Has anyone got any suggestions when I got my k74 I did a coolent change as it was old and untouched, however the heating then stopped in the truck
I have looked on some pages and found some tips, so today we flushed the system and topped it up by jacking the truck up and pouring in slowly, the top hose was removed untill the fluid poured out and then re connected it. Left the truck to warm up leaving the rad cap off.

Removed the temp sensor as I have no idea where the bleed valve is.

Once up to temp switched on the heating which started off cool then got slightly warmer and then went cold again.

Before I did anything to the truck it all worked, so I thought it must be an air trap however after redoing it again today and having the same problem I'm gussing it's something else

Trying to feel the pipes in the engine they all feel fairly warm but not too hot too touch

Any ideas.


Thanks in advance

have you replaced the stat

I havent yet as it was all good untill i decided to replace the fluids

When I replaced my hg i had the same issue ... I would say you still have an airlock somewhere, took my 3 attempts to get heating working , I ended up removing the pipes to the matrix and giving that a good flush with a hose

Quote: A guest wrote in post #3

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I havent yet as it was all good untill i decided to replace the fluids

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Air lock is what im thinking

May change the stat and see what happens

jack the front up run with rad cap off and heater on hot that will move the air lock if there is one

I did that ran it up up to temp with the cap off etc


So i think ill chage the stat and see what happens then

money on the stat then if u filled it via the top rad hose i doubt it is a lock

Ill get one for saturday and see what happens. Ill post an update then Thanks :-)

Turns out an owner before me has removed the stat

Iv drained the system again and flushed it refilled as before However the bottom pipe is stone cold and the temp is saying its overheating

Still no warm air in the truck any ideas?

Can only be a blockage somewhere or major leak? No heat in heaters coupled with overheating stinks to me of an airlock or very poor circulation...hmm.. wonder if water pump is failing...unusual for them to go but you never know. I would also be wondering why stat was removed...

Could also ...possibly ... just possibly be rad cap not holding pressure so system isnt heating properly..or could be heater is unrelated issue?

After get annoyed with it and leaving it the levels dropped
I topped it up again left it to warm up again got bored reved it up a bit and all of a sudden warm air was comming from the vents.

So all seems to be working now
I felt the pipes and they are now pretty soild is this normal? As well as the bottom hose to feel cold?

sounds likeit was an air bubble/lock....

bottom rad hose will fill cold until the stat opens mine dont open unless pushed hard in the winter

Fair enough well seems ok for now anyways


Next abs issue haha 😂 (that got upset when the disc an pads got replaced)

Thanks for the replies on this :)

some one damaged a sensor

After working yesterday day its giving me issues.
Warms up like you would hope the moment you stop im traffic ot blows cold,start moving and its hot again.
When it did this the temp went up to the red,
Turned the heater off and the temp went back down to normal and then blows cold.


All levels are correct now and pipes go harder with the preassure

maybe the water pump is knackered ?

Id say viscous fan nackered

Water pump is going when i looked the other day could see the water flow changed with the revs

Both fans are working one when it gets hot and the other one that spins all the time

viscous should spin all the time but there is spinning and spinning, make the truck hot then turn the engine off and count how long or how many times the fan spins before it stops from the moment u turn the engine off

Not sure viscous would affect the flow of water to the matrix. ( i could be wrong ) . It deffo sounds like a circulation issue to me

So i was able to look at how many times the fan spins once you switch off the engine probs spins about 15 times max so not too many?

15 times too many it should stop dead