I'm beginning to think this is a windup

How much water are you actually losing per ride Karl ? have you actually measured the amount you have to top up ?

 

what is a windup?

In a week I went from the expansion tank being just below the maximum line to having the front section of the tank being empty.

 

a windup is where someone posts something ficticious to 'wind people up'

To be meaningful we need to know how many miles your car has done in that period ie is it draining out all over your driveway or are you doing 2000 miles a week ? Your mileage will give everyone some idea of how significant your leak is (sounds bad) and where it is likely to be going.

My guess is still that you have a small head gasket leak between one of your cylinders and the coolant system which is forcing coolant out as you drive.

You need to monitor your exact coolant loss over a 24 hour period ie how much it takes to top up the header tank again each day

 

I can see someone posting fictitious political opinions to "wind people up" as you say, but I don't know why someone would do it about their car troubles. And that's definitely not what I'm doing.

I drove it about 100 miles last week, with 20 or so being hard miles at an autocross test-and-tune and three pulls at a dyno. I've driven it 30 miles around my city and had the coolant drop an inch or so down the top of the expansion tank. The issue I have now is I don't like driving the car when I think to myself all the time will it blow up on me? I'm nearing the point where I might just have the engine pulled apart and refreshed just for peace of mind, and it will most likely restore some of the power I appear to have lost over 116k miles.

 

At this point, you need a new shop. There's little to nothing anyone can do to diagnose this without their hands on it. And the people who have had their hands on your car are obviously not the right ones or this would be done and over by now.

 

you definitely do not want to be thinking of pulling the engine apart until you have got definite proof there is something wrong.

As long as you keep an eye on your coolant and engine temps and your fans are working don't worry about it.

If your local shop haven't found a leak then it has to be the coolant system being over-pressurized by compression gases . That much liquid loss would definitely show if it was into your oil wouldn't it . As Daryl says you need to find a shop that know what they are about

It should be very easy to connect a tyre pressure guage into your coolant system somewhere to monitor your coolant pressure real-time whilst driving.

 

[ B]Use a block tester!!!!![/B]


As I said before it is very common to see head corrosion that will lead to this exact problem.

 

Just called the shop, asked about testing the coolant for compression gases and he said they did that already with a negative result. They were going to check the heater core and get back to me, but I have not had a wet floor or coolant smell in the cabin so it would seem unlikely that the problem would be there.

 

Seriously.....get a new shop. This should be done by now.

 

Dropping it off at a different shop on Thursday

 

Yeah - you won't see any issue IF the test is done on a cool motor. Heat expands metal and if there is a crack in your head, you will only see it on a hot motor.

The only way to truly test this senario is to pull the head and have it 'heat tested' (I believe magna-flux may be the proper term for this process)

Yes, I went through this myself - my car would loose coolant on the racetrack, but during short drives, little or no loss of coolant. Pressure tests always came back fine.

-Z

 

Very similar symptoms for me. Pulled the head, looked at the gasket and thought "dammit. It's fine". Then I saw this:

 

I know this is out in left field - but bear with me.

I had this same problem - could NOT find a leak that was dropping the coolant level to just below minimum, but usually no lower. I would fill it, and a day or so later, back to below minimum.

Turns out it was the hose from the block to the bottom of the expansion tank/reservoir - some idiot mechanic had routed it across the top of the alternator, and the alternator's cooling fan blades had machined a thin spot, and a pin-sized, hole into the hose.

The hole was small enough to spray an invisibly fine jet of coolant when under pressure, but once the pressure dropped - no leak. I figured that a large amount of expansion room in the system (with low coolant) kept system pressure low enough that the hole would not leak.

Like I said - left field, but worth a look.

 

Think I might finally have an cause, though it's not what I was hoping for. After having a third leak found and fixed, I drove it for almost a week but the coolant level kept dropping. I pulled the spark plugs again to check the piston heads, and I could see the lower half of the of the piston closest to the firewall was damp =/

 

well at least now u know what you have to do

are bets going down on size of headgasket gap?