High Temp Reading

[Dolly-Nut]

Hot. I just changed the stat and it's the same.
Even though the water pump impeller and seal is new it's still leaking and using water and the hoses are getting hard within a few minutes. It also has a rough idle and is chuffing a bit of smoke - Headgasket? Would that cause it to read high on the gauge so quickly?

[Dolly-Nut]

If the cooling system is being pressurised I guess that's the cause of the water pump leak but still, I wouldn't suspect the gauge to read that high so quick.

[GrahamFountain]

What about a blockage? Might explain why the pump still leaks if the back-pressure is excessive - incompresability of water, etc. I take it the radiator was radiating recently.

Graham.

[Dolly-Nut]

Well water pours through it....

[GrahamFountain]

Think I'm out of suggestions then.

Graham.

[Dolly-Nut]

I'd like to test the temp gauge wiring since it's the only thing left really. Whilst it was running earlier and the gauge was over 3/4 I could easily hold the bottom hose and touch the head. It wasn't even luke warm.
I tried running a wire straight from the sensor to gauge (correct side) and got no reading, does anyone know why?

[djw113uk]

Apologies if any of this is teaching you to suck eggs, but these are my thoughts:

I guess you machined the underside of the impeller so it didn't just chew up the new graphite seal? Should be a shiny machined surface, with no surface rust or roughness. I have had lots of problems with 12v impellers spinning on the shaft. 6v don't seam to. I clamp shaft softly in the vice and try to turn impeller - they shouldn't rotate separately!

I also managed to crack the graphite seal on one refit into my stag. Didn't leak much, but it did leak.

I have never known a water pump leak due to head gasket issues. Maybe as well as, but not because off!


How much have you driven / thrashed it? If it is on "original spec" pistons these can break down around the rings - through the use of unleaded. This leads to lots and lots of smoke. Our rally sprint did it. No coolant issues though, just very very smokey!

Thermostat should look like this one...FTS153.88 (pic attached I hope!) with the foot. Always worth boiling up even a new one to see what temp it opens at. The new one we bought first didn't open until 100 degrees. Luckily I tested it before fitting! To be fair most seem to open too early not too late. The little jiggle pin is just to allow air to escape. It should be present, else drill a 4mm hole through the flange. Lack of this would leak to air locks.

I also have found that very often when first re-starting the water 'air locked' big time. Turn off, squeeze hoses and fill slowly and all tends to be fine. For some reason newly built pumps seem not to like priming and pumping!

I assume you have correct water pump cover on the correct impeller - 12 / 6 vane? And have put the correct number of gaskets on the cover to create the right clearance? Odd that this needed doing again so soon - didn't you have to do the waterpump before bringing it home?

I have a digital lazer thermometer - £25 from Maplin. Point the lazer at something and it tells you how hot it is. Just watch as cheap ones are not measuring the dot, but just below it! Stat housing should be 85 degrees when temp gauge is central, but it is not a linear scale.

Is your fuel gauge correct? Voltage stabiliser can cause both to read wrong. Be worth swapping for another (just above fuse box) and see if it make any difference) better still read the output and see if they are the same and what the reading is.

If hoses go hard quickly it is most likely water pump not working properly - cover clearance, wrong cover, impeller slipping etc. Or an air lock. Head gasket may cause it to pressurise but not usually that quickly at just idle!

Need to work out if the gauge is just wrong, or it you really have a problem. A thermostat not opening would still take some time to show as overheating in this cold weather!

[Jon Tilson]

If your water pump is leaking out of the slot even though it has a new seal then something is wrong.
I had this recently and it was a chewed jackshaft gear that was making the pump ride up and touch the cover.
It wasnt cheap to sort as it needed a new jackshaft.

Mind you it wasnt the temperature gauge that was the issue - it was the din....

You still need to sort the leak whatever.....and if hoses are pressurising but not hot then it can only come from
the combustion process....leaking head gasket. Which kinda goes with the smokey exhaust.

Still - do all the cheaper things first to be sure. Water pump guide here just in case...

https://www.dollywiki.co.uk/wiki/Water_Pump_Overhaul

Jonners

[Dolly-Nut]

Don't really know where to go with this. I'd still like to test the wiring to the gauge, can anyone answer my previous question regarding a bypass wire not doing anything? I'm going to try that again tomorrow with yet another sender just to check, again.

The impellor i fitted yesterday was brand new and perfectly flat. The seal also looked perfect and was renewed when I bought it less than 500 miles ago. It could well be a knackered jackshaft but then I checked the pump cover and there were no signs of touching. Yes it's the right cover (only the correct one can be fitted) and it's gapped correctly with my grease method. I will strip it again I guess and see if I can spin the impellor if the gauge continues to read high.

I have tried numerous voltage stabilisers and the fuel gauge is correct.

Just had an idea actually I'll get some warm water and dunk the sensor in it and see where that gets me.

[Toledo Man]

Did you try earthing the wire that plugs into the sender? If everything is fine the gauge will go all the way to the red.

[Dolly-Nut]

Yes and it did.

[Jon Tilson]

Are you sure the leak isn't coming from the bypass tube?

You say your hoses seem to pressurise pretty quickly, yet dont seem hot.

I had that on a car when the stat was not opening. But you've changed that...

Did you check it opens in a pan of hot water?

It sadly sounds like it must be the head gasket. As you say you cant see any sign of contact with the cover and
I assume there is no noise?

Jonners