I was told that the stock gauges have a tendency to be less then actuate. Plus I am not happy with the C to H read out. So I was wondering the best place to put the sensor.

 

Put the sensor for your new, more accurate (presumably) gauge in the same spot as the stock sensor.
The stock sensor (and the hole, obviously) is some bizarre British pipe thread- 1/8 x 28, IIRC- and most aftermarket sensors are standard pipe thread- 1/8 x 27.
I haven't had a problem with the 1 thread per inch discrepancy and consider them interchangeable.
Others may disagree.

 

I installed mine on the backside of the waterpump housing.

 

if you dont mind the work involved, the best place for a water temp sensor is behind the waterpump housing below the thermostat.
You would have to take the waterpump housing off, drill a hole, tap with appropiate thread and install the sensor.

 

the old megan racing ones use to fit in the s5 blocks stock location.

 

I wasn't going to remove the stock one.

 

on s4/5 engines, front plate , cas side,, 1/3 up from sump is a pipe bung into the coolant galleries

you can replace this with a bush suit your new sender or you can tap the pipe bung to suit

 

the only problem is my lack of time to get said gauge i am going to be home for a few days. not long enough to order one off line. so i may have to pick one up from the local parts store.

 

If you are really concerned about cooling buy two coolant gauges and sensors and put one before the radiator and one after it. Then you can tell if something like changing the air path to the radiator or the radiator itself make a difference. 210F is a good temperature to maintain.

 

take out the stock one and put the new one in there drill and tap if necessary

 

How ironic, I was about to start my own thread asking advice between the best of two places on my radiator. I already have the front of my water pump housing tapped for either temp gauge or electric fans switch.



I need a second spot so that I have both temp gauge and electric fan control....and don't want to loose my OEM gauge. Redundancy is safest.

I have a Koyo radiator and just today I found that my drain plug and air bleed are very close to matching my gauge sensor. My question is which spot on the radiator would be best. I'm guessing air bleed because that's the point it will be the hottest.

 

That works. What thread pitch and diameter is the air bleed and sensor? "Very close" isn't something you should be thinking...

 

Very true. I believe it's the difference in the two common thread measurements....um...NPT and BSPT (IIRC). My gauge sensor/sender is 1/8" NPT and will start to thread in perfectly. But about 1/2 to 2/3 of the way in it catches. I haven't forced it and won't do anything till I decide what direction to take with my fan control.

I have my waterpump housing tapped for the gauge sensor/sender.

I have to decide between the Volvo two speed setup or do a single speed control. If I do a single speed I'll use a Summit Racing 3/8" NPT switch.

 

i read that the sunpro gauges aren't very trust worthy. what gauge brand would you recommend?

 

Go with a pro-sport. They match the stock gauges pretty well, and are pretty nice for the price.

 

He said he wouldn't be able to order offline, I would go with Autometer from your local auto parts store.

 

well if i can get them in a few days i will order on line. preffer place to order them?

 

i saw they have a radiator hose adapter for pro sport. is that worth getting? i guess it won't give a good reading unless the thermostat is open.

 

Its hard to see but if you are using a n/a engine tee the sensor into the thermowax? (i forgot) coolant line with some fittings (cost of fittings was under $6) The sensor is roughly in the middle against the firewall in my picture.
This was absolutely the quickest and easiest way to me to do this. I am using a prosport temp gauge, and im pleased with it.

 

You answered your own question. I decided against it because you wont realize your thermostat failed till its to late.

 

I the main reason i want to add this gauge is too make sure i don't have a coolant leak on my trip back to FL. i am told that i my have a coolant leak, however the tech was unable to find it. my coolant was low. but i think it was because i didn't bleed the system correctly. i firgued the gauge will help me out. because my stock seems to read colder then it should. about 1/4 cold i think. pro gauge has adapter for the 1/8 BSP.

 

The stock gauge is accurate enough to tell you when you're so low on coolant your engine is at risk. Plus...there should be a "low coolant level" sensor that will turn on a dash light when the coolant is low. It's on top the radiator and has two wires coming from it. I'd keep a gallon of distilled water in the car until you find the leak or are sure there isn't one.