ThermoCap radiator cap gauge

I know that some of you are running this radiator cap temperature gauge since SheWolf introduced it to us. They're made or distributed by Mr. Gasket and sold in speed shops like Jegs. I'm a nut for gauges (don't look in my diesel truck), so a real coolant temp gauge, especially one this easy, seems like a must-have.

So I put it on for the first time this morning and rode to work. 85ºF ambient temp, average speed of 45 mph, ride time 30 minutes. This is a pretty low-stress condition for the motor, but the ThermoCap gauge registered a constant 240º F. My coolant is new, full, not leaking, not boiling, and the cap in on tight. I really don't think it was 240º. So I guess tonight's fun will be to put a pot of water on the stove and break out all my thermometers to see who's telling the truth, or at least a majority opinion.

Any of you ThemmoCap users ever check your gauge's accuracy? I could live with it being off, much like my speedometer, but starting in the red might be more than I can bear.

So much for being easy

Yours was in the red? I've never had mine actually go there.

Oooh... this is neat! Ok, on the TODO list now

I tested this and it's way off. Boiled a pan of water, got 3 stick thermometers, put them all in the water. The 3 stick thermometers registered about 200ºF while the ThermoCap gauge read 250º. I'm into this thing for $38 now, more if I send it back (to Jegs) for a replacement. Is there any reason to think a replacement will be any better?

Boondocker wrote:

I tested this and it's way off. Boiled a pan of water, got 3 stick thermometers, put them all in the water. The 3 stick thermometers registered about 200ºF while the ThermoCap gauge read 250º. I'm into this thing for $38 now, more if I send it back (to Jegs) for a replacement. Is there any reason to think a replacement will be any better?

I don't know much about them, but I wouldn't bet my life it will be different. Did it come with a confidence interval for the gauge (i.e. +/- 10 degrees)?

I cast bullets and then harden the lead by heat treating in an oven afterwards - wheelweight is cheap, and linotype is getting to be more costly per pound than nice fresh lobster just off the boat. That requires reasonably exact thermometers. I spent some dough on the garden variety ones available for casting and found as you're experiencing that their relationship to true temperature was widely variable - and the error wasn't even consistent. So eventually, I broke down and invested in Temperil sticks and a laboratory grade thermometer. Maybe there's radiator cap gauges with a guaranteed accuracy range.

If the manufacturer guarantees an temperature error range you can live with, return it. Otherwise, if you have to have it, maybe you can calibrate it to your "Uh oh" temperature using your thermometers and a liquid with a higher boiling point like pure ethylene glycol (boils somewhere around 275 F, I think).

Jäger wrote:

I don't know much about them, but I wouldn't bet my life it will be different. Did it come with a confidence interval for the gauge (i.e. +/- 10 degrees)?

If the manufacturer guarantees an temperature error range you can live with, return it. Otherwise, if you have to have it, maybe you can calibrate it to your "Uh oh" temperature using your thermometers and a liquid with a higher boiling point like pure ethylene glycol (boils somewhere around 275 F, I think).

It comes in different cap colors, but no accuracy range. With my luck, if I ship it back, it'll just end up costing me more for the same thing, or I could get a refund on the unit price and pay shipping and handling for naught.

I made another pass at calibration and used a Sharpie to mark the "OK" line. About 240 on the cap is around 185 to the stick thermometers. It's actually pretty close at ambient temperature, like 90ºF, which is almost useful for indicating the temp of my garage in the morning.

I just installed these caps on mine and my dad's WRRs... We are going on a ride next week so we'll see how well they do.

Mine was crap. After a few hundred miles, the cap started leaking about 1/3rd of the way into a 400 mile round trip. I replaced it with the radiator cap off a Kia Sorrento (perfect fit!) and never looked back.

My Cap works great, they can work correctly. I like the matching blue. My cap got to about 240 degrees on a 100 degree day in rush hour traffic, and thats when my fan clicked on, and the temp went down to 200 degrees. Just wanted you to know that they can work. Mine is more than a year old, its on an 08 WRX (from Jegs)

Hello, can you tell me what kind off ThermoCap you have, Garman? I think that the 110 Kpa (16 psi) SMALL - Part No: 1405 model, will be work in our WR250R, but I don't know anyone in Spain with a one.

Thank you

Well that's the thing with gauges - you rode your bike for a long time worry free, then you put that gauge in and you keep looking at it and start worrying. Been there done that - no gauge for me

Interesting... have you tried?

WRXR wrote:

Well that's the thing with gauges - you rode your bike for a long time worry free, then you put that gauge in and you keep looking at it and start worrying. Been there done that - no gauge for me

Yep, sometimes ignorance is bliss. Add a gauge cap, and you look at it and worry about the temp each mile. No cap for me. I already start to worry when I hear the fan and my right calf starts getting warm.

M1A Rifleman wrote:

WRXR wrote:

Well that's the thing with gauges - you rode your bike for a long time worry free, then you put that gauge in and you keep looking at it and start worrying. Been there done that - no gauge for me

Yep, sometimes ignorance is bliss. Add a gauge cap, and you look at it and worry about the temp each mile. No cap for me. I already start to worry when I hear the fan and my right calf starts getting warm.

Hahaha....hear a different noise/sound from the bike is even worse. Then that's all you can think about.