Intermittent temperature gauge flashing (again)

[MootPoint]

I've looked through a bunch of threads on this issue but none seem to be quite like my situation.

My temp warning light starts flashing when I'm accelerating or otherwise have the engine under load, say downshifting to 3rd on a hill. When I let up on the gas, even the smallest amount, and return to cruising speed, it stops flashing. It mostly seems to happen between 3-3,500 rpm though not always; sometimes it's a bit lower. I'm thinking perhaps its simply a loose wire in the circuit somewhere that wiggles more when the engine is working. I repaced the wiring for the temp gauge this spring after packrats chewed it up. Grrr... If I recall a post from tencentlife, there are two circuit there, one for the gauge and one for the blinky. As far as I can tell, my gauge doesn't move.

This has become more important lately as my oil temp gauge isn't functioning at the moment (oil pressure gauge is OK) so the water temp is the only thing I can monitor. This makes me nervous.

I did see that air in the coolant lines can cause the problem and I did have the cooling system flushed this last fall and this was the first time I've run the van since then. Perhaps..but any other thoughts are welcome.
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1984 Westy with tencentlife power!

[skills@eurocarsplus]

you're coolant level is dropping at higher RPM's so the light comes on

i'm betting you're low on coolant
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[turbotype1]

[MootPoint]

Actually, if anything my coolant level is too high!. Before I left on my trip on Wednesday AM I checked the coolant lever and I couldn't quite see the level through the 37 y/o old plastic container but it looked as if it was below the "max" line so I added a little H2O. Then I saw it was actually actually above the max line by about a half-inch. Would too much cause a similar flashy result?

So it was doing the flashing thing both before and after the coolant addition. Hmmm....
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1984 Westy with tencentlife power!

[davideric9]

No Max line on the coolant reservoir - expansion tank in the engine compartment on the driver's side. Only max line I know of is on the overflow bottle behind the license plate. The blinking light low coolant sensor is in the reservoir tank.
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1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012)

[4Gears4Tires]

[SurfaceRust]

I agree with the above. It sounds like you are adding to the expansion tank and you need to add to the reservoir.

You could start the van with the reservoir cap removed. Move the throttle in the engine compartment and watch the coolant level. It should drop, and is probably dropping below the minimum for your sensor. While giving it throttle add the coolant to the reservoir till full. Put the reservoir cap on quickly and let the throttle out. Problem should be solved.

[MootPoint]

Ha! Thank you! Having only owned the Westy for 15years (!!), my naive assumption has always been that since the expansion tank had the easily visible max/min marks that it was the indicator of correct fluid level. Silly me! As I mentioned above, I had the system drained and flushed last fall and perhaps the shop did not fill the reservoir fully or check it after filling.

Thanks. I check that out. If you don't hear back from me it's because all's well. I don't hang out here as much as I used to; I probably need to rectify that.
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1984 Westy with tencentlife power!

[4Gears4Tires]

I'm 99% sure it's their fault. They probably filled it all the way when the engine was off. If the engine is running, the fluid level drops. That's why it's important to fill the reservoir while the engine rpms are held at 2000rpms. Or use a vacuum to evacuate the system and then fill.

Hopefully they sort it out.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[MootPoint]

[bobbyblack]

Ahh, so... The level in the expansion tank (the one NOT accessible from the licence plate door) does lower at higher RPMs. Further, the slightest leak somewhere can go unnoticed for quite a while, and this can lower the level a little more than usual. As per normal 'bleeding the coolant' you need to have both heater cores open (if you have two anyway, usually there is one under the rear bench, and one up front. Anyway, those can hold air, and if you turned on your heat, it could result in the level going lower. Funny thing about heat-up and cool down of the engine is that after getting to running, and cooling off, there should be a vacuum build up in the expansion tank, resulting in fluid from the overflow being sucked in. In that case, it would be self healing as you run/let cool the engine.

But, yes, check the wires that attach to the sensor that goes into the expansion tank, corrosion has stumped many a Vanagoner in the past.

My usual approach to bleeding is to back my rear up a bit of a hill, run the engine a bit with the expansion cap open, and add fluid there. Then run it a bit longer with the tank cap back on, and go open the radiator plug a little, doesn't need more than half a turn really, don't take it out, you'll loose it, and its hard to get back in anyway.
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[MootPoint]

Thanks. I took out my rear heater core years ago; it was leaking and I never used it anyway here in the stinkin' desert. Plus I like the extra under-the-seat space. But I hadn't considered the front core. As mentioned up-thread, I had a shop drain and flush the system earlier this summer and I bet they didn't touch the front.

I expect the two-way travel of the coolant to and from the expansion tank and I was surprised that, even after warming up during my campground test that the residual coolant in the expansion tank was still cold. After driving it for an hour or so (light blinking occasionally), it was slightly warm, but not as hot as the overall coolant under pressure. I was wondering if the coolant "warmth" was simply coming from the engine heat, not the vacuum process.

Thanks for the info!
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1984 Westy with tencentlife power!

[bobbyblack]

Now that is a new bit of info right there. You might have a faulty thermostat.

Also, there are some add-on kits that can help bleed the system. One by intrepidoverland.com [shop , Vanistan] is automatic. Purdy cool...

Hope you get it sorted!
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[MootPoint]

Thanks! I'm on very good terms with Chris/tencentlife/Vanistan as he build my engine, thought I don't think his bleed device existed in 2010 or he would have suggested adding it. So I'll check with him.

I considered the faulty thermostat but the front fan sees to kick in at times, just as it always has, mostly when idling for longer periods of time and runs for a while after I shut off the engine, also as it always has. And even the, the blinkly light doesn't come on, only when climbing under load.

Once again, thanks!
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1984 Westy with tencentlife power!

[4Gears4Tires]

If my light comes on at any time other than just after starting the van, I'm pulling over, removing the engine hatch, and checking my coolant level. I guess I'm just paranoid.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[SyncroHead]

The trouble with the "low coolant level" diagnosis is that the circuit that turns on the light is "latching". Meaning that the light is supposed to stay on if coolant level is too low until the coolant level is back up again and you've turned the key off and then back on again. This is so that the system is sure to catch an intermittent low level and keep warning you until it's corrected. Works the SAME way if there is a faulty level switch or faulty (open circuit) wiring to the level switch.

I suspect it's faulty electronics in the temperature gauge which drive the light.

There is a fairly common situation with these electronics where the capacitor in the gauge gets "lazy" and won't keep the light from blinking. I've had this situation in my '87 Syncro for years. The way to diagnose the faulty capacitor is when starting the van, turn the key to the ON position and then WAIT 7 or more seconds before turning the key to the starting position. This gives the capacitor time to charge while there's no drain on it.

While the above condition is NOT the same as yours, it would be interesting to see if this delay while starting changes your light's behavior.

Jim Davis
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