itchyfeet wrote:Some questions
did you bleed the system thoroughly? airlocks can cause temp sender to read wrong.
How long before it shows overheating? driving and idle
when the temperature guage shows hot have you tried touching the bypass pipe across the gearbox, the metal return pipe to water pump and the rad return above thermostat and see how hot they are?
I've tried yo get all the air out, bleed on rad & thermostat.
Everything appears to be getting warm, barring the radiator pipes & rad itself of course. I haven't checked all you've suggested though. I'll check next time it's running.
I've done all the testing on fast idle + the temp gauge just goes up slowly & keeps going.
chewbacca wrote:
Further to this, I've discovered there should be additional water reservoir behind the number plate! I don't have one of those!
I'm guessing it should be there & attached to the cap of my existing header tank?
Yes, there should, but the lack of it won't be causing your immediate symptoms, so one thing at a time, that can be the next job to do
chewbacca wrote:Everything appears to be getting warm, barring the radiator pipes & rad itself of course.... the temp gauge just goes up slowly & keeps going.
Perhaps it is time "we" considered the water pump then? (I have seen one once where the impeller had parted company from the shaft )
Resistors in the temp plug worked a treat. As per those values I found.
Sender in a pan of water seemed to match the gauge, with water temp at 100 degrees being around about the center of the temp gauge.
Next thing, I've removed most of the redundant air con piping, I can see the wood for the trees now.
I'm pleased to report it was completely independent of everything.
Next item of note, the thermostat casing. I have put a new sender in for the temp gauge, in the hole facing towards the back wheel. Is that right? I ask because I have tonight found another sensor exactly the same, facing towards the front of the car, with nothing on it! Basically there's 2 senders on the thermostat!
ghost123uk wrote:
Perhaps it is time "we" considered the water pump then? (I have seen one once where the impeller had parted company from the shaft )
I'm not sure. Last time I was trying to bleed the system, there was a positive spout of water out of the rad bleed hole. I guess it could have been pressure, but I don't think so.
Also, when looking into the header tank, there's water movement out of the top pipe.
Is there flushing guilds anywhere? Maybe that's next if I've not messed up the thermostat wiring
chewbacca wrote:I have put a new sender in for the temp gauge, in the hole facing towards the back wheel. Is that right? I ask because I have tonight found another sensor exactly the same, facing towards the front of the car, with nothing on it! Basically there's 2 senders on the thermostat!
They should not be the same, though off the top of my head I forget the colour codes. One of them is for the gauge, and the other is a switch (not a sensor) that turns the carb's manifold heater off when the engine warms up.
chewbacca wrote:
There's not really any electrics in the cooling system is there?
No, not really, but...
Are you sure your engine is overheating and it's not just a gauge error? In this weather it does take quite a long time for the read to warm up. I'm not saying it's not overheating by the way, just kinda thinking out loud I got an Infra Red temperature gun a short while ago to check the temps on my engine bay cooling pipes (my gauge was reading a bit low = turned out to be a duff stat).
This thread is getting a bit "scatter gun" now Perhaps it might be prudent to go over your overheating symptoms again? (in a concise way )
Temp gauge not working. Found the relevant wires & attached to a new sender, which has probably been fitted into the wrong hole on the thermostat housing as I didn't realise there was a sender & a switch in the housing. (neither had connections)
Engine was run on the driveway & overheated. Bleed valve on the rad & thermostat housing were both pushing out water, but radiator is cold to touch when engine is over heating.
New thermostat fitted. Exactly the same result, still cold radiator & overheating.
New temp sender tested in a pan of boiling water & appears to be fine. Temp gauge tested with resistors & also appears to be fine. Hopefully this means the gauge is reading correctly.
All the old air-con removed to ensure there's nothing weird going on there. There wasn't.
So to sum up....
Engine overheating.
Temp gauge probably ok, tested as much as possible.
Water pump probably ok as there is some evidence of water flow.
Thermostat ok as it's new & was tested in boiling water before fitting.
Current plan....
Flush out the radiator
Fill & bleed the system
Cross fingers
Run engine & see what's what. (check I'm getting warm air out of the heaters)
Temp sender & temp switch removed just to check they are in the same place internally. They are.
Rad return hose pulled off of the top of the thermostat housing & out hose to rad front the distribution plastic thingy. Pipes & rad flushed through. I don't think there was a blockage.
Return hose left off & engine started. Hose pipe into header tank. Lots of water out off rad return pipe. This I'm hoping checks the water pump as well.
Unfortunately I'm out of coolant, so had to stop there. (see my other thread about coolant )
I did sort the wiring out mind, so that's a result. Shame it's unrelated.
jason k wrote:Two things!
Either a "pooh" stat! Only ever use brickwerks ones
Or
Blocked rad (very common)
Had identical issues on a mates van. The old rad weighed twice as much as the new one!
It was full of flag and silted right up
Thanks for the post. All help is great!
My rad seems fine after tonight's testing so hopefully it's not that.
The fault was there before the thermostat was changed & I tested the new one in boiling water first. I'll be disappointed if its that now.
)
Perhaps it might be prudent to go over your overheating symptoms again? (in a concise way 
)