Oil Pressure and Water Temp Gauge ideas (long)

[trpower7]

I am installing an Autometer Oil Pressure and Water temp gauge into my S13, even though I'm not turbo yet I'm an engine statistic fanatic. Both are the electrical gauges, here is my layout for each.

Oil Pressure Gauge: Flanking the gauge cluster mounted on top of the dash to the right. I will be Teeing off the stock oil pressure gauge sender, and converting one side of the T to the 1/8 NPT size that autometer uses. The other side of the T will be the stock dummy light sensor. In the future I can take off the dummy light and use that side of the T for my oil feed line. No real questions here, I think I've got this one down.

Water Temp Sensor: Here it gets a bit hairy. I've explored all the options discussed all over the internet and it boils down to this. I don't want to buy a $90 blitz Upper Rad hose plumbed for the sensor. I don't have the time or equipment to drill and weld my own bung for a 1/8 NPT fitting. I don't trust just drilling a hole and filling it with JB weld and my fitting. So I'm going to try to T-off the coolant temp sensor that feeds to the cabin, and attatching the cabin gauge to one side and the Autometer fitting to the other. Here i have a question. Will the coolant have lost sufficient temperature after it travels the inch of total travel to the sensor? Will I get inaccurate readings with this setup? Has anyone done this before? All input will be appreciated.......

[yellow_jacket]

It probably will not read acurately as the sensor will no longer be in the stream of coolant.

[Nathan]

I would think it would be a bit delayed...but I dont think it would be a BIG deal, you'll still figure out pretty quick if something major goes wrong.

[trpower7]

I think becuase the system is pressurized it will still see the exact same coolant as the stock sensor, not quite sure though......

[yellow_jacket]

It has nothing to do with pressure. The stock sending unit is placed where it is for a reason. It needs to be in the coolant flow to read accurately. A little delay could easily result in severe overheating.

[trpower7]

All the sensor being in teh wrong place doing would result in an incorrect sensor reading, not overheating. The thermostat is mechanically controlled by it's own internal, temperature activated, spring loaded device. The car would not overheat even if all the temp sensors were disconnected, it would just run insanely rich because the computer would be getting bad readings. If you have the capacity amount of coolant in a system, and T off a small section of that system, gravity and water pump output, as well as physics in general, will keep coolant cycling through the entire system. Overheating CANNOT be caused by stock temp sending unit malfunction.

[yellow_jacket]

I didn't say it would cause overheating, I said it would result in overheating. This being true because your gauge reading will be delayed. So while your gauge is reading cool your motor will have actually heated up.

Are you talking about teeing off the temp sending unit or the coolant temp sensor? You have mentioned both. they perform two different functions. If the coolant temp sensor is out of the stream it will cause erronius air/fuel ratios. If the temp sensor is out it will just cause erroneous gauge readings.

As far as the gravity and water pump thing goes yes that is part of physics, but fluid dynamics will tell you that you will have negligable flow to your sensors because it is a blocked off passage and gravity will also be negligable.

When its all said and done, the only way to get a reliable temp. reading is to drill a hole and tap it or buy the adapter to put the sensor on the coolant hose.

[trpower7]

It has nothing to do with pressure. The stock sending unit is placed where it is for a reason. It needs to be in the coolant flow to read accurately. A little delay could easily result in severe overheating.

Once again, the gauge in no way controls the operation of the engine's cooling system. In no way would even a total gauge failure, or the ECU's coolant temp sensor failure, cause the car to overheat. An erroneous gauge reading yes, engine overheating, definetly not. The temp sending unit for the ECU and for the cabin gauge sit right next to each other in all DE engines. If the system is pressurized even if the sensor sits outside of the stream it will still recieve the same coolant at the same temperature that a sensor IN the stream would recieve. Hot coolant flowing out of the head will flow into ANY cooler space due to physics, this includes any area that has been Ted off. In no way will it be blocked off, let me see if I can computer draw this thing........ Autometer l l l l------- l------- l l l l l Stock Gauge

If this T is directly connected to where coolant would flow out of the head it would see just as hot a temperature as a gauge sitting directly in the flow of it, what with this hotter coolant being pulled into every available space both by the water pump, internal system pressure, gravity, and the temperature difference. However, I suppose all this is a mute point as I have developed another sytem which DOES place the sensor in the flow of coolant in the upper radiator hose, I found the solution on an old FD board, but physics and chemical dynamics is always tons o' fun!!!

[Nathan]

What is your new way of doing it? I thought the T was a viable option...not the best but serviceable.

[trpower7]

Yes, I still believe in the T and may even try it since I already bought the fittings. But I am going to get a 3 inch long piece of 1 1/2 steel tube, drill a small hole and tap it for 1/8 NPT. I found a machine shop nearby that said I could use the tap if I bought the guy a beer. I'll then cut the upper radiator hose in half, trim an inch or so off of the middle section, and then reattatch each end to that metal piece, and voila, temp sensor in the hot coolant stream.

[slw240sx]

why not buy a 2$ sensor holder from autozone cut your top rad hose insert the piece and clamp the hose back to each side of the sensor holding pipe that you just buy for 2$ or even make one on your own,, installing a water temp gauge shouldn be this hard man!! its a hour or less job!!

[yellow_jacket]

Once again I think you misunderstood me. Probably because I didn't write it very clear. You could possibly over heat the car NOT because the gauge changed anything. Just because if you had some problem and the car started to over heat the gauge might not tell you until too late, thus resulting in overheating.

As for the flow you are talking about, yes you will have coolant and pressurized coolant touching the sensor constantly. We agree on that. The only thing I disagree with is that you will not have moving coolant in the small space created by the T. The problem is that at the surface of all pipes the velocity of the liquid is zero. So the coolant will basically skip right over the passage, thus creating no flow in that chamber.

As for the argument that the temperature difference will create a flow, that may be true. I honestly am not that strong in that area. So it may create enough of a flow from the temperature differential. Then again, it may not. Outside of the fluid dynamics aspect I am a little unsure. I just don't know that much about chemical engineering. I guess thats why I am an ME.

Glad to hear that you worked another solution out though. I would have been interested to know how this worked out also.

[justjuiceit4]

According to the gauge kit I got, it says that using a T-fitting for coolant will not give you an accurate reading. I was wondering if installing it where the coolant drain plug on the block would be a good location?

[black s13]

i just drilled and tapped the coolant bleed hole. reading is pretty accurate, however it is effected tremendously by the operation of the heater (~30 deg. difference)

[Onizuka]

I think anyplace that sends coolent to the radiator is an aweful place to put a temp sensor. My thermostat wont even open on real cold days with the heater on unless I floor it. I know because when I floor it the thermostat dumps all the cold coolent in the radiator into the block and the stock temp gauge takes a short dive. Check out the factory service manual and find a hose or turbo outside of the motor that always has coolent circulating through it.