Checking Refurbished water temp gauge

[collins_dan]

How can I check if my recently refurbished water temp gauge is telling the truth? I have a digital reading gun and it indicates the temp of hoses and radiator much lower than gauge is indicating. What temp should various points on the head read: where gauge goes in, above header, on carb side...? Head reads 250F above header, head on carb side 200F, gauge reads 230F as does head where connected, radiator and hoses coming out 190F, radiator and hoses going in 150F. Thanks. Dan

[StressCraxx]

How can I check if my recently refurbished water temp gauge is telling the truth? I have a digital reading gun and it indicates the temp of hoses and radiator much lower than gauge is indicating. What temp should various points on the head read: where gauge goes in, above header, on carb side...? Head reads 250F above header, head on carb side 200F, gauge reads 230F as does head where connected, radiator and hoses coming out 190F, radiator and hoses going in 150F. Thanks. Dan

Dan,

Best way to check the gauge is to put the element in a little coffee pot of boiling water. Gauge should be at 212 at sea level, or 205 in Denver.

Are you using an IR pyrometer? They are good instruments but subject to IR interference too, like the header. IR pyromters like black body surfaces, like flat black paint or rubber (known emissivity). Pyrometers cam have error from shiny surfaces or reflections too.

Regards,
Dan Wise

[collins_dan]

Some other information, no indication of head gasket issue - no low of coolant, coolant looks clean. The advance is 14 degrees. I've tried less advance, but it runs terrible. Carbs are strombergs and cams are L2s. How would I know if the head is bad? I've read some posts about a head getting porous with age and persistent hot running. Thanks, Dan

[GrUmPyBoDgEr]

Beg, steal or borrow a laboratory Mercury or alcohol filled thermometer.
Put that into a container of hot or boiling water along with the sender unit of the temperature gauge & do a direct comparison
That should give you an idea of the accuracy of the unit.
Don't forget that all electronic or electro/mechanical temperature measuring equipment have manufacturing tolerances.
On modern kit expect tolerances of about +3 to -3?C

As a "Modern Dev' engineer", I always had one of those thermometers tucked away in a drawer; just in case.
Never trust modern gizmo's too much.

Cheers
John

[oldelanman]

Best way to check the gauge is to put the element in a little coffee pot of boiling water.

Put that into a container of hot or boiling water along with the sender unit of the temperature gauge

That's exactly what I would have done.....until I got my gauge back from repair. It came with a label saying "kettle testing can cause damage to the gauge" - anyone know why that might be ? Seems to me the gauge wouldn't know the difference.

Regards,

[GrUmPyBoDgEr]

Best way to check the gauge is to put the element in a little coffee pot of boiling water.

Put that into a container of hot or boiling water along with the sender unit of the temperature gauge

That's exactly what I would have done.....until I got my gauge back from repair. It came with a label saying "kettle testing can cause damage to the gauge" - anyone know why that might be ? Seems to me the gauge wouldn't know the difference.

Refurbished oil and water gauge 002a.JPG

Regards,

Bluntly put, I think they're talking bollox.

Coolant temperatures in some cars under certain circumstances can exceed 130?C.
Boiling water in a pan never exceeds 100?C

John

[billwill]

Call the firm that did the repair and ask them exactly what that notice means.

[oldelanman]

Call the firm that did the repair and ask them exactly what that notice means.

Just sent them an e-mail............

[Tonyw]

Dan,

Your temp bulb is in the actual water stream and is as close to the heat as is possible, using an infra red thermometer you are measuring the outside temp which has to be less than inside, the temps you mention for various parts of the engine sound about right to me.

I would trust the infrared thermometer over the temp gauge any day though. A useful test is to measure the bottom and top hose temps as this will show you how efficient your radiator is.

Generally a blown head head gasket will allow combustion pressures to enter the coolant stream and because combustion pressures are higher than radiator pressures this will displace coolant and push it out into your overflow bottle, it may also allow water into the cylinder on switching the engine off.

Tonyw

[andyelan]

Hi There

I assume the repairers might be concerned that the bulb of the instrument could come into contact with the electric element of the kettle.

Andy

[GrUmPyBoDgEr]

Hi There

I assume the repairers might be concerned that the bulb of the instrument could come into contact with the electric element of the kettle.

Andy

You've lost me there Andy; what would happen if it did?
John

[billwill]

>it may also allow water into the cylinder on switching the engine off.

It also sucks water into the cylinder on the inlet stroke, as I have found to my cost, not just when you switch off, especially as the water chamber has been pressurised by the combustion stroke.

[andyelan]

Hi John

Without any water a kettle element will run a lot hotter than 100 degrees C.

If the instrument bulb were to make direct contact with the heater element in the kettle then that part of the bulb would not have the insulating effect of the water and so could be subjected to the full metal temperature of the element, that could possibly damage the instrument (and maybe also the kettle). I agree chances of it happening are slim but maybe that is what the repairers are covering themselves against. The same thing could also happen if the bulb were to be placed in a pan of water on a stove and it were allowed to touch the bottom.

Andy

[collins_dan]

If the temps from the infrared are right, then why would the coolant temperature and the carb side of the head be much lower temp than the header side. Is this any indication of exhaust gases temp being really high and heating up this side of the head? The frustrating thing is that the car is running great. Thanks, Dan

[bill308]

As a follow up to StressCraxx, assuming the IR istrrument is working properly, the surface temperature it sees depends on the surface's emissivity. A perfect black body will have an emissivity of 1.0. The FLIR folks make instruments for the military and one of their tricks is modify the target surface emissivity with a spray coating of Desenex foot powder or use a patch of electrical tape. These surfaces will yield an emissivity of 0.9 or better. Some paints will get you into the 0.8-0.9 range. Color generally only affects light in the visible spectrum, with minimal affect on the IR spectrum the instrument sees.

The hose and radiator paint probably have emissivities in the 0.8-0.9 range, so their temperatures will probably be pretty accurate. Metals on the other hand have much lower emissivities with corresponding lower apparent temperatures, especially if shiney.

The bottom line is the actual temperature of the target will be a little hotter than what an IR instrument sees unless it has a built in emissivity adjustment and you know what to set it at.

Bill