DB 990 getting hot, but radiator is cold?

[Exfarmer]

No it is in quiet good and clean condition on the outside. I was thinking of trying without the thermostat, but got adviced against it because the thermostat is restricting flow, so the time the coolant is at running through the block needs to be low enough for the coolant to absorb the heat. If the thermostat is not present, the coolant will flow to fast and result in the engine running too hot. But what is right and wrong is beyond my knowledge, but thats why I have not done it yet.

that is going against the laws of physics
heat will pass through any substance according to the temperature gradient, the greater the difference on the two sides the faster heat will flow.
Thermostat out would be my first thing as well as a good radiator flush.
However I suspect you need a new water pump

 

[JacobJ]

Black stuff is residue from combustion gasses

So you say that it is the head gasket? The glove trick, would that be a way to show that as mentioned before?

 

[JacobJ]

that is going against the laws of physics
heat will pass through any substance according to the temperature gradient, the greater the difference on the two sides the faster heat will flow.
Thermostat out would be my first thing as well as a good radiator flush.
However I suspect you need a new water pump

Okay, so out with the thermostat, thats one thing I could try. Glove trick another. New radiator cap is also easy. I have thought of taking the top hose off and replace it with a transparent piece of tube. That way I could see if there is flow with the engine running?

 

[suffolksmallholder]

that is going against the laws of physics
heat will pass through any substance according to the temperature gradient, the greater the difference on the two sides the faster heat will flow.
Thermostat out would be my first thing as well as a good radiator flush.
However I suspect you need a new water pump

+1 for water pump.
And when you do fill up for the final time put at least 50% of GOOD quality antifreeze into the system.
SS

 

[010101]

The cab heater will tell you about water pressure either side of the pump. The water pump is what pushes the hot water through the cab heater.

Fill it up and run it with the expansion tank cap not fitted, so that the water galleries don't pressurise when the water first expands when warmed from cold.
If it stays cooler for longer it is probably a cylinder leakage boiling the water and the cap waiting for the overpressure before venting the steam (like it should).

 

[JacobJ]

The cab heater will tell you about water pressure either side of the pump.

Fill it up and run it with the expansion tank cap not fitted, so that the water galleries don't pressurise when the water first expands when warmed from cold.
If it stays cooler for longer it is probably the cylinder leakage boiling the water and the cap waiting for the overpressure before venting the steam.

I dont have a cab heater. I dont have a cab at all;D

If I understand you right. Off with the radiator cap, run it and if it stays cooler for longer it may be the head gasket? How is that, that it will be colder for longer with the cap off?

 

[010101]

I dont have a cab heater. I dont have a cab at all;D

If I understand you right. Off with the radiator cap, run it and if it stays cooler for longer it may be the head gasket? How is that, that it will be colder for longer with the cap off?

Because it let's the steam out before it overheats the rest of the water jacket and airlocks (I know steam is not air, it is a turn of phrase) the flow through the rad.

 

[JacobJ]

Okay. But would the glove trick mentioned before not show the same? To night I have a lot of things mentioned in this thread I have to check. But thats better than being clueless..hehe

 

[010101]

Okay. But would the glove trick mentioned before not show the same? To night I have a lot of things mentioned in this thread I have to check. But thats better than being clueless..hehe

The glove will show you the water jacket is pressurising before the water is doing it with thermal expansion.
Removing the pressure cap will de-pressurise the water system.
If it works to delay the overheat you know your problem is overpressure not underpressure from a bad pump.

 

[Oliveau]

The cab heater will tell you about water pressure either side of the pump. The water pump is what pushes the hot water through the cab heater.

Fill it up and run it with the expansion tank cap not fitted, so that the water galleries don't pressurise when the water first expands when warmed from cold.
If it stays cooler for longer it is probably a cylinder leakage boiling the water and the cap waiting for the overpressure before venting the steam (like it should).

OP has a DB 990, so;
Cab heater - I don’t think so
Expansion tank - I don’t think so

New rad cap is cheapest so try that first.
I think water pump is most likely

 

[010101]

OP has a DB 990, so;
Cab heater - I don’t think so
Expansion tank - I don’t think so

New rad cap is cheapest so try that first.
I think water pump is most likely

What do you think the rad cap does?
If there is not a separate expansion tank, the top tank on the radiator acts as one.

 

[JacobJ]

What do you think the rad cap does?

As I understand, and the reason I also thought it was worth trying is, that it lowers the boiling point, so the coolant can recieve the heat faster/better. Is that incorrect (too)?

 

[010101]

As I understand, and the reason I also thought it was worth trying is, that it lowers the boiling point, so the coolant can recieve the heat faster/better. Is that incorrect (too)?

Increased pressure raises the boiling point of water. The thermal conductivity does not really change significantly at the sort of pressures found in a diesel engine cooling system.
On Mount Everest the boiling point of water is 68C.

 

[Pistonbroke]

As I understand, and the reason I also thought it was worth trying is, that it lowers the boiling point, so the coolant can recieve the heat faster/better. Is that incorrect (too)?

Just to be clear,are you sure it's overheating, temperature wise,or are you assuming it is because it is blowing water out? Could just be the cap is leaking out when the water expands

 

[JacobJ]

Just to be clear,are you sure it's overheating, temperature wise,or are you assuming it is because it is blowing water out? Could just be the cap is leaking out when the water expands

Well, the temperature gauge is all the way up in the red zone (maxed out). So I am sure that at the position of the thermostat it is hot.

 

[Alchad]

For heavens sake, as I suggested yesterday, take the water pump of and check that, it’s the most obvious candidate to be causing a problem, discussing it on here isn’t going to get you any closer to sorting.

 

[egbert]

You've flushed the radiator internally so I'm assuming You've cleaned the outside? Can you see through it ,are the fins flattened and blocking air flow? Try running it for a few days without the thermostat fitted , won't do any harm. Water pump could be knackered without showing any external signs ( no wobbly fan or leaks )

can't remember when I last ran a 4 pot browner WITH a thermostat

 

[egbert]

Right, without reading every post...

DB getting hot.
Is outside of rad clean of debris? No? clean with compressor.

When gauge is showing hot, is block/rad hot to touch? Block hot /rad cool, water isn't circulating.

Take rad cap off - carefully not to scald yourself, obv. Is water flowing into top of rad? (DBs are obligingly easy to check).

If not, is fan belt tight enough to spin water pump? Is thermostat stuck shut...?(throw it over the hedge) Or is water pump knackered?

Having got this far, and still overheating? Ask someone cleverer than me.

 

[Bald n Grumpy]

Well, the temperature gauge is all the way up in the red zone (maxed out). So I am sure that at the position of the thermostat it is hot.

Don't trust the gauge I've got 2 DB,s that constantly run in the red even when it's freezing weather. When it gets into the red VERY CAUTIOUSLY release the radiator cap , usually 1/4 turn will let you see if it's going to blow hot water at you. If you can dip your finger in the hot water it's not very hot IMO and you probably have a faulty gauge not a overheating problem.
Never worried about not having thermostat fitted and rad caps are always slightly iffy here.
Step1 check you have a overheating problem
Step 2 remove thermostat
Step 3 check water pump is circulating water ( look in top of rad when running without thermostat fitted)
Check for play in pump by pulling on fan blades.
If taking thermostat out or replacing pump doesn't fix it think about the head gasket.
What are you using the tractor on when it's overheating, is this now or summer time?
Just seen @egbert post so sorry for doubling up, agree with him

 

[JacobJ]

Okay I am overwellmed with all the good feedback here. I am back from the garage and here is my progress:

1. Glove didnt inflate.
2. Took the thermostat off. Will stress test the tractor tomorrow when there is light outside.
3. While I had the thermostat out and the top hose off, I cranked the engine and it shot water out from the thermostat housing telling me, that the water pump is working.
4. Checked the oil stick, and the oil is black as in my car, so I dont think water and oil has mixed. Combustion to water is still a possibility I guess.

I will get back to you after the stress test tomorrow to see if that did the trick taking out the thermostat.