pump then?

Depends on system, often if water pump gone then the indicated temp is low, as water not circulating and temp sensor is in the cold part of the system.
Check oil temp as this should give a good idea of what is happening.

 

[Greenbeast]

Depends on system, often if water pump gone then the indicated temp is low, as water not circulating and temp sensor is in the cold part of the system.
Check oil temp as this should give a good idea of what is happening.

Hmm don't know if i have a working oil temp gauge...

The return to rad is hot so I guess water is circulating

 

[roscoe erf]

Is the fan and fan belt In good condition right tension has the fan been put back on the right way

 

[Greenbeast]

Is the fan and fan belt In good condition right tension has the fan been put back on the right way

Belt is new (after dynamo to alternator switch). Will check tension.
Can feel air coming towards the engine from it so assume direction correct

 

[Mursal]

Yes the higher the pressure the higher the boiling point, so the coolant stays as a liquid longer. But tipping about the rad cap shouldn't be necessary.

If the cylinder were touched (new rings and or pistons) it may well run hot.
If you can have a wee look into the corners of the radiator (outside) it might be a bit blocked?
If radweld or the like was used to help with the leaks before getting the work done, it may well have the radiator partially blocked inside.

Fan on in the correct direction, pulling air through from the front of the radiator?
Thermostat a bit lazy to open?
Water pump not turning the impeller

 

[multi power]

I'd put a couple of scoops of washing powder in the rad, get it hot and flush it out

 

[REStracTORATION]

When the temp gauge is up to 90
Stop tractor and check hoses is the top hose blistering hot or acceptable.
with bottom hose if its cold suspect thermostat then water pump if stat is ok

The rad could be blocked if sealer has been used in the past or head gasket gunk!

Could also be the sender reading high is gauge fully down on its stop when cold??

Always check the simple things 1st if you can

 

[TripleSix]

There is something wrong because it shouldn't get that hot running a post knocker.

A loose rad cap doesn't make an engine overheat, it just lowers the boiling temperature of the coolant.

 

[DrWazzock]

Thermostat? Either take it out and try it in a pan of water on the stove or just fit a new one as a cheapish elimination of that possibility.

I'd flush the system and clean the rad as well on a tractor of that age.

 

[DrWazzock]

If you leave the cap off when cold then warm up the engine you should see flow into the tank as the thermostat opens if it is opening.

 

[TheTallGuy]

Check the actual temp with a thermometer - either the sender or gauge could be out of calibration - especially if you are not seeing any steam. A cheap non contact sort like https://www.amazon.co.uk/gp/aw/d/B0...ermometer+non+contact&dpPl=1&dpID=41zHfluSX0L should do, take a reading from a kettle or pan of boiling water & then compare to the tractor.

 

[mikep]

If it gets too hot it will boil. A good cap will help prevent that but allow for escape of pressure if overheating.
It takes a lot of overheating to kill a diesel especially if you are looking for it.
Give it a new cap and some work and see if it boils.