1983 110 Stage II V8 indicating an overheating issue

I bought this 110 V8 a few months back with the intention of using it and during the next year, returning it to full working order, while still in use. I have another car so it's not totally relied on for transport.

Right, to the problem.
The dash had a nasty aftermarket guage in it
There's an aftermarket Webber/Edelbrock combo in place of the two carbs
The heater matrix pipes from the back of the water pump to the matrix were not right (I'll explain later)
The heater didn't blow hot, warm or even lizard belly like temps
There are NO signs of the engine overheating, other than this indication on the guage
No water loss
No running on
No popping, bubbling or any other sign that the engine is not happy

This is the list of changes I've made to try and see what's going on.
1 - New temp sender and Thermostat - No change
2 - New guage - No change
3 - Drained system and flushed rad and heater matrix - No change
4 - Fitted correct thermostat housing and re-plumbed heater pipes
5 - Drained and reflushed system again
6 - Measured relevant areas with digital, laser thermometer

After stages 4,5 and 6 I was able to feel a slightly warm temp from the blower inside but the over heating on the guage continues.

Going back to those heater pipes and thermostat housing.
It took me a while but I knew those pipes were wrong. I'll try to describe it.
The pipe frrom the back of the water pump on the N/S went onto a metal pipe, under the carb and up onto the heater matrix, ok, that's right.
The other pipe went from the water pump, then into a 90 degree plasit bend then over the O/S bank to a T piece near the heater matrix. One side of the T went to the matrix and the other to the back of the Edelbrock manifold.

With all that off and back to normal and with the correct Thermostat housing fitted with the little pipe on the front that goes to the water pump, I now have that slightly warm blow. However, the over heating indication continues.

I came home tonight with this temperature tester and got it up to temp during the 25 minute drive home. This is what I measured:
Top hose (engine end) 76 Deg C
Top hose (Rad end) 61 Deg C
Bottom Hose (Eng end) 41 Deg C
Bottom Hose (Rad end) 43 Deg C
Temp sender boss 86 Deg C
Water pump to thermstat pipe 81 Deg C
Water pump to Valley pipe 77 Deg C
Water pump casing (top) 65 Deg C

Wow, I've gone on but I hope I've covered everything and I HOPE this is a simple case of some special bleeding process. HELP!!!

doesnt appear to be running very hot

jamesmartin said:

doesnt appear to be running very hot

Click to expand...

That was after a brisk and fairly heavy footed drive home, all the proper noises engaged, proper smile mode.

The only other related part that hasn't been changed is the water pump. Well not by me but it is newish. The seller said it was recently replaced.
I'm wondering if its that at fault, not flowing enough.
It's that or an air lock somewhere.

id expect it to get hot if circulation was poor,you dont seem to have any

jamesmartin said:

doesnt appear to be running very hot

Click to expand...

Just an isolated air lock in the area where the sensor is then, which is also partially blocking collant to the heater matrix?

parptoot said:

Just an isolated air lock in the area where the sensor is then, which is also partially blocking collant to the heater matrix?

Click to expand...

that would cause gauge to run cool,have you got the correct voltage to the sender

There's only the one wire and I assumed that went to the guage only, no?

parptoot said:

There's only the one wire and I assumed that went to the guage only, no?

Click to expand...

? wiring and voltage is worth checking

jamesmartin said:

? wiring and voltage is worth checking

Click to expand...

I know the supply and ground to the guage are ok becuase they are shared with the fuel and ummm...the other guage in the row of 3. They also share a ground so it can only be the signal wire then.
The signal ground will be the sensor screwed into the metal of the engine so it's back to that signal wire, right?
I might transfer to another thread if this is more of an electrical issue. Hmmm....

parptoot said:

I know the supply and ground to the guage are ok becuase they are shared with the fuel and ummm...the other guage in the row of 3. They also share a ground so it can only be the signal wire then.
The signal ground will be the sensor screwed into the metal of the engine so it's back to that signal wire, right?
I might transfer to another thread if this is more of an electrical issue. Hmmm....

Click to expand...

just trying to see why it reads hot but engine appears not,where is the sender

The sender is in the front of the inlet manifold, right next to the thermostat housing.

Are you sure it's the right gauge for the sender?
If you had an airlock it would boil unless it was in the cabin heater matrix
Is the viscous fan working properly?

kermit_rr said:

Are you sure it's the right gauge for the sender?
If you had an airlock it would boil unless it was in the cabin heater matrix
Is the viscous fan working properly?

Click to expand...

I'm more sure of the guage than the sender, I think. The guage was bought very recently and I gave them all the details of the car. I'm now wondering if the sender is the wrong part, ah I don't know. I thought it was only the water pump that might not now be right.

I'm sure there are some tests I can do to check signal voltage or summink.

The fan, well it turns with the engine but it's not over heating, only indicating an over heat. Am I missing something?

You should be able to test the resistance of the sender but that's only useful if you know what the gauge expects.
If the fan is engaged all the time, ie it roars when you rev the engine, then that could be why some of your measurements are a bit on the low side
To check the sender is doing what it should, you can hear it up in a pan, the resistance should change smoothly across a reasonable range, i forget the usual numbers

Well that all makes sense. I just need to find what it's sendint and what the guage is expecting.

I still have the issue that the heater isn't blowing hot and that nagging air pocket possibility.

That could well be an airlock. Or a blockage!
When i put mine neck together a couple of weeks ago, i found some bath sealer clogging a small pipe! Caused no end of issues.
Have you flushed the heater matrix? Does it have a good flow?

I stuck the garden hose into both ends and let it run clean so all the coolant was out. Good flow? hmmm, it came out but not at the same rate. I put that down to the make up of a rad,matrix with all its little waterways.
I did the same with the main rad too.

You can always disconnect the heater and use a bit of hose to connect the engine feeds. If the hose gets hot then you know you've got flow and it's either the pipes to or from the matrix, or the matrix itself

Probably your heater matrix is blocked, hence no heat. Maybe go for a different gauge set up? I'd be inclined to say you have a mismatch of sender/gauge.
I believe these are pretty good https://www.ebay.co.uk/itm/Durite-1...562607&hash=item4b33e5ddfd:g:2hUAAOSw7OVak98W