B serious

Out with the (c)old. In with the new.




Heat blows nice and hot.

Had a chance to try out the Billman coolant bleed and it worked better than the factory procedure I've done in the past.

Thanks for all the help!

Hopefully the slight bend in the water neck is not the cause of this. The old cap's gaskets and springs seemed just fine.

Billman250

After a nice ride, and the car is good and hot, pop the hood with the engine running, and mark the level in the res with a marker.

Shut it down and re-check in the morning. The level should drop. If it doesn't, it is pulling air into the rad instead of coolant, and you will be low again.

B serious

Will do!

To note...when I pulled the old cap off, it made a suction noise. Strange because the "suction" plunger on the cap doesn't seem difficult to move or anything.

The car always had OEM coolant. So...no silt or buildup anywhere.

B serious

So...long story short, the problem seems to repeat itself

I found this little bastard was hiding itself by facing toward the back of the car.



The reservoir thread seems a little ovalised too.

So...for now, I've duct taped it and said the phrase "that'll hold er". So it would probably hold up to any test of durability.


To be safe, a new reservoir, cap, hoses, and gasket are en route from Honda.

I think the cracked cap may have been the issue the whole time. It allowed expansion AND leaking of the coolant in the tank. I can't see how this would prevent suction back into the radiator though. The hose is dunked into the fluid...so...

Idk. Maybe someone knows something I don't.

Billman250

You are on the wrong track.

That split in the res cap has no effect on the radiators ability to draw coolant back into itself.

The upper seal/fit of the radiator cap is the problem.

B serious

Thanks for chiming in

Here are the factors...maybe you can make something out of all this.

The rad cap is brand Koyo new from an authorised dealer.

After completing the bleed procedure in the posts above, I may have overfilled the reservoir thinking that a lot of it should get drawn back in. So every time I drove it and it got hot, some coolant would slosh and come out of the cap. A miscalculation on my side.

The heat was always hot.

A weird thing is that whenever I went to check the radiator level by opening the rad cap (car was totally cooled off...like 6 or 7hrs after driving it at least), the radiator would be BURSTING with coolant. Taking the rad cap off always resulted in some coolant pushing out of the radiator neck.

I remedied my previously overfilled reservoir by draining it til it was just above the "min" line when fully cold.

I drove it again and the heat was still hot.

I parked it for a few days until today.

Today, the heat was lukewarm...then hot..then cold as I drove it. Ripping it caused more heat to come out.

Sure enough, when I got it home, I opened the bleeder near the VC. TONS of air came out.

I re-did the bleed procedure and found the cracked reservoir cap.

I'm in agreement that the reservoir cap has no effect on sucking fluid back into the radiator.

BUT...the cracked res cap can also explain all the splashed coolant at the track day. And it may explain the large amount of coolant expansion (??)

The radiator cap doesn't externally leak.

I'm going to try go go back to square 1.

Refill the reservoir with a new reservoir cap to just under the MAX line.

Make sure the coolant is bled.

Take it thru a few drives and see if the bleeder hisses air in a week or two.

Thoughts?

Chris_Lum

Regardless if the rad cap is the cause or not, I would try a different radiator cap. I had a brand new Koyo radiator and brand new Koyo cap on my DC2 and under 20 min of sustained 85-95mph highway driving, I found that the cap had leaked. That one experience alone made me lose faith in their cap. I swapped it for a Spoon cap and no issues ever since (both street and track).

B serious

After the "reset" I described above, it seems to be going OK.

I'll keep monitoring it. Thanks for the tip on the Spoon cap though!