It also doesn't help it is 110° outside as well

It isn't just the temperature, it's the pressure. If you motor is healthy and it's not generating pressure to the coolant the only cause for boiling water in the expansion tank is a broken radiator cap that can't hold the pressure.

Yeah I'm not sure an oversized tank is the solution, because I've never seen that needed on high hp cars before. But iono

In fact just this Friday I beat on a turbo miata with a TSE rad and stock overflow, in 90-100F heat, and nothing boiled over or overflowed.

This could also be a sign of air in the system - Air is way more effected by thermal expansion than liquids, giving you the exact side effects you're having.

That being said, if the previous expansion tank was suited to an OEM sized cooling system and you've increased capacity. It might not be a bad idea to go bigger as a lot can be said about properly matching expansion tanks, but I'd first work on properly burping the car. I ended up purchasing an AIRLIFT Coolant Bleeder system, it creates vacuum in the system and then sucks the coolant into the negative pressure areas. That being said, I run a rear mount radiator and an electric water pump so it might be overkill for you but it would certainly cross that off your list. I don't mind sending it out to you, just get it back to me in working order.

Edit: There is absolutely something to be said about the importance of your radiator cap and coolant mixture. You can increase the boiling point of water by nearly 50 degrees by simply pressurizing it properly. Furthermore you can increase boiling point by running the proper mixture of antifreeze. I'm sure we've all heard "run water, it runs cooler" - this is true water will dissipate heat more quickly but it will also boil sooner. (Note: some of us are required to run just water depending on where you're running your car, coolant is slippery)

For every additional pound your cap is rated for the boiling of point of the mixture raises 3 degrees. If you had plain water in your cooling system with a 15 pound pressure cap water would boil at 257 degrees. If you had a 50/50 mix of antifreeze and water the coolant would boil at 265 degrees with the same cap rating.

Bottom line - if you're boiling before your car is overheating you have at least one of the following happening: Air in the system or a weak rad cap. I had both of these issues, along with an expansion tank that was smaller than OEM on a system with nearly double the capacity.

Yeah, did you bleed it with the big yellow funnel? Getting all the air out of the TSE rad can be tricky.

--Ian

<p></p><p>+1 for a vacuum purge system. Suck, Fill, Drive.</p><p>&nbsp;</p>

A big tank is a load of bull shit.

If there's boiling water in the line going to the tank, there's going to be boiling water in that line whether its 1 cup or 1 million gallons on the other side of the line.

Stop dicking around and pressure test the system, if it holds pressure to whatever your cap is rated to, something else is going on. If not, it's the cap.

Not complete bullshit but I agree with you. I'm sure he has air in the system and doesn't need a bigger tank. To determine the proper expansion/overflow size you would take the total volume of coolant, and multiply it by the expansion rate of the mix you're using. Then make your tank bigger than that. The reason the large overflow solves his problem for now is related to the air expanding in the system, thus increasing the expansion rate of his mixture.

I've seen cars with 4-5x the power a turbo miata makes, and cooling systems with twice more capacity, and still they didn't run a bigger tank than stock (which also happens to be not bigger than a stock miata tank).

So yeah, to beat the dead horse for the last time: burp the system. If that doesn't help then pressure test.

Standard radiator cap for a ~2004 Dodge 2500 Cummins. Available at any auto parts store.

e: I've been racing N/A and turbo cars on our radiator for 6 years. I have never once boiled the system over or seen any need for a larger coolant overflow tank. Consider my extensive experience in varied applications with this specific radiator before you go and design a part that isn't going to fix the problem you have

Looks like the radiator cap was indeed the issue. no boiling, gurgling, or overflowing the overflow tank now. Temps hold steady at 192º when moving now even with it being 105º outside.

Followed Revlimiter's very detailed advice and managed to get all the air out of the system after several several thermostat cycles and with the aid of some very tall truck jack stands to get the front up as high as I could.

Also decided to put a 13" SPAL fan in place of my OEM fan. Bryan obliged and sent me a package...I had to leave the bakery from laughing so hard at the name on the package.

https://www.miataturbo.net/attachmen...ine=1439400152

Also finally got a real coolant and oil temp gauge from VDO. Going to see if I can fit them in the factory coolant temp and oil pressure gauge spots.

Decided to get a new exhaust manifold gasket as well. I reused my old one as my flawed reasoning thought that it hadn't been on the head long so I would be ok using it again.

I'm slowly trying to eliminate variables on my slower spool. 4k rpms is just too slow. No leaks at the manifold to turbo vband, downpipe, or EWG. Going to play around with a MBC to see if something is up with my solenoid. We'll see, slowly but surely I'll figure it out.

So you took off the head because of a faulty radiator cap?

Well only partially did my stupidity apply to that logic. Mostly I was concerned it was necessary due to my head studs only being torqued to 30 ft lbs.

But looking back, I'm mildly annoyed at myself for ignoring the radiator cap. Lesson learned I guess.

Gotta remember I'm no pro at all this stuff. I'm figuring it out as I go. Throughout the entire car build I never once touched the engine.

plus it gave him a reason to polish the inside of his engine

Polishing the rods and crank will reduce stress risers thus making them stronger, plus the oil won't cling to them thus lightning the rotating assembly. Polishing the inside of the block itself will help the oil return to the pan too.

Do it Jeff, polish ALLTHETHINGS inside of the block. :likecat:

There is actually a guy on youtubez that does this /\
Successfully.
And then coats it in some anti-friction coating or something.
He must be Jeff's grandfather

Also if I recall you had oil in your coolant? I'd say between that and your stud torque (with mileage), a head gasket was in order.

+1. Oil in coolant = HG.

Localized boiling due to inadequate radiator cap, low stud torque and dyno tuning likely caused the HG failure.

It's all good and we're one step closer to pictures of a fully-polished interior on a BP.

Guys don't jinx the block now....I'm sure I'd enjoy polishing all the internals, but the only items I have yet been forced to "fix" are the block, transmission, and differential and suspension. Let's leave those happily untouched!

Bryan/Hornet bring up a good point, the oil in the coolant proved the HG job was not all for naught.

Vlad are you talking about that red rubber like coating the miata guy on youtube coated his block/head with?

yeah