engine overheat prevention alarm

[CRSMP5]

orcoaster.. looking under it will not help at all.. this is looking inside the waterpump housing.. have to remove thermostat.. and to me id guess you got pump #4.. plastic... sounds like its starting to slip.. why plastic is not a option.. even though its so common people have issues..

if looking under it to see if room to fit thermo switch.. again. nope.. cannot see where it goes that easy either..


another reason for pump temp is to compair to head temp... under boost you can see a head temp go up vs block temp.. my old bae caddy set up i could watch it under its 7psi of boost raise head temps vs pump temps.. a 2 way toggle switch will allow you to switch between readings.. yea ive played with this set up way too long..

you cannot use the thermostate area... i am talking about placing a sensor on the housing, back side so its between housing and block.. tucked away in such a way you could consider it a way to hide wiring.. why no pics.. cannot see the thing once installed.. 

[92EcoDiesel Jetta]

IDK, I don't have an owners manual I'll check with someone who has one. Do you know where the signal for that overheat warning light comes from?

 The '91 Jetta has an overheat warning light in the dash doesn't it?
 Shares the low coolant flashing light.

[92EcoDiesel Jetta]

That Acme neck is nice ($68 btw). Are you suggesting using one of the extra ports in the Acme neck to add a sensor to measure coolant level? If that can be made to work, it may do the job. A float switch will have to be custom and very small. Maybe a sensor to measure conductivity of the coolant? Is G12 conductive? I know tap water is conductive but not distilled water. If tap water is used, then I can program the multimeter to sound an alarm if the resistance drops from it's normal value. Have to find out if the multimeter has the alarm feature on resistance.


 

to get around the leak or loss of coolant not giving you a reading couldn't you do the fancy acme neck in conjuction with a normally closed circuit through the coolant so that when its level drops it would also signal the warning? Similar to what they use for idiot light on level sensor for overflow bottle? Knowing that hot water rises would it be possible to still overheat a head if you were monitoring at the lower stat housing?Especially since the coolant wouldn't be making a its rounds up top if it had dropped and the cast iron blocks take considerably longer to heat up than the aluminum head? Just askin, and following intently since I have always wanted to devise a shut down to keep the SIL from killing another vw(idiot lights and gauge warnings are meaning less if she has someplace to go)!

[92EcoDiesel Jetta]

Ever since I replaced my head gasket, my coolant temp (per the gauge) has dropped substantially below the middle mark at hwy speed, it goes up to the middle mark if I let it idle a while. I am wondering if the sensor is being cooled by the rush of cold air at hwy speed. I will try wrapping a blanket around that flange where the sensor is located to see if it makes it read higher.

I modified my glow plug relay so it is manually controlled. No wiring changes to the car. I took apart the glow plug relay and cut a trace on the PCB and soldered wires to the spade lugs and hooked them up to a rocker switch and a chime. The glow light is now directly across the glow plugs and not on a timer. I like this much better. On a hot engine, I do not glow the plugs at all and it starts up fine. I can go back to stock glow plug operation anytime by just changing the glow plug relay to a non modified unit.

CRSMP5 now you are going to make me crawl under that car and look at the waterpump?  I was going to anyway as on my trip down from Portland tonight I was running real cool, under the 70 C mark on the gauge until I stopped long enough for a p break and the temp went up to 85 and held there.  I was on the slower part of the route near towards the coast by that time.  Once I dropped 10 mph off the speed the engine seems to warm up a bit.  Likely get better mileage for it too.

I like that multiport neck and may look into buying one as I really have need for an additional sensor for the VDO gauge I salvaged for a GTI.  I have it tapped into the one for the glow plugs and it makes them stay on for a few seconds after the engine starts.  Not a bad feature but it also turns the glows on no matter how hot it is outside. 

Have to get back to you on the type of WP.  It is dark and scary out right now.

[BigVWman]

The coolant is conductive that is why i mentioned it, On some of the vw's i've owned they even use a two prong conductive sensor in the overflow tank to trigger the low coolant light.

[CRSMP5]

all the "round" ball style bottles have float built in... usually hooks into the led in the gauge.. when it flashes either low or overheat..

pre ball style (87 and older) has a fugly screw in sensor that used coolent to complete the circuit.. back in td rabbit had seperate led, rest were part of led gauge..

[R.O.R-2.0]

all the "round" ball style bottles have float built in... usually hooks into the led in the gauge.. when it flashes either low or overheat..

pre ball style (87 and older) has a fugly screw in sensor that used coolent to complete the circuit.. back in td rabbit had seperate led, rest were part of led gauge..

the ball style ones, is it a float switch? have an open, or closed circuit, or just a varied resistance?

guess i could test the ones i have and find out myself.. lol.

[ORCoaster]

Spent to much time doing other needed work on the car to pull the water pump off and look at it.  Trying to get it all cleaned and polished after last weeks paint job.  So still have no idea what pump or impeller type I have.  As long as it isn't leaking and not overheating I will leave well enough alone.

[92EcoDiesel Jetta]

I just measured mine (ball style Meyle from Autohausaz) with a digital ohmmeter. With G12 and tap water, I got 1 meg ohms. I put the probes inside the ball touching the coolant and got a similar (slightly higher) reading. That means it is not a mechanical float switch but a resistance probe. Maybe this Meyle expansion tank is crap (lousy material on the probes?) because I did not get a low coolant light and blew a head gasket a couple of months ago.

the ball style ones, is it a float switch? have an open, or closed circuit, or just a varied resistance?

guess i could test the ones i have and find out myself.. lol.

[fatmobile]

IDK, I don't have an owners manual I'll check with someone who has one. Do you know where the signal for that overheat warning light comes from?

 The '91 Jetta has an overheat warning light in the dash doesn't it?
 Shares the low coolant flashing light.

 Touch the temp sender wire to ground and it should fool your cluster into thinking it's an overheat, the light should flash.
 With the low coolant warning light; if you turn on the ignition and the light doesn't flash; your coolant is already too low for it to work.
 It is an RC circuit, not just resistance.

[92EcoDiesel Jetta]

 Touch the temp sender wire to ground and it should fool your cluster into thinking it's an overheat, the light should flash.
 With the low coolant warning light; if you turn on the ignition and the light doesn't flash; your coolant is already too low for it to work.
 It is an RC circuit, not just resistance.

RC circuit! That makes sense now! I was wondering why the low coolant light didn't react immediately when I unplugged the connector to the ball.

So you're saying the temp sender is also an overheat sender? Did VW design it that way? It must work by conduction in the overheat mode since there was coolant loss and there is no coolant in contact with it. It may work ok in the old aluminum necks but not in the plastic neck in my 92. Even if aluminum, it sticks out too far into open air and by the time the overheat light comes on, the engine is probably already toast.

[92EcoDiesel Jetta]

Did an experiment where I disconnected the connector from the coolant ball and started the engine, the low coolant LED flahed, indicating low coolant. I shut the engine off, immersed the connector into a cup of water and started the engine and the LED did not flash. This shows the low coolant circuit measures the resistance of the coolant to sense coolant level, with an RC circuit (per Fatmobile).

Should the buzzer have sounded? I don't think my buzzer is working. Where the hell is the buzzer? Maybe it don't matter since I'll be getting 6 85 DB piezo alarms from Ebay soon. I plan to have all kinds of audible warnings: Head temp exceed, low coolant, low oil pressure, low oil level. My Auber instruments multimeter arrived yesterday and I'll be playing with it. He's got a 100% positive feedback so I'm not expecting any problems with it.