Boiling coolant but temp gauges check out normal

[IwantMKIII]

Basically what the title says. I've been having a lot of issues with the rad leaking, long story, but its now fixed. What I'm coming across now is boiling coolant. I'd say its mixed at least 35-40% coolant and the rest distilled. I can hear it boiling in the block and steam coming out the res yet both temp gauges check out normal, 160* F at the hose coming from the head to the heater core and below half at the water neck. Pressure will not build in the system. Not really sure what to make of this. Ever since I switched back to this radiator (its from a 1jz) from the broken mishimoto's ive been experiencing this problem, unless I simply didn't notice it before, but I doubt it. My guess is, because its not building pressure, its affecting what temp the water boils, but just want to get other input. Also, I have been losing coolant but my guess is because its turning into steam.

 

[Poodles]

Correct, without pressure, it will boil. You have a leak somewhere.

 

[IwantMKIII]

strange, I can't find any leaks, especially ones that would be large enough to eliminate pressure build up. I'll look again of course.

 

[Poodles]

That's the problem, all it needs to be is a pinhole to release pressure and screw the system.

 

[IwantMKIII]

pinhole leaks are easy to find most of the time cause they whistle or spray most of the time, my guess is im looking for a steady drip which can be difficult at times. whats worse is im driving 4.5 hrs this weekend to WV so i need to find it quick.

 

[S.A. supra]

you don't think it could be a bhg?

 

[Poodles]

That is a possibility, but I hate waving that flag so soon. It could be as simple as crap around the radiator cap or a tired cap...

 

[JonnyZ(Socal)]

Pressure test the radiator cap or just buy a new one and return it if the cap isn't the problem! Having a faulty radiator cap can cause the fluid to boil. For every lb. of pressure in the system it raises the boiling point of the coolant by 3* i believe! So if you have no pressure then of course it will boil! And make sure you get a cap that holds the proper amount of pressure because you dont want the coolant too high or low!

 

[IwantMKIII]

Cap is new, I have suspicions it's the rad, both mishimotos before they blew built pressure no problem even after my recent (may, 6k miles ago) headgasket change (not because the previous was bad, change rear timing gasket, it blew, new hks stopper was used).

 

[Poodles]

Plastic end tanks? Did you seal the sensor hole well enough?

 

[S.A. supra]

That is a possibility, but I hate waving that flag so soon. It could be as simple as crap around the radiator cap or a tired cap...

I had the same symptoms you are having. The boiling sound coming from the block (the hot side by the turbo), steam coming out the reservoir, and the guages reading normal. it was a really small bhg. Cylinder 6 and lead to the water jacket. As long as the car was running it was OK but shortly after I would cut the engine. It would start with the boiling sound and blow steam out the reservoir. Not trying to be dooms day or anything, but I would do a quick compression check just to eliminate the bhg.

 

[IwantMKIII]

Plastic end tanks and sensor was sealed with a custom cut bolt, however threads were slightly stripped so I filled it with epoxy with the bolt and what little threads remained

 

[hvyman]

Maybe try getting a 50/50 mix. I have to add some water here and there because my mix is not 50/50. No leaks and never had any.

Straight water will boil in the block even if there is no leaks.

 

[IwantMKIII]

Will try coolant is just so expensive these days it's tough to waste if there is a leak somehwere

---------- Post added at 11:27 AM ---------- Previous post was at 11:25 AM ----------

Mishimoto has their prototype being sent to them so if they need a tester which I'm sure they will I'll be the first to have it, hopefully that will fix my issues

 

[3p141592654]

Has the system been pressure tested?

There are two factory rad caps, and they are not interchangeable. The 89+ cap is smaller and will leak if put on most aftermarket rads, and pre 89 rads.

 

[IwantMKIII]

Actually it's a 1j rad with a new cap

 

[IwantMKIII]

So i'm thinking more and more its the rad cap. Here's why, the car running does not boil over, but off it suddenly starts. Now what i've been noticing is even when its steaming out the res there is still no pressure in the top rad hose at all, which means its going right past the rad cap when it happens. Does this idea seem flawed?

 

[mkiii racer x]

Did u retorque the head after u drove it xxx amount of miles?

 

[grimreaper]

I always bring my radiator pressure tester with the adapter and test the caps before I walk out of the store. Saved me a trip or two more then once before! if the store has a rental tool program, use theirs while your there.

 

[IwantMKIII]

Yes I re-torqued and yea, i need to test that cap, never have tested a cap before.