1979 245 Coolant Gauge

[spease1984]

Hello knowledgeable peeps,

My coolant gauge read above half way when I got my 245.

It had a fixed fan which seemed pretty pathetic.

It now has a larger radiator out of a 740 with electric fan and 2 speed controller from another Volvo and a sender unit from a BMW with the adaptor thing put halfway in between the top coolant hose.

However.... the gauge still gets to just above 3/4 before the electric fan kicks in and sometimes the 2nd speed kicks in first before dropping down to the lower speed.

The car doesn't feel like it runs hot but the other day it got into the red zone so I pulled over and the bottom hose was quite hot.

I swapped the fan sender unit for one that kicks in earlier but this didn't work at all (assumed I got a duff sender) but my brain says if I have a 87oc degree thermostat how can a sender unit which is meant to open at 80oc degree work as the coolant won't be flowing!

I've changed all the hoses, water pump, thermostat sender, unit and coolant expansion cap but now I'm out of ideas.

Could it just be that my early style instruments just are reading too high??

I really don't want to blow my head gasket or worse warp my cylinder head.

Any ideas??

Thanks

[Clifford Pope]

Originally Posted by spease1984

I've changed all the hoses, water pump, thermostat sender,

Is that the instrument sender or the one controlling the electric fan?

[Clan]

Originally Posted by spease1984

Hello knowledgeable peeps,

My coolant gauge read above half way when I got my 245.

It had a fixed fan which seemed pretty pathetic.

It now has a larger radiator out of a 740 with electric fan and 2 speed controller from another Volvo and a sender unit from a BMW with the adaptor thing put halfway in between the top coolant hose.

However.... the gauge still gets to just above 3/4 before the electric fan kicks in and sometimes the 2nd speed kicks in first before dropping down to the lower speed.

The car doesn't feel like it runs hot but the other day it got into the red zone so I pulled over and the bottom hose was quite hot.

I swapped the fan sender unit for one that kicks in earlier but this didn't work at all (assumed I got a duff sender) but my brain says if I have a 87oc degree thermostat how can a sender unit which is meant to open at 80oc degree work as the coolant won't be flowing!

I've changed all the hoses, water pump, thermostat sender, unit and coolant expansion cap but now I'm out of ideas.

Could it just be that my early style instruments just are reading too high??

I really don't want to blow my head gasket or worse warp my cylinder head.

Any ideas??

Thanks

The standard 245 cooling system has vast reserves of cooling capacity , all that work you have done is unnecessary , I would put it all back to standard and start again , there is an instrument voltage regulator behind the instrument panel but if the temp gauge was reading high so would the fuel gauge .. have you noticed that?

[spease1984]

Thanks, it was the sender unit in the cylinder head that I replaced.

I can't say I've noticed the fuel gauge reading high but then I haven't driven it that much and I had all the issues where someone thought it would be a good idea to put twin 45 on it.

Now it has a single 32/36 DGAV it drives soo much better but like I say I haven't done that many miles in it.

I'm certainly not putting the cooling system back to standard after the amount of money I spent on it.

I always put electric fans on all of my cars so I feel more comfortable in the summer traffic.

I just want to know it's running at the right temperature even if the gauge is wrong.

I thought there must be some kind of voltage regulator on the speedo but can't find any mention of it online.

[Paul240480]

The OE viscous system was brill. Yeh if going up lots of steep inclines, the guage would raise a tad, but that’s normal.

[spease1984]

Was looking at fitting a viscous but an electric fan came up at a decent price and then it also meant I could fit a bigger rad and seeing as I have a K&N filter I didn't need the space for the orginal air filter system so thought I'd go for that.

Thinking I may fit another temperature gauge now.

[Clifford Pope]

Before making any more changes I would take steps to calibrate the existing gauge/sender.
If you remove the sender, extend the wire and also earth the body of the sender, you can pop it in a pan of boiling water and follow its temperature as it cools by comparison with an ordinary mercury thermometer.

That way you will know the exact engine temperature at each position on the gauge, and can judge whether it needs replacing.


PS. I too once was very keen on electric fans. I have since learned the truth that the viscous fan works excellently. If you have an electric fan you need to check it very frequently to see that it is still running and not jammed with leaves or insects. Ask me how I discovered that !

[Clan]

Originally Posted by Clifford Pope

Before making any more changes I would take steps to calibrate the existing gauge/sender.
If you remove the sender, extend the wire and also earth the body of the sender, you can pop it in a pan of boiling water and follow its temperature as it cools by comparison with an ordinary mercury thermometer.

That way you will know the exact engine temperature at each position on the gauge, and can judge whether it needs replacing.


PS. I too once was very keen on electric fans. I have since learned the truth that the viscous fan works excellently. If you have an electric fan you need to check it very frequently to see that it is still running and not jammed with leaves or insects. Ask me how I discovered that !

indeed , and as i said above the standard system with the standard fan and cowl ( I Hope the cowl isn't missing otherwise the mechanical fan is useless . ) Is extremely competent at keeping the gauge in the central position in all conditions .. I would check the instrument voltage regulator , it should show an average of 10 volts . ( it pulses unless it has been replaced by the later electronic one ) so best use an analogue voltmeter with a needle ..

[spease1984]

Turns out the gauge just simply reads about a quarter too high.

I also had a bad relay which was preventing the electric fan from coming on properly.

All sorted now I just have to 'live with' a gauge that over reads.
Suppose that means the fuel gauge does too, so will be keeping a Jerry can in the boot.

Thank you for all your replies.

[Clan]

Originally Posted by spease1984

Turns out the gauge just simply reads about a quarter too high.

I also had a bad relay which was preventing the electric fan from coming on properly.

All sorted now I just have to 'live with' a gauge that over reads.
Suppose that means the fuel gauge does too, so will be keeping a Jerry can in the boot.

Thank you for all your replies.

Have you got an average of 10 volts supplying the fuel and temp gauges? The gauge is adjustable inside , someone may have tampered with it .. It is pretty simple to replace the volvtage regulator if you believe the fuel gauge is also over reading , you will not need to adjust the temp gauge then ..