No coolant flow after heating up the engine

[Weinigstress]

Hi all,

I rebuilt the engine on my 2002 Ford Transit 2.4 TDDi (previous owner overheated it).

Symptoms so far:
• Heater circuit works fine – cabin gets hot quickly, so water pump is circulating.
• Thermostat has been replaced twice with new ones.
• Water pump replaced as well.
• After idling for 30 minutes, both radiator hoses remained cold.
• After driving 4 short rounds of ~1 km, the top radiator hose felt hotter than usual, but the bottom hose stayed completely cold.
• Expansion tank still shows no return flow.

Concern:
It seems coolant is not entering the radiator at all – as if the thermostat doesn’t open or the radiator circuit is blocked.

Questions:
• Why would the thermostat not open, even after idling and short drives?
• Could the radiator itself be blocked, or is this more likely air trapped in the system?
• How can I safely confirm coolant flow (or lack of it) through the radiator circuit without risking another overheat?
• Is there a known bleeding procedure for the Transit 2.4 TDDi cooling system?

Thanks in advance for any advice!

[metalworker0]

What country are you in, what was the temperature there.

Below 5c these things can tick over for an hour and never reach operating temperature and need 5 miles (8 kms) at least to reach running temperature . leave the cabin heater on blowing and it it will take 7 miles (11 kms) to reach temp.

all the best.mark

[Weinigstress]

Netherlands. I have been working / trying in conditions like 18 / 20 degrees celsius. But with hood open and wind blowing kind of strongly when trying stationary. When driving i did 4 rounds of 1 km. Going up to 4th and 5th gear regularly. The car temp needle on the dashboard did not go to half, but was more around 35% and kept stuck on that temp even after another round.

[tranmx2]

Heater circuit works fine – cabin gets hot quickly, so water pump is circulating. It'll take longer for the engine to reach operating temp' with the cab heater giving off heat. 30 C in the cab may seem hot to you. Some cabs are open to the load bay some are paneled off from the load bay. The 2012 is open to the load bay.


• After idling for 30 minutes, both radiator hoses remained cold. It takes about 7 mins for the 2012 Transit to reach operating temp' ( depends on wind speed/direction and ambient temp) going mostly up hill in 3rd gear at 1000 to 2000 rpm. At another place it takes about 4 mins due to it being up hill in 2nd gear then for a couple of mins in 3rd also uphill.

After idling for 30 minutes, both radiator hoses remained cold. Could be due to the cab heater lose of heat the engine coolant has not reached the temp' required to open the thermostat. The 2012 thermo opens at 88 C.
Could also be due to the thermo not fully closing - some heat is lost but not enough that it can be felt on a pipe. The feather that breaks the donkeys back.

The thermo on the 2012 has a built in bypass which allows warm/hot water to pass more directly to the coolant inlet circulating pump inlet and to the EGR cooler and cab heater. There is also a vent to the header tank from the thermo and from the radiator top part.
Usually cannot see movement within the 2012 header tank.

The 2012 shows about 65 to 75 at operating temp using Forscan live data. The sensor for the guage is under the thermostat. The middle of the guage - needle vertical - could idicate 90 C - the temp gauge on the 2012 is usually just above the mark before TDC (needle vertical position) the mark could indicate about 75 C.

[andz327]

Make sure the small hose to expansion tank and the parts it goes onto isn't blocked especially the expansion tank end as the small metal insert blocks easily if stop leaks have been used and wont circulate and bleed properly

Sent from my SM-G990B using Tapatalk

[vansit1]

can you post some pics of the engine and water pump if you have worked on them and where is the small oil cooler thermostat connecting to? it might be broken up with some part gotten stuck somewhere, and where is the coolant level at in the bucket?

[Weinigstress]

Today I tested with a longer drive 20km normal road and 10km highway. The engine is running smoothly. Stopped multiple times in between to check engine heat and hoses. Thermostat opened, pressure came out and let some extra air out of the coolant reservoir. The top hose above radiator was hot, lower hose semi warm, soo is cooling properly right? Do notice that the coolant reservoir is not included much in the flow. Guess this is normal for a car from 2002?

One thing to note is that my dashboard heating indicator doesn’t go higher then 1/3 of the range and remains there. Im thinking of a defect cylinder head heat sensor. I already have a new one laying since i changed the cylinder head. I used the old sensor, but will replace to see if it helps.

My thinking is that the ecu doesnt register the heat of the engine correctly and therefore on the long run will perhaps not activate the fan correctly? Or is the radiator fan not connected to this sensor?

Thanks for helping me out with your advice.

[vansit1]

there was several questions already