92 KA24DE Overheating Plague

[kielan92]

My name is Kie, This is my first post.

I have have been plagued with this problem for a year and a half now, I have replaced everything you can imagine and have taken it to multiple shops and yet I can still not find the problem. It overheats randomly, there is no order or rhythm. Heres the list of why has been done and when:

Pulled an engine off craigslist to put in 92 hatch, It over heated also. long story short i blew the radiator, ran it low on oil and possible scored the cylinder walls with my pistons. Or at least that whats the shop said. SO i built the hell out of the engine after.

Current engine:

JE 11.1 Forged piston
new gaskets
new bearings
new seals
Stock shot peened rods
Polished crank
Dynamically balanced down to 1 gram-ish
Bored .5
About a grand of head work (everything I could do to it)
bowl blend to run 91 octane
248,232 cams ( didn't have money for BC stage 3)
walbro 255 pump
z32 MAF
550cc injector
Enthalpy Tune

Bolt ons and cooling system:
DC 4-2-1 Headers
Greddy Exhaust
AEM Pop charger
Mizu Radiator
High end new water pump
new Nismo thermo stat 143 F
new silicone hoses
new clutch fan
No AC so I hot wired electric fan to toggle switch


Heres whats going on now, the engine was fine during brake in. No over heating ran great. about 2000 miles later, it over heated randomly after going over a speed bump at 2000 rpm about. Ive bled it about 20 times with the car up, screw open, cap off, heater on full and half way. Ive pressure tested the system (with a crap bicycle pump but it lost about 4psi an hour). Ive had it re tuned, I switch to a colder plug and that took away the pinging and the ECU pulling timing. but still over heats. I also only have 17 Pounds of vacuum. my compression across all four is 280/300 depending on whether it wants to max out my compression tester. usually a 10 PSi difference between cylinders. oils is perfect color, no signs of coolant. i even checked under a light. no white smoke, no loss of coolant. even drove it after 2 months of not being started and it was fine. no hydro lock, no loss of coolant. SO I am beginning to wonder what it could be? intake leak? coolant leak in heater core? how much of a leak is needed to let air in? maybe i got a bad mizu radiator? imperfection in block or head? Ive had master mechanics tell me they have no idea and I am out of money and can't keep trying to fix it. I must sell if I can't fix it.

ANy help would be great Zilvia

[soryu]

when overheating does the gauge go all the way up to the H?
does it come back down after a couple of minutes or hours?
do you hear any bubbleing coming from the hoses or overflow tank?
what about replacing the temp sensor?

[kielan92]

I have after market gauges so I can tell you it goes up to about 260. it climes slow to about 210 then just shoots to 260. It comes down slowly sometimes and sometimes it take a couple minutes. I pull over some time but and sometimes i speed up to air cool it or try it come down.
When it comes down, it usually comes down fast, like a bubble passing almost. But i doubt its air. and sum times it take a while to get it to go down. but freeway driving cools it off fine. and it over heats even when its 50 degrees out. no bubbling or boiling over. I had G 05 mixed 50/50 and it won't boil over. sometimes the over flow rises a lot but i don't ever hear it or see it bubbling. and i have a glow shift after market temp sensor.

[kielan92]

also, at 32 psi of pressure testing I have about 6 leaks in the intake cooling system, but at 22 psi I have none. The leaks are back thermo house, inner coolant hose of intake, 2 intake freeze plugs and both heater nipples in fire wall. but with my cap at 19 psi, i should not need to test any more then 22, and I have no leaks at 22. and we all know that tearing apart our intakes is a b****, so i rather not just do it for fun. unless someone thinks that that could be the problem. i just don't know how visible leaks are at 22 psi.