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ricekikr
02-22-2015, 02:40 AM
Does an AEB have a coolant internal pressure release valve or is it the cap itself, just like how radiator caps work?

Cause i've cracked two coolant flange (where the sensor locks, 3 ports total).

Seerlah
02-22-2015, 04:42 AM
No pressure relief, but an overflow.

gmx
02-22-2015, 06:13 AM
Cap itself.

ricekikr
02-22-2015, 10:02 AM
No pressure relief, but an overflow.


Cap itself.

So like a radiator cap? So just bad luck with the flanges. Oem flange warped because hardpipe was misaligned. Replaced with OEM (but looked fake, markings were lighter than my stock flange), cracked one sensor socket. Replaced with Dorman both sensors cracked which is odd, because if one cracked, there would be little pressure.

Cracked = sensor/plug, flew away.

Are the coolant caps known to fail? (ie not release pressure). Cause most radiator caps fail in a way that they don't hold pressure.

Seerlah
02-22-2015, 10:17 AM
No, the cap has no pressure relief. If you wanted to relieve pressure, you would need to open it slowly (not too fast, or just imagine boiling coolant burning you). You control the vapor release. At this point, the pressure will bring coolant with it. Since there is an overflow, it won't come out where the cap/reservoir threads are. It would overflow underneath that (look at the design of the reservoir next time you get a chance).

ricekikr
02-22-2015, 10:31 AM
Ahh ok. I always thought the little round holes were a sort of pressure relief valve.

So what can cause enough pressure to crack the flanges (not warp but crack). The sensors/plugs, were locked normally, then added some zipties on top to help hold sensors. These were big zipties (roughly 10mm wide).

Everytime the flange cracked was at 30+psi and 6k+rpm

One theory was lifting headbolts at high boost (35psi), but there are no other symptoms, (no smoke, no mayo oil, no loss of power at low boost (23psi)). The only other symptom is an apparent loss of hp at high boost (around 100whp accdg to calculated hp). The calculated HP has been pretty consistent for the past couple of years (same road, same maths), butt dyno says i haven't lost 100whp, feels slower but still makes power.

I haven't done a comp/leak test yet.

Edit: The last flange (oem but looks fake) lasted around 3k miles, Dorman flange around another 3k miles. No warping both cracked where the sensor locks in.

Seerlah
02-22-2015, 10:36 AM
You hit it on the nail. It's not the head bolts. Most experience this with the Victor Reinz gasket. Elring is preferred for high boost apps and what b6 people found fixed it. Add APR head bolts for good measure.

ricekikr
02-22-2015, 10:50 AM
You hit it on the nail. It's not the head bolts. Most experience this with the Victor Reinz gasket. Elring is preferred for high boost apps and what b6 people found fixed it. Add APR head bolts for good measure.

Didn't think this was common since some people run 40+psi on stock bolts.

I've replaced the headbolts (various mundane reasons, like one leaking valve seal) several times already. Should've gone with ARP from the very beginning lol.

So Reinz bolts + Elring gasket will work fine for high boost. Cause right now I'm on elring bolts + reinz hg

Thanks for input. Time to do further tests to confirm.

ricekikr
02-24-2015, 06:53 AM
No, the cap has no pressure relief. If you wanted to relieve pressure, you would need to open it slowly (not too fast, or just imagine boiling coolant burning you). You control the vapor release. At this point, the pressure will bring coolant with it. Since there is an overflow, it won't come out where the cap/reservoir threads are. It would overflow underneath that (look at the design of the reservoir next time you get a chance).
Cap looks like it has a bypass. The upper portion doesn't seal to the coolant tank.

http://tapatalk.imageshack.com/v2/15/02/24/011b0d7c3c58b30741a51e3fb3b6a844.jpg

Avant Nate
02-24-2015, 08:10 AM
I'm pretty sure the cap is your pressure release valve, but what it's rated for I don't know. You can maually release the pressure by unscrewing it. But a failing cap, in my case, caused me to lose coolant. So if your coolant level drops off, and especially if your coolant boils, check your cap.

Seerlah
02-24-2015, 08:25 AM
My cap does not look like that. It is nothing but a cap on mine.

Mad Cow
02-24-2015, 08:37 AM
My cap does not look like that. It is nothing but a cap on mine.

That's weird, every cap I've seen has the pressure relief. I actually had to replace mine because it was opening too early,

BaseDrifter
02-24-2015, 10:42 AM
Yeah I've never seen a cap that wasn't a pressure relief valve either. Here's ECS' description of the cap, just to throw this out there.


The coolant expansion tank cap maintains an elevated cooling system pressure to raise the boiling point of the liquid coolant, while venting excessive pressure to atmosphere.

Seerlah
02-24-2015, 11:49 AM
Just looked and I do have one. Never noticed. I had a reservoir burst on me before so I assumed I didn't have one. I relieved the pressure by slowly loosening the cap, letting it vent, and overflow take care of the coolant.