Water Temperature Gauge Installation on SAAB c900

You may recall a couple weeks ago I got the oil pressure gauge connected, and now it's time to get the water temperature gauge going.  I've planned it out in my head and now I get to actually do it.

Like the oil pressure gauge, the water temp is also mechanical.  Which means we have to tap into the cooling system somewhere close to the engine block and put the sensor there.

I bought a new heater hose and the Autometer heater hose adaptor.

I could have used my old hose, but I figured if I goofed up the installation, I could just reinstall the old hose if needed.

You can see the new hose above, along with the adaptor.  You could also replace your factory sensor with the one for an Autometer gauge, but the sensor on a c900 is at the front of the block near the thermostat housing, and the cable (actually it's a capillary tube) for the sensor is sealed - it contains a liquid - and it won't reach that far. Hence Plan B, hack into a water hose.

You will note that the hose is a bit curved and the adaptor is straight.  I have a plan which I believe will allow this to work.

I had marked the ends of the hose with the approximate locations of the existing fittings on the car the hose connects to.

Then I just cut the hose with a razor saw.

The hose is a tight fit onto the adaptor, so I boiled the hose - now cut into 2 pieces - in my hot pot/hide glue heating device.

Best $12 I ever spent.

Hopefully the hose will expand due to the heat and will slip over the adaptor ends easier.

Hopefully.

We take our cooked hose out of the water.

At this point it looks like a sausage.  Or more accurately, it sort of resembles the famous Swedish sausage called värmlandskorv. Värmlandskorv is a wonderful sausage made of beef, pork and potatoes.

Maybe we should refer to this sausage as "Värmareslangkorv,"which would mean in English, if the Bing Translator is correct, "heater hose sausage."

I bet it would be pretty rubbery if you tried to eat it.

So the two hose ends went over the adaptor ends - nice and tight.  I don't think it will leak.  Especially when it has clamps on it.

Now to see if this assembly will actually fit in the car.

You can see our korv - er...hose on the left.

The factory hose is directly to the right.


This has been too easy so far.  I expected this to be fraught with problems, I don't know why.

This is the part I've been dreading.  Removing the old hose and seeing a liter of coolant go everywhere.  I have no idea how much coolant is in there, but I put a small bucket under the hose to catch whatever comes out.

That's it!?  Wow.  That wasn't too bad.

Side story: many years ago I was helping someone take an oil cooler out of an early 70s MGB parts car (to put in my 1967 MGB).  He cut the heater hose for some reason and when the (old, dirty green) coolant came out he said, "hey, it's bleeding British Racing Green!"

Guess you had to be there.

Then we undo the clamp at the other end of the hose - the joint between the hose and the external water pipe off the engine block.

I couldn't get the bucket under the fitting, so I just stuffed a rag into it.  There was a bit more coolant that leaked out, but still not a lot.

Now a test fit.

It may not look like it lines up, but I trimmed a bit off the end nearest the camera, and it worked great.

The "T" joint the hose connects to at this end has enough flex in it due to the other hoses connected there on the other sides that I have plenty of room to maneuver the hose and the fitting to get them to mate.

Here it is.  It works perfectly.

Note I put the clamps back on and put clamps onto the hose where it meets the adaptor.  Snugged them up and all looks good at this point.

Put some thread sealer on the big fitting which goes into the adapter...

...and tighten it up.

This is the actual temperature sensor and its fitting going into the brass fitting we just put on.

This whole line is sealed - it's sealed at this end where the sensor is, and it's also sealed at the gauge end.  It's actually a capillary tube that contains a temperature-sensitive liquid that controls the movement of the gauge needle with changes in temperature.

Here's the adaptor, hose and sensor all installed.

Now that I see this picture, I realize I could have turned the adaptor to the right and run the capillary tube under that A/C hose.  I can always change that later.  On second thought, those fitting nuts might be hard to access.  Hmmmm.

Incidentally, the engine was running in this shot - note there are no leaks. Yes!

Moment of truth inside the car.

With the engine getting up to normal temp, still no leaks, and now we have a calibrated water temp gauge!

And to think I envisioned coolant everywhere.  This went very easily indeed.

The factory water temp gauge is still connected, so I now have 2 working gauges - I guess redundancy is a good thing. The factory gauge is uncalibrated - it just reads "L" to "H," so it's nice to know the exact coolant temperature.