TheSamba.com :: View topic - Great temp after new radiator...until a minute from home

Sat Apr 19, 2014 2:05 pm

We made our first trip after installing a new radiator in my 84. It was over 320 miles round trip, hither and yon, over hill, mountain, and dale with a handful of small "local" trips thrown into the mix. The temp was rock solid 99.98% of the trip. I have the GoWesty radiator baffle kit, but only the lower piece is installed. New fan switch was installed, too.

This was the temperature gauge for all 6+ hours of driving:

I finally thought "Hey, I have this thing running well and my problem is solved!"

It was hotter in Vegas when we returned yesterday than it was on the trip to Cathedral Gorge, but not bad, probably around 85°F. The last leg of the trip was from Alamo, NV to home. I had to stop on the exit ramp from the highway. Then, after two more green lights, turning into our neighborhood, I get the red light flashing and the needle climbing rapidly. I let off the gas and it returned to normal.

Coolant level is normal and was the same this morning and for the entire trip. Oil level was about a quarter inch above the low mark for the trip home, but I didn't add any. I changed the oil about 1,200 miles ago (Fram filter, but I have some Mann/Mahle filters now. Not installed.)

What.
The.
Hell.

Just when I'm feeling confident, here's a little curve ball to burst that bubble. The fan did not kick on at any time during the trip and definitely not when the light flashed.

Any ideas?

Temperature sensor? I think it was replaced by the PO, but can't recall right now.

Thanks in advance!
Jason

Sat Apr 19, 2014 2:33 pm

I'd force the fan to switch on to make sure it works. I'm sure theres a plug somewhere that can be jumped.

Sat Apr 19, 2014 2:56 pm

Fan is good. I checked it before I installed it.

Sat Apr 19, 2014 3:31 pm

Since it is an 84 with the early coolant level relay that low coolant level relay pegs the needle and blinks the led whenever it thinks level in the main tank is low. If it is the level relay that makes the needle jump then the fan won't come on because things are not really hot, the relay is making the temp needle peg, falsely, by design.

Or if the temp gauge wire at the engine should rub through or somehow make contact metal to metal then again the led will flash and needle will peg. Again the fan won't run because things are not really hot, it is a false reading.

The engine/coolant CAN'T instantly jump hot or instantly drop to normal. It takes time for the true temperature of a large mass to change. So any time the temp needle makes sudden swings you have to think it is due to a false reading and not true temperature. Then verify.

Mark

Sat Apr 19, 2014 9:35 pm

yeah, what mark said - it is the low coolant sensor. either it is malfunctioning or your level is low. make sure you check the actual tank (ie not the one behind the plate - the one in the engine under the blue cap - which is pressurized, so don't open (or do with *lots* of care) if the van is hot).

the sensor wire can come loose sometimes and cause false alarms, but usually it means your van has sucked down the coolant past the blink and peg level.

my temp gauge is dead. i have an after market gauge that works though, and tells me the actual temperature.

Sun Apr 20, 2014 2:23 am

I was gonna say blinky = coolant level. ^^^ those dudes are way more savey than me, and obviously have their stuff together.

Sun Apr 20, 2014 8:25 am

Couldn't respond last night due to Date Night...

Thanks, Mark! As an automation technician, I knew that something didn't jive between the "overheating" and the fan not kicking on, but the emotion of a blinking light coupled with years of driving my 71 Vert kept logic from kicking in with the "STOP THE ENGINE, YOU FOOL!" screams in my head. Red light = stop.

Plus, I own a 600# Kamado cooker, so heating large thermal masses is very familiar. Getting rid of the "why aren't you working??!?!?!?!" and looking at the radiator logically was what determined that the original one was clogged, but when your ride and the family's safety is on the line, it's hard to be Spock!

The boot to the temp sensor and the wiring for it is in less than perfect shape, so I will start hunting for an intermittent grounding problem.

It actually happened last night as we pulled onto the freeway and I had to "Zen Logic" down the urge to panic. Knowing what was likely happening probably added a few days to my life from the lack of stress. A few seconds later, it calmed back down.

If only they would have just blinked the light instead of pegging the needle, too.

Tom,
I had recently replaced the Overflow tank since my original one was cracked and my fingers went right through it. I also replaced the pressure cap that came with the Westy with a new one that I believe does not work, then the rear heater valve and radiator. It's been an ordeal, but I can say the knowledge gained is worth far more than the cost of the parts. The $4 pair of hose removal pliers from Harbor Freight have seen more use than I ever imagined!

Thanks again, guys!

Sun Apr 20, 2014 8:51 am

the pegging part makes you pull over though. :) it really is one of those conditions you don't want to ignore.

pressure caps can quite often arrive defective. do the squeeze test on your hoses to see if it is holding pressure. another cause for failure is the hose to the overflow (behind plate) having holes in it. liquid goes down hill easily, but doesn't get sucked up again because of small cracks in that hose (or not being tight).

my old overflow was like yours, cracked to hell. i only recently got a new cap for it as well - now it all looks new. and it'll be impressive once i put it all back in the van. the hose that connected the tank was leaking terribly (i bent it and held the ends deepest underwater - lots of bubbbles from the hose. :/

Sun Apr 20, 2014 9:00 am

you can diagnose the coolant level sensor by having the van running and giving the wire a jiggle. if it makes the warning trip, then just reseat it better. you'll need to turn off the van to get the blinky alarm to turn off though - once tripped it stays on until you kill the ignition.

Sun Apr 20, 2014 9:16 am

Did you know that you are supposed to be able to see the coolant level inside the Overflow tank?

...without removing the cap?

:)

I'm just thankful I didn't put my finger through the tank when we were on our PCH trip!

Sun Apr 20, 2014 9:17 am

http://www.carpartsdiscount.com/auto/parts/catalog/volkswagen~vanagon~84.html?3593=318326

That looks like the right fit.

Sun Apr 20, 2014 9:48 am

heh. well, you used to be able to check the coolant by what cracks it was leaking out of. keep in mind - that tank (behind the plate) is not the critical coolant level. what is under the blue cap is what matters - i'm sure you got that before, but just in case, since it is critical and people have made the mistake before of only checking the one behind the plate.

yes, that looks about right - although it is missing the rubber boot.

you can probably just clean up your old one - brush off any corrosion with screwdriver, gently bend contacts to be tight.