radiator hot on top bottom hose cold.

afternoon gents, drained my cooling system to change crank bottom pulley.
all back together cooling sytem filled and bleed as lz threads.
my son has used it for the past month run fine before the repair. however when i used it last the temp gauge needle sat halfway and never moved, now needle sits at half way to half.(colder weather}.
gave it a 10 mile run checked for leaks and ok.
the bottom hose is cold top hose hot but not too hard with pressure. slowly cracked header cap and not a great deal of pressure
quite happy to throw a new radiator and stat on it but not to find it is fine and just not getting hot enough to open stat. i worked it quite hard for 10 miles. would not like to drive it further incase engine cooks. i have never checked wether rad was cold on bottom after a run before.
any advice would be very welcome.
regards garry.


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What engine ? Cool bottom hose is fine. In colder weather 10 miles is only just enough to get up to temp for many vehicles.

Thermostat may have failed and stuck in full open position, not allowing engine to maintain temperature.

tottot said:

What engine ? Cool bottom hose is fine. In colder weather 10 miles is only just enough to get up to temp for many vehicles.

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hi there td5 p15, 06 year.
thanks for your advise, just flapping about cooking my pride and joy.
kind regards garry.

Scooby22 said:

Thermostat may have failed and stuck in full open position, not allowing engine to maintain temperature.

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but if it was open then some heat transition would occur and bottom hose should be at least warm.
my l200 truck is warm after 3 miles both top and bottom hoses warm, not sure what the stat opens at thought.
thanks for taking the time to reply scooby.
garry.

hmmm changed stat today, temp on gauge where it always is, heater air hot, hoses not pressured.
45 min run top hose hot bott cold.
hose to stat bottle hot bottle cold. i cracke open header cap not much pressre, header tank warm fuel preheater hose cold. bled it to death.
never checked cooling hoses before so is cooling system that effecient.
no bubbles in header tank, regards garry.

Sounds like my own, I wouldn't say the bottom hose is cold, but it's only lukewarm after a good run - and I don't have a fan - haven't had one since installing the TDi years ago. I can only get the bottom hose to become warm after a long motorway run. The engine/cooling system is designed to cope with towing in hot climates, so it is over specced for this country.