[LiquidRS]

There is a leak somewhere in the coolant circuit. Get the shop to do a more thorough pressure test. Leave the car over night on pressure and then do an inspection the next morning, allowing for cylinder head pressure drop. The car has numerous heat exchangers, pipes with O rings, hoses, radiators etc, the shop needs to go through it all with a fine tooth comb.



FYI I've done 5k kms with my car in the last 12 months, coolant level has not fluctuated one iota!

Originally Posted by JSH

I cannot figure out why my upper reservoir loses fluid every time I go on a cruise. It sits overnight, and when I go out the next day, the fluid has dropped. The fluid comes back up some after I loosen the cap, but never to the cold fill line. My shop has replaced the cap and pressure tested the system. WTF?

[JSH]

Originally Posted by Evansa22

Use a fluid transfer pump, $7 at harbor freight. Their is no drain

I bought a siphon. Tomorrow, I'm going to drain the bottom tank down to half full and follow the procedure in the manual. It's spitting fluid out of the two holes in the top of the bottom tank, which is too full.

[JSH]

Hopefully this is the final chapter in this story.

Every day, I filled the top tank and went for a drive. The next day, the top tank was always empty. The reason was that the bottom tank had far too much fluid in it (an inch from the top). During and after a drive, the fluid would expand, rise to the top of the tank, and drain out of the two holes, much like my intercooler tank works.

So, I bought a $6 siphon and drained the bottom tank to the cold fill line. I then followed the procedure in the manual. Why do I never look to the manual to solve any problem?

[JSH]

My last post wasn't the final chapter. Almost every day since then, I have followed the procedure by syphoning the bottom tank down to the mark and filling the top tank. After four or five days, the bottom tank stayed at the marked fill line, but the top tank was almost empty. Today, the coolant (Stay Frosty) is at the cold fill line of the top tank. The one thing that is certain is that the system had way too much fluid when I started all this. It should stabilize at the correct levels shortly.

[JSH]

The upper tank is empty after every drive that I take. I then siphon fluid from the bottom tank down to the required level marker and pour it back into the upper tank. And the cycle repeats over and over with no resolution. So I need to buy a new reservoir. Anyone have a suggestion like a Granitelli maybe.

But the caveat to all this is that the shop performed a pressure test on the coolant system back when I started this thread, which is inconsistent with everything that I've written here

[KingLT1]

How can a coolant reservoir go bad unless it's cracked and leaking? It sounds to me like your coolant system is getting excessive pressure and being forced into the overflow section of the tank. The bottom is the overflow, the top is the reservoir.

[JSH]

Originally Posted by KingLT1

How can a coolant reservoir go bad unless it's cracked and leaking? It sounds to me like your coolant system is getting excessive pressure and being forced into the overflow section of the tank. The bottom is the overflow, the top is the reservoir.

I agree that coolant is being forced out of the top tank, except how do I determine the source of the excessive pressure? The engine coolant stays around 180°F, and there are no unusual spikes. It has the stock pump. I can't think of any changes made to the system other than using Stay Frosty in place of 50/50, but that can't be an issue. A couple of months ago, it was spraying a little fluid from the top tank, so I replaced the cap, and that stopped. Maybe a jammed thermostat? All cylinders have been leak tested.

I've considered driving it with a dry top tank to see what happens.

[KingLT1]

Originally Posted by JSH

I agree that coolant is being forced out of the top tank, except how do I determine the source of the excessive pressure? The engine coolant stays around 180°F, and there are no unusual spikes. It has the stock pump. I can't think of any changes made to the system other than using Stay Frosty in place of 50/50, but that can't be an issue. A couple of months ago, it was spraying a little fluid from the top tank, so I replaced the cap, and that stopped. Maybe a jammed thermostat? All cylinders have been leak tested.

I've considered driving it with a dry top tank to see what happens.

That is a stumper for sure. Might be worth a shot to change the T stat?

[Gunkk]

Or the tank.

[JSH]

Other than the pump, pressure in the coolant would most likely be from a cylinder. We have not run a borescope to look for fluid, but we did a leak test.

[JSH]

Nothing has changed. I fill the tanks to their proper levels, go for a drive, and the system has emptied the top tank into the bottom tank. I then refill the top tank by syphoning coolant from the bottom tank. The top tank's volume is exactly the same as the excessive amount of fluid in the bottom tank. The total volume of fluid doesn't change. So it's not leaking fluid. It simply doesn't return fluid to the top tank. Could the top tank have air pressure?

[RobZL1]

Any chance you have a small leak from the top to the bottom that is only exposed under pressure and/or heat?

[JSH]

Originally Posted by RobZL1

Any chance you have a small leak from the top to the bottom that is only exposed under pressure and/or heat?

I don't think so. The total volume of fluid doesn't change. So it's not leaking fluid. There are no signs of a leak.

When and how does the system return coolant to the top tank during regular operation?

[Gunkk]

Originally Posted by JSH

When and how does the system return coolant to the top tank during regular operation?

Syphon/Suction/vacuum as the coolant cools down after the car shuts off. It's supposed to suck the expansion tank fluid (that expanded when it was hot) back up into the top tank. This is how all modern expansion tanks work. It's just counterintuitive with our cars because of the odd arrangement of our multi-tank setup.

I suspect yours isn't working properly because there is a small air leak in the tank that is breaking the syphon and preventing the suction mechanism from occurring, and thus the bottom tank fluid never gets pulled back into the top tank.

Hence why I think replacing the tank assembly will solve your problem.