Temperature Gauge Over Reading?
Temperature Gauge Over Reading?
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Discussion

mattgtd

Original Poster:

322 posts

166 months

Friday 5th June 2015
quotequote all
Car is running absolutely spot on at the moment, but the temperature gauge is slightly suspect lately.
The fans are all cutting in and out spot on and it all seems sweet in the cooling department, but I've noticed that the gauge is sitting around the 85 / 90 and then going up to 95 / 100 ish sometimes. It does come back down, but takes a moment.
I don't actually think the car is hot, but just think it's the gauge miss reading.
Is this just a simple new sender job, or more to it maybe?
If it is a new sender, does the distributor need removing? - Job for Dom and the boys if so, I'm not getting involved with timing!

Cheers guys.

mattgtd

Original Poster:

322 posts

166 months

Sunday 7th June 2015
quotequote all
Nobody? Any ideas would be appreciated, car was doing it again yesterday but really is running spot on.
Cheer guys.

NZ fan

312 posts

163 months

Sunday 7th June 2015
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It's no secret the temp gauge is a rough indication of actual temp at best. If you have access to rovergauge it will show you a much more accurate reading of the coolant temp. My fans cut in at 96deg. On rovergauge. Remember boiling point is not 100deg. Because the system is inder pressure which raises the boiling point. From memory about 1deg. Per 2psi so if the system is under 12psi the boiling point will be around 106deg.

Ozstyle

392 posts

252 months

Sunday 7th June 2015
quotequote all
Hi,

assuming readings are true, fluctuating water temperature can mean air trapped in the inlet manifold (near temp sender), possibly a faulty thermostat or faulty pressure cap. Worth fully bleeding the cooling system, check for any possible leaks where air maybe getting into the cooling system. Thermostat change and pressure cap worth doing if history not known and if they make no difference at least you have some useful spares.

Ozystle

J400GED

1,202 posts

266 months

Sunday 7th June 2015
quotequote all
mattgtd said:
Car is running absolutely spot on at the moment, but the temperature gauge is slightly suspect lately.
The fans are all cutting in and out spot on and it all seems sweet in the cooling department, but I've noticed that the gauge is sitting around the 85 / 90 and then going up to 95 / 100 ish sometimes. It does come back down, but takes a moment.
I don't actually think the car is hot, but just think it's the gauge miss reading.
Is this just a simple new sender job, or more to it maybe?
If it is a new sender, does the distributor need removing? - Job for Dom and the boys if so, I'm not getting involved with timing!

Cheers guys.
Does it sit at 85/90 when driving and then go to 95/100 when stationary for a while then come down from there whilst still stationary?

anonymous-user

83 months

Sunday 7th June 2015
quotequote all
Mine goes all over the place, was up around 60 today (whilst warming up on a short drive), then dropped to 50 when driving around, then as I slowed down to walking pace it shot back up to 70 in about 3 seconds!

When my Radiator was replaced by Leven, they noticed the weirdness of it suddenly dropping right down then coming back up again.

It has been like it for years, even before the new rad and hoses.

I have just put it down to an electrical gremlin somewhere wink

Edited by anonymous-user on Sunday 7th June 19:20

mattgtd

Original Poster:

322 posts

166 months

Tuesday 9th June 2015
quotequote all
J400GED said:
Does it sit at 85/90 when driving and then go to 95/100 when stationary for a while then come down from there whilst still stationary?
It does this but it takes ages to come back down from the higher temp when stationary with fans running. I've checked and both fans are running on and off perfectly.
I'll try and get somebody close to me with rover gauge to have a look.
My suspicion is that the car is actually running fine with the cooling system doing it's bit, but just the gauge is a bit all over the place - would just be nice to confirm and put mind at ease as you'll all understand.
Cheers.

Englishman

2,253 posts

239 months

Tuesday 9th June 2015
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I have the opposite (on my Griff), an under reading gauge compared with Rover Gauge!

It usually sits around 50C in cold weather rising to about 75C when the fans cut in. Changing the sender made no difference. Thinking about finding another gauge but maybe that'd be just as bad.


Smokey Boyer

509 posts

160 months

Tuesday 9th June 2015
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My gauge had similar issues, and was reading about 12 degrees cold compared to the ECU sender reading in TunerStudio (via Megasquirt ECU). The wire from the sender had a 20 ohm resistor in it very close to the sender. Changing the resistor is relatively easy if you can use a soldering iron. I am still experimenting with different value resistors and currently have a 10 ohm resistor in with has got the dash gauge to within a couple of degrees of the ECU gauge.

Englishman

2,253 posts

239 months

Saturday 20th June 2015
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Just checked and no resistor in the lead from the sender on my car so looks like the gauge.

I've managed to find another temperature gauge with a black face to try and confirm when I get time to remove the dash, but I will carry on looking for one with a magnolia face. If anyone has a spare they don't want please pm me.

Otherwise I may try to change over the mechanisms, but seems the front of the gauge is bonded or glued on so doesn't look easy. Does anyone know of anyone that repairs them?

Ozstyle

392 posts

252 months

Sunday 21st June 2015
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TVR sometimes fitted a resistor at the back of the gauge to drop the temperature reading. I found a 10 ohm on the back of my gauge in the wiring, dropped the reading at operating temperature by 10 degrees