Hello All - Happy Holidays!

Wondering if folks can help me figure out what MIGHT be happening here. I say might, because coolant issues can be so strange.

I recently did a flush and fill as fall approached. Car was running cool to normal during the summer and fall. Not loosing any coolant. No issues.

At the time, I did replace the coolant tank on the wing (for some reason the name of that tank is COMPLETELY escaping me) as my old/original began leaking.

Filled as instructed here. Went smoothly. Been driving for weeks and/or a couple of months. Even some long trips with warmer/hot weather. Even with AC,,,,, an everything! No issues.

Car has not overheated or gotten anywhere near close.

Recently noticed, even with cooler temps as fall/winter approached - on short trips back and forth to work - she was running warmer than usual. And, would heat up faster! Strange.

Yesterday I went and cracked the fill spout inlet at the front center and it was as if the coolant was under pressure. I turned off the cap and as I did coolant pushed out. I closed it with out removing cap completely to seal it.

Went to the other cap (reservoir?), undid it, and heard a short but definite swoosh of air (couldn't tell if air was going in or out). Was able to pour 3liters of coolant 50/50 into the (reservoir?) tank before it was full.

A stuck thermostat? A blockage in the new tank? I've been thinking and thinking and don't know what's going on... Any ideas? Directions I should be going in? You help is greatly appreciated!

 

I should add:

When I took the cap off the filler neck, and water came out under pressure, the car was DEAD cold and hadn't been drive for 4days.... @ 40 degrees F or below even...

 

Hi Jay

Header Tank

Worst Case Scenario 'Head Gasket' (hope not though)

 

My immediate thought is at original fill you had an air pocket and you may also have restriction in header tank to atmospheric tank hose.
This is only way l can think of that would account for retained pressure in system. Centre fill cap is sealing type and header tank pressure cap vents to that atmospheric tank hose which if blocked may prevent venting.
Quick check would be remove atmospheric hose attached at header tank fill neck and run system like that. You will lose about half litre at first warm up after fill and thereafter nothing more. Plenty of capacity in header tank to cover that.

 

That is likely the most relevant clue. The system is designed to sort of 'breath' as it cycles cold to hot to cold, and you shouldn't have any pressure at that point. Something is blocking the proper expansion and contraction through the cycles. I would read Grant's sticky on "V12 cooling system maintaining" and the atmospheric tank hidden in the wing/fender as a first step. IIRC, the hose to it can get clogged and/or can collapse under pressure, and the tank can fill with what Grant describes as 'mud'.

 

Thanks Mac...

So, I did some stuff yesterday. Replaced front soft brake lines, which went all kinds of smooth! I shocked myself. Had been dreading it as it's possible to go from what seems straight forward,,, to seized connections, making new brake lines and rounded of line nuts. Shweeeeeeeeew...

Anywho, I opened the wing and removed the expansion tank bottle. It was dead empty. I hadn't been in there for a long while... I think not since I first started working on the car, and it was nasty inside. Also, there was a 2-3 inch section of STEEL tubing that connected one section of hose to the other from the header to the tank. This section significantly reduced the ID of the hose to hose for this short stretch. It was also caked and corroded inside. Still, I was able to blow air through the line from the header* (thanks OB) side to the expansion tank.

So I cleaned up the tank, cleaned up the short section of steel tube and reused it (I shouldn't have), filled the expansion tank half full, put a ton of waxoil in the area back there and sealed everything back up.

Just drove into work and she is warming, cooling and running at a temperatures I am more familiar with. Things seem "normal"...

Still, I don't understand the filler neck being under pressure, the header tank being so empty and the complete lack of fluid in the expansion tank (since at least air was able to pass). Mysterious... I'll be back in there, no doubt.

Was also able to rehang the RH exhaust over axle pipe with a new rubber exhaust bushing bit. Tight in there. Did find that the metal U shaped carrier was slightly cracked on both the legs that bolt into the cage. Looks like I'll be back in there as well. Good thing,,, that little knocking and tapping is no more. Exhaust pipe tapping on the bleeder valve line for the easy bleed set up on the rear brake caliper... More sound than I realized was being transmitted into the car than I thought.

More to do, more to come, as it is...and always shall be, lol