Hey, I've got an 88, with an S5 block. Prior to the swap, it would run all the way up to "H" (bad motor, which consistantly overheated). After the swap, it won't get any hotter than about an 8th up the stock gauge. I have:

A) replaced the gauge itself from a different cluster
B) removed the temp sensor, under the oil filter, & lightly sanded the copper probe so it's not copper oxidation impeding readings

Car has a Mazda OEM thermostat, ALL stock shrouding (fan shroud, belly pan, both plastics that go in front of the rad), & a stock clutch fan.)

Thanks for the help!

 

I don't know if this helps... but mine is the same. Normal for me is 1/8th. When it's 100+ outside, I see 1/2 maybe...

 

1/8 of the gauge is right at the lower end of operating temperature.

I have compared the factory S4 gauge to readings from a brand new water temp sensor (2 wire on the back of the water pump housing) read through a standalone. With the needle 1/8 of the way up water temps are usually right at about 180F which is where the thermostat cracks open. Now, different ambient temperatures can have a bit of an effect on what actual temperature the needle corresponds to. But I'd say in my experience 95% of the time if the s4 factory gauge is 1/8 of the way up the thermostat has begun to open.

 

Thats where mine runs at.

 

That's where mine ran prior to blow ing it. Although I was running a crazy good e fan and never seen hotter than 1/4 the way up with ac on and really beating on it.

 

You should be fine, but without anything more accurate you're guessing. The gauge readings can vary so if you want to be certain about it, think about installing an aftermarket water temp gauge.

 

The gauges and senders are getting pretty old, so everything probably is fine. However it is woth checking the thermostat. Just start the car cold and feel the upper rad hose. It should not be hot for quite a while, well after the engine block and water pump housing is hot. If that's the case, the thermostat is probably fine. Or take it out and boil it in a pot of water.

 

s4 temp gauge usually run 1/8 or 1/4 at norm running temps

 

Excellent info-- Thanks guys, you've eased my worries =)

For whatever it's worth, I've also taken the wire off of the sending unit, and grounded it to the block, and the gauge shoots up to H, in about 10 seconds, thus proving the gauge isn't "stuck".

Thanks again!

Landon

 

mine has me worried. on the s4 there are the 3 lines at the bottom, two lines that are horizonal and then a 3rd one that is slightly angled at the "low" temp range. well when cold it sits at the lowest one. at "full" temperature it sits between the 2nd and 3rd one. it does not even go up into the whole space of the needle. at first i thought my gauge was broken but then noticed it moves VERRRRRY little!!.

on a cold morning it normally wont heat up to temp by the time i get to work, and in afternoons it gets right up to temperature. do i not have a thermostat? or did the previous owner put in one of the stant crap ones? keep this in mind. previous owner had the idle super far off to where it wouldnt hold an idle, the lug nuts were tightened over 200lb ft and hadn't had new spark plugs since he had it rebuilt...

 

Is it normal for s5 to run 1/2 on the temp gauge mine ran there for about a year everyday with no problems..

 

Thats what happens when a super high quality rebuild is being cooled by a fully functional stock cooling system w/ all the appropriate ducting. I love FC's we're so used to **** going wrong, that when it goes right we get concerned

 

^lol.

my s4 NA has run 1/2 way at operating temp since I got it. no problems,starts fine, never over heats.it starts fine in the winter too (had to drive it for a month last winter when I crashed my subie). I drift it a bit and took it to a drift event where I was running 50+mph past 7k redline 50% of the time over 6 hours and temp was fine (had the heat full up and blasting too). I'm guessing its normal for my car. its all stock btw with clutch fan working and all shrouds. 134k odometer. almost forget, my 5th/6th ports aren't working though. my split air pipe is missing since I got it.

 

OK....S5s are supposed to sit at 1/2 on the gauge, but the gauge on an S5 is non-linear. It has three positions: "cold", "normal" and "new engine".

The S4 gauges are far more linear. Normal operating temperature for an S4 is 1/4 on the gauge which is about 86 degrees. Halfway up is about 88 degrees, and 3/4 is just over 90. Pegged, it's about 100 degrees.

 

Oh ok, I figured but wasn't sure. Thanks

 

Interesting. This shows variation in the OEM gauges. 1/4 of the way up is about 90-95C for me. 1/4 way up is about 100C. I've only run over 100C one time, except maybe at a hot start, so I can't tell you where it pegs exactly.

 

You don't happen to have an S5 temp sensor connected to the S4 gauge cluster do you? My engine in my S4 TII has S5 irons (and an S5 sensor since the holes are different sizes between the 2 series'). I have an aftermarket temp gauge now, but when I had it hooked up to the S4 cluster, the temp would sit at the 1/8 mark or so, lower than any S4 I've seen.

 

My 88 vert runs at 1/4, while my 88 gxl runs at 1/2. Seems weird.

 

And I think you just answered my question! Yup, it's a full S5 block, so the temp sender is S5 as well.

I'll have to get an aftermarket gauge to be perfectly sure.. Thanks!

 

lol, landon, that was the very first thing I suggested when u mentioned this issue 2 weeks ago...

 

not true. please delete this post so i don't look as much like an idiot. hahaha