*** incorrect expansion pressure cap being supplied by Honda ***

[latzke]

I wonder if this is why mine blew at the track too. I had just replaced the cap with this part as part of a radiator change just before NSXPO...

Yep, we were BHG (blown head gasket) buddies at that NSXPO. For YEARS I chalked it up to NA1 engines having weak head gaskets...and now regret that in title of my post about head gaskets I blamed/shamed/named the gaskets as the NSX's "Achilles heel" - when all along it was probably that stupid cap. I recall you having another explanation for yours, which you now may be questioning.

I've pinged some of the NSXPO HPDE guys (Titanium Dave, Bruce M) about adding an item in the HPDE tech sheet specifically to look for the black OEM cap. Figure that simple change could raise awareness and maybe save a one or a few folks from similar fate. (Have not heard back from them.)

I've also been commenting on BAT auctions where I see the black cap in engine bay photos. To raise awareness and get buyers to replace that cap.

 

[Honcho]

Yep, we were BHG (blown head gasket) buddies at that NSXPO. For YEARS I chalked it up to NA1 engines having weak head gaskets...and now regret that in title of my post about head gaskets I blamed/shamed/named the gaskets as the NSX's "Achilles heel" - when all along it was probably that stupid cap. I recall you having another explanation for yours, which you now may be questioning.

I've pinged some of the NSXPO HPDE guys (Titanium Dave, Bruce M) about adding an item in the HPDE tech sheet specifically to look for the black OEM cap. Figure that simple change could raise awareness and maybe save a one or a few folks from similar fate. (Have not heard back from them.)

Yeah, the explanation at the time was a loose bleed screw on the radiator and at the main coolant hose in the engine bay (Shad discovered them in the pits at the track!). That may have still been the cause, but I can't help but wonder if a bad cap played a part too. [MENTION=31359]jazzmann[/MENTION] if you're reading this- I would replace that cap with the SoS one if Ben hasn't done it already!

I agree screening for this cap or at lest using a pressure tester on the driver's existing cap should be part of a tech sheet for the track days.

 

[nis350]

Just curious if the cap was the culprit for the damage of the head gasket, did the coolant temp go into the red on the gauge?

Yep, we were BHG (blown head gasket) buddies at that NSXPO. For YEARS I chalked it up to NA1 engines having weak head gaskets...and now regret that in title of my post about head gaskets I blamed/shamed/named the gaskets as the NSX's "Achilles heel" - when all along it was probably that stupid cap. I recall you having another explanation for yours, which you now may be questioning.

I've pinged some of the NSXPO HPDE guys (Titanium Dave, Bruce M) about adding an item in the HPDE tech sheet specifically to look for the black OEM cap. Figure that simple change could raise awareness and maybe save a one or a few folks from similar fate. (Have not heard back from them.)

 

[Honcho]

Just curious if the cap was the culprit for the damage of the head gasket, did the coolant temp go into the red on the gauge?

In my case, the gauge went straight to red on the back straight and the entire coolant bottle emptied out in about 4 seconds. Pulled into the pits and Shad thought there might be an air bubble, so he refilled coolant and bled all of the points. The radiator plug and the main hose bleed screw in the engine bay were completely loose- like not tightened at all. Tons of air came out. He gave me a worried look and recommended I get a block gas test, which I did the next day and it indicated a blown head gasket. In my engine, the heads were lifting under heavy load, but at normal driving the car was totally fine and passed a compression test. Because the heads lifted evenly, neither the block or the heads were warped. I got lucky, I suppose. Looking back, the cap may have contributed to this. But, whether the overheat occurred due to the cap or all of the air being sucked into the system from the loose bleed screws, we'll never know...

 

[nis350]

I have the old OEM cap with black and yellow in the center, new Stant after market just bought and the black OEM I replaced a few years ago. I'm not technical, but they all look the same and have similar measurements.
[MENTION=18194]Honcho[/MENTION], I imagine the coolant temp would move up slower than just 4 seconds if the cap was the problem?

 

[jazzmann]

Yeah, the explanation at the time was a loose bleed screw on the radiator and at the main coolant hose in the engine bay (Shad discovered them in the pits at the track!). That may have still been the cause, but I can't help but wonder if a bad cap played a part too. @jazzmann if you're reading this- I would replace that cap with the SoS one if Ben hasn't done it already!

I agree screening for this cap or at lest using a pressure tester on the driver's existing cap should be part of a tech sheet for the track days.

Thanks Honcho, I'll check with Ben. I know he replaced the coolant tank, prolly has the OEM cap. But will verify and replace it w/ SOS if so.

 

[Honcho]

I have the old OEM cap with black and yellow in the center, new Stant after market just bought and the black OEM I replaced a few years ago. I'm not technical, but they all look the same and have similar measurements.
[MENTION=18194]Honcho[/MENTION], I imagine the coolant temp would move up slower than just 4 seconds if the cap was the problem?

Not necessarily. The problem with the defective caps is that they cannot maintain the proper pressure (1.1 bar) for the coolant to avoid boiling inside the engine at high load/heat states. If the coolant boils/create steam pockets, it can rupture the head gaskets, which will allow engine compression gases into the coolant, which will blow it all out of your bottle.

 

[nis350]

thanks for the explanation. would this abrupt condition also occur under normal driving condition or we'll see the coolant temp. rises slowly?

Not necessarily. The problem with the defective caps is that they cannot maintain the proper pressure (1.1 bar) for the coolant to avoid boiling inside the engine at high load/heat states. If the coolant boils/create steam pockets, it can rupture the head gaskets, which will allow engine compression gases into the coolant, which will blow it all out of your bottle.

 

[Honcho]

thanks for the explanation. would this abrupt condition also occur under normal driving condition or we'll see the coolant temp. rises slowly?

Probably not under normal conditions because the engine never really gets hot enough. In that case, you might see the needle moving slowly higher.