Temperature Sensor Gremlin on the Move

[kfriedman00]

SYMPTOMS OVER TIME:
- flashing coolant light and overheating according to temp gauge after gas fill up
- jumped coolant level sensor with paperclip, eliminated issue
- as I was parking at home, issue returned, jumping coolant level sensor did not resolve
- unplugging coolant temp sensor with coolant level sensor plugged now resolves issue

QUESTION: How did the gremlin move from the coolant level sensor to the coolant temp sensor?



FULL STORY: I recently purchased a 1984 Vanagon GL and immediately encountered a problem haha. The previous owner did a lot to overhaul the vehicle (entirely replaced brake and suspension systems, replaced radiator fan system, etc) and the vehicle runs, brakes, and shifts very well.

After driving for 15min with no issues, I stopped to fill up the tank. As soon as I pulled away from the gas station, the temperature light began flashing and the gauge skyrocketed to max. I pulled over and shut the engine. It did not feel particularly hot, no coolant leaks had emerged, and all the coolant hoses were warm but not too hot.

I let the van sit for an hour until I could put my hand directly on the block confirming it was cool. I put the key in the ignition and moved it to the run position, but did not start the van. The same flashing light and gauge skyrocketing occurred (I'm not talking about the startup flash of the coolant level/temp light, I know that is normal).

The coolant level senor has the GoWesty Coolant Level Sensor Conversion installed on the expansion tank. I removed the plug, jumped it using a paper clip, and the issue disappeared. I drove home (1hr drive) with the temp gauge reading properly (it rose as I drove, steading on operating temp at 1/2 max).

As I was pulling up to my residence, the same issue arose: flashing coolant light and skyrocketing temp gauge. I shut the engine off, checked the paperclip, nothing has changed. I try jumping with a clean, fresh wire now that I'm home; issue persisted.

I pulled the single connector off the coolant temperature sensor installed in the thermostat housing and the issue subsided. When I connect this connector to ground, the issue returns (as expected: if this connector goes to ground, resistance becomes zero and the system believes temperature is max as the temp sensor reads lower resistance at higher temps). So, I've concluded my temp sensor is bad and ordered a new one.

If I run the car with the coolant level sensor connected and the coolant temp sensor disconnected, the issue now does not occur; however I now no longer know the temperature of the engine as the coolant temp gauge is disconnected.

My confusion: how did the temp reading issue gremlin move from the coolant level sensor to the coolant temp sensor? I highly doubt that the coolant level sensor failed, then stopped failing right as the coolant temp sensor began to fail.

[skills@eurocarsplus]

what condition is your instrument panel foil in? that is really the only place the 2 gauges meet up unless you have an issue in the harness, but seeing how they are routed, it would be the last place I'd look. The foil however....
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[crazyvwvanman]

You have the early version of the coolant level relay, 83-84
You should replace it with the later type, 85-91

The early version blinks AND pegs the temp needle when the coolant is detected low, even when engine is stone cold.
The replacement coolant level relay versions only blink the led and leave the temp needle showing truer engine temp.


EDIT: from old thread!!!
3 versions of the coolant level warning relay

These are the 3 versions of the coolant level warning "relay" used in Vanagon 1983-91. The tall 43 unit is the cursed early first try and should be removed and discarded if encountered. Either of the short ones is fine.

The tall one pegs the temp gauge hot and makes the temp led blink when coolant is sensed low in the main tank. The shorter improved later versions only blink the led and let the gauge read what the temps actually are.

Mark

[skills@eurocarsplus]

after thinking more about it...

yes to the relay and you may have a capacitor getting ready to take a shit in the temp gauge itself. usually, the LED will just blink despite everything else being good
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[kamzcab86]

[E1]

Before delving into rabbit holes, put more coolant in.

The coolant contracts while cooling and will make the light blink until the coolant is hot again and expands just enough to cover the sensor.

The levels also fluctuate a little depending on several things, like having air in the system and where it happens to get lodged from day to day (like in the heater core).

I’d also bet a ten-spot it’s not overheating at all. It’s quite possible the two conditions aren’t related… but seems like you and others do and y’all may well be right!

To discount the blue coolant cap being bad (if you have the stock cap), see if your overflow tank level is going up at all or staying consistent each morning (when cold). Mark the overflow level with a Sharpie, if it’s gradually rising every day, you might try replacing the blue cap.
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1984 Westfailure/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s
AI has spoken to further illiteracy, to steal, to cheat, and to replace humans

"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere." — Colin Chapman

[kfriedman00]

I replaced the relay with the shorter 43 and the issue resolved itself. Now having new issues related to the coolant system, but the flashing issue has disappeared.

[kfriedman00]

UPDATE: Now running rich and coolant level light still flashing.

I replaced the relay, flushed the coolant system (it had air in it), and now the system does not overheat. The flashing light disappeared briefly (per my last post) but came back about a day later. The engine is not overheating, but the coolant level light flashes continuously and the motor is running extremely rich.

Once it warms up, it:
- blows black smoke
- has an inconsistent idle
- surges at consistent throttle
- stalls on occasion

I replaced the grounding strap, cleaned the grounding points, replaced the terminal connectors on all the grounding wires, changed the (very very dirty) spark plugs. No luck. Temperature reads correctly but once warm it's a nightmare.

[brickster]

Have you tested the resistance of the sensor at both cold and warm coolant temperatures? It’s a good idea to test it directly and via the computer loom to rule out wiring issues between the sensor and computer.
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1984 Campmobile Automatic

[kfriedman00]

As @brickster recommends, I'll try testing the sensor later this weekend. Wanted to provide an update: replaced the O2 sensor to great success and eliminated my rich condition. The van drives much better now, though the coolant level light still flashes, but only sometimes (I'd say half the times I drive the light is flashing the whole drive).