coolant overflow tank empty

[ghiafreek]

I checked up pressure tank (one accessible with engine comp cover removed) and that tank is filled. Checked overflow tank (behind license plate) and it is empty. Can I just fill up overflow tank and be on my way?

thanks

[Dana Champion]

The overflow tank is non pressurized. There are fill marks on the tank. Fill it with your coolant mix, or distilled water. Drive it, and check the tank.

[Gnarlodious]

Yes and as along as the pressure tank is topped off you are OK. If you think the system is leaking, get under there while it is pressured up and look for a drip. If you can’t find a drip, it may be that the coolant is evaporating out due to a leaky head gasket. If so, best to catch it early.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[ghiafreek]

Thank you both. Was holding tight waiting for response. Trying to get it on the road. I'll top it off and start her up.

[E1]

In lieu of pressure-testing your cooling system, first thing I'd do is fill the overflow tank to the center point and crack open your radiator tap when good and hot and fast-idling -- to confirm or eliminate if any air's in the system.

When there is, coolant is drawn into the expansion tank in a vacuum while cooling after shutdown. If you get a fair amount of air hissing out, and/or bubbling out, to me that's enough air to explain an empty overflow tank.

It's also possible the system is good now if indeed the coolant was drawn in. The system does a reasonable job of eliminating minor, residual air.

I fill it cold to the midpoint at first, to study what's going/gone on. Watch the level fluctuations for days, when hot the level's up (maybe half the distance between the high and low mark), and inversely.

If the level's consistent when checked cold several days in a row, and the air's all out, you, too can breathe.

I've had a few scares that point to head gasket issues, like bubbling coolant (bad blue cap), and other times I couldn't explain. But in the end the coolant level was consistent once all the air was out, and I do wonder if residual air may well appear in the overflow as minor bubbling at idle. I read many projections of head gasket issues that turn out to be something cheap.

All this assumes you're very careful and conscious of watching for leaks and going easy on things until cured.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[ghiafreek]

Thanks for added info. I'll definitely look at that. My first classic vw waterboxer.
A lot going on.