Newbie observations on KA24DE Head design & coolant flow path

[djsilver]

New to the KA but not new to motors. Recently became the owner of a '93 hatch w/ 194k miles & a headgasket leak into the coolant system. Ran great but blew bubbles in the coolant system. I did a pressure test to find out which cylinder was guilty and found all four leaking. Pulled the head for a redo and I have these observations;

1. The coolant flow path design sucks. Putting the thermostat on the suction side of the water pump is a bad idea. Throttling flow on the suction side of a pump is never a good idea. It invites pump cavitation. This design probably contributes to the difficulty of getting air out of the cooling system and the general sensitivity of the KA24DE to overheating.

2. The coolant passage down the center of the head does not appear to have any supports cast into the back side of the deck surface that separates the combustion chambers. The head on mine (which had been overheated) was low in just that area between 1-2, 2-3 & 3-4, but was not warped diagonally or end-to-end. Is this the typical failure mode on the KA head? Any of your turbo guys try drilling through the top of the center coolant passage and adding support? I would think it's worth consideration. The critical design issue would be doing it without creating hot spots.

[djsilver]

Bump! I'd think that with so many threads in these forums starting with "blown headgasket!", this might be of interest. No?

[hannibal]

Good thoughts, but way over my head personally.

Ive heard stories of having to bleed the cooling system 5 or 6 times to get all the air out. You provide a good explanation.

[sanioll]

i did full system flush couple weeks ago. There are some steps to fill the system.

I will do a full DIY write with pics. No one follows the directions properly, and air gets trapped in the system. With one single fill, i haven't had any overheating, bubbling problems and I've been driven it very hard. Average temps last week was about 95 F and still no overheating at all.

[MarkEmark]

Bump! I'd think that with so many threads in these forums starting with "blown headgasket!", this might be of interest. No?

Hahah, exactly, I think this is far too technical for the vast majority of people browsing the KA-T section. But yeah, as long as people follow directions when flushing the system it won't overheat. Mine stays at 178 degrees rock solid on the highway at 90 mph (4000 rpm in fifth gear) on an 85 degree day. Koyo radiator and new water pump. The highest it got today on a 50 mile ride was 194 degrees with the AC on, going like 30 mph up a hill (damn traffic). Not bad.

[klattr1]

i would think that most of the blown headgasket people dont realize they are turbocharging a previously NA setup which is mapped with aggressive timing.

so they throw on a turbo kit and SAFC and boost to 11-13 psi and air fuel ratios are rock solid but dont realize they might be running too much timing.

but thats what i think.

[HolyShiznit]

^^^ I am with Klatt on this one.

BTW: Which higher HP KA's have suffered from these "crappy" head and coolant design problems? Cause I can't think of a single one. Orion has never had a problem and he road races/auto-x's/drag races. Also I agree that 90% of people never properly flush and fill the coolant correctly. Personally I have never had a problem and I have changed my coolant fluid 4 times and had the whole system apart twice on my boosted application. Stock bottom end 14.7psi, not one head gasket/overheating problem. It's all in the tuning.

[Aaron_9349]

I would also agree with this ^^^

My first go at the tuboing the KA ended up with the overheating problem. For the longest time I thought it was the head gasket not sealing, since it was a copper one, but i think it was a combination of this and that there was still air in the coolant system. I was way too excited to get the car running to pay proper attention to the flush. So, yeah my excitement and stupidity resulted in the loss of a lot of time and money.

Yet, I do find the observations interesting. I don't have any experiance with dealing with this area however (other than the overheating aspect), yet I would be interested to hear more on if anyone has actually tried these reinformcment ideas out.

[Aaron_9349]

hehe... I said Tuboing