legacycentral bbs

I check my 93 Turbo's coolant level by taking off the filler bottle cap and looking at the level. It's been consistently full, right up to the top. The overflow tank level's also been right at the full mark.

This morning I checked the level and the bottle was low. The overflow bottle level was a bit higher than the full mark. It appeared that the total amount of coolant in the car was still the same as before (meaning I have no leaks) but it seemed weird to me that the coolant would be in the "wrong" place.

I confess that I don't fully understand the ins and outs of our cooling systems... I felt it would be safest to top up the filler bottle and siphon out coolant from the overflow tank, so that's what I did. The car seems to be okay... I checked the level again in the evening after the car was cool and the levels were both "correct."

Was this normal, or does it indicate some kind of problem?

From what I've seen, the overfill bottle is completely meaningless unless you run realllly low on coolant (which is very very bad) and then the car will drop below full. Coolant tank being low usually means inner circuit leak (water jacket, pump, heater core, but no radiator), especially with the overfill staying full. Check the banjo bolt on the turbo, all your lines, and see if your windows fog unnaturally - the first ones are self-explanatory and the last is a sign of heater core leakage. Mine did this yesterday... had to bypass the heater core .

Thanks for the reply, Brat...

I've looked thoroughly for leaks and haven't found any... And there aren't any signs of coolant spray from when the engine is hot...

The weird thing in this case is that the overfill tank didn't just "stay full;" its level increased by about the same amount that the filler bottle's level decreased.

I'm starting to think this may have just been because the turbo was pushed hard that time when I parked. Subaru's whole convection-cooling system on the turbos is designed so that the coolant in the turbo vaporizes and rises to the filler bottle, and the partial vacuum draws fresh coolant from the passenger side cylinder head. Maybe that vapor went all the way to the overflow tank before it recondensed?

Have any of you other turbo guys ever noticed this? If not, I suppose I'd best be purchasing a coolant temperature gauge ASAP to keep a closer eye on things...

Had you refilled your coolant any time recently? It didn't suck the coolant into some air pocket did it? I'd check the coolant resevoir level frequently (when it's somewhat cold of course). If it doesn't do it again, maybe the system just hiccuped .

I did recently change the coolant; that's one of the reasons I've been checking it often.

I know the coolant didn't disappear anywhere because I know where it all went.

I've read through the manual and looked at the car again and I think what I found is relatively normal.

The turbo cooling system is designed so that vapor coming out of the turbo ends up in the overflow reservoir temporarily. As the whole system fully cools, the partial vacuum caused by the coolant's contraction pulls some of it back into the filler bottle. I just happened to check the levels after the turbo had cooled but before the whole engine had fully cooled.

I'm getting a coolant temp gauge. Anyone have any recommendations? I definitely want an electric one with a sender because I don't want 200-degree corrosive poison coming into my passenger compartment. But I don't want to shell out the big bucks either...

Thanks for the help, Brat.

Excuse me for being stupid, but isn't the factory temp gauge a coolant temp gauge? Or is the gauge you're looking for, vrg3, a far more accurate one?

The latter. The factory gauge is almost just a toy; it has basically three indications: "warming up," "warmed up," and "oh crap, save up for a new head gasket!"

I want one to read in degrees.

Or I may just try to tap off one of the stock sending units. The FSM has a little chart of the ECU sending unit's resistance vs. temperature. I'd just have to figure out how the ECU reads that signal.

My suggestion is to replace the cap. Even a cheap on should give you an idea.

Thanks, ciper... I actually am starting to suspect this cap might not be doing its duty the way it should. I sometimes see a little bit of dried antifreeze around the lip.

But just so people know, the FSM does say that the vaporized coolant from the cooling turbocharger is meant to temporarily end up in the overflow bottle. It's not meant to stay there.