North American Turbocoupe Organization

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Took the bird out for a drive today and as I always do, had a very spirited drive. 

I noticed when I got home and was looking under the hood that the coolant level in the overflow tank was lower than usual. 

I recently changed the stock radiator to a big 3 core aluminum radiator. I’ve driven the car twice since the radiator change. Is it possible that the radiator/coolant system is/was burping air hence the lower coolant level in the overflow tank? 

There are no cracks in the tank. I haven’t checked the oil for coolant yet (blown head gasket?) but I didn’t feel any changes in power while doing some wide open pulls. 

What’s everyone’s thoughts? Anything to check in particular to rule some things out?
It takes my overflow tank 2 or 3 heat / cool cycles after a coolant change for the level to stabilize. After a coolant change I fill it to the FULL HOT level with coolant at ambient temp. After several drive cycles it stabilizes at the FULL COLD make or a little above.
Thank you Jeff; I had to look back, yesterday actually makes 5 times that I've driven the car since the radiator change. Do you still think it's possible that the coolant level is stabilizing?
Could be. I wouldnt worry about it unless the level continues to drop over time.
Checked the car out when I got home yesterday. Oil looked fine coming out from the dipstick. I took it for another drive around town and got on it a few times. Power seems fine, AFR looked good, and everything else seemed normal. Not that this matters but for reference, I'm running 18-19 lbs through a GT35R. I put a mark on the coolant overflow tank to note the level before I ran the car. The level was higher when I got home; good thing which means the coolant system is working like it should. I checked the level this morning and it returned to where I originally marked it yesterday which is also good.

I'm going to perform a compression test either today or later in the week just for confirmation. I have plans to put on a built head but I would like to wait until next spring.
I would say you do not have any issues.
I did a compression test yesterday. I let the car get up to temp. then pulled the injector harness to keep them from firing. Made sure to keep the throttle body open. I got the following numbers:
1) 150
2) 155
3) -
4) 158 - 160

Unfortunately, I couldn't test cylinder three as my external wastegate is in the way of getting to the spark plug and I didn't have enough time to remove it. I'm pretty happy with the numbers. Thoughts?

Edit: I did not remove all spark plugs. I took one out at a time. My understanding is that removing all of them is just to allow the motor to turn over easier but I'd like everyone's thoughts on this too.
Removing all plugs to do the test is ideal, but remember absolute psi numbers arent that important. It is consistent numbers for all cyls. CR, cam used, cam timing, etc can significantly alter the actual numbers.
Jeff K Wrote:Removing all plugs to do the test is ideal, but remember absolute psi numbers arent that important. It is consistent numbers for all cyls. CR, cam used, cam timing, etc can significantly alter the actual numbers.

Thank you Jeff. I obviously don't have numbers for cylinder 3 but I would say 1,2, 4 are nice and consistent
(08-09-2019, 03:32 PM)John B Wrote: [ -> ]
Jeff K Wrote:Removing all plugs to do the test is ideal, but remember absolute psi numbers arent that important. It is consistent numbers for all cyls. CR, cam used, cam timing, etc can significantly alter the actual numbers.

Thank you Jeff. I obviously don't have numbers for cylinder 3 but I would say 1,2, 4 are nice and consistent

Sorry, but it’s not a complete test. And, ideally, you should run the test twice for each cylinder.

Yes, the numbers for 1,2 and 4 are great. But according to previous posts here (and my own experience), for some reason the head gasket seems to blow between 3 and 4 on the TCs.

Now, you obviously don’t have a blown head gasket, at least between the cylinders. But if it was me, I would have nagging doubt about how cylinder 3 was reading—not that there is any cause for concern. I’d just eventually be overcome with curiosity.

I would also be curious—were I you—as to what readings I would be getting if I put a tiny amount of engine oil in the cylinders. It’s a good way to check the condition of the rings, and why not if you are checking the compression anyway?