i know there is like a million overheating threads and i've been through them all!!!!

[hulkster_s13]

I am getting really fed up with this motor. I had some overheating issues before this and i thought i resolved it. so heres the situation, I rebuilt this motor,
stock bottom end new OEM rings and rods and 2 new pistons,arp rod bolts and ACL bearings/washers. new oil pump and new water pump,block was checked and its straight. also cleaned.freeze plugs replaced. I'm listing everything I've done so you guys can help me out.
For the head I got it cleaned and decked and I measured and got new shims for valves. New supertech valve seals. stock cams. new OEM gaskets for everything,and i mean everything.HG is a Cosworth 1.1. stock intake manifold, stock injectors, stock EX manifold S15 turbo
For cooling i got alum. koyo radiator,FAL 220 dual pullers,PBM swirl pot, 1.1 bar cap, OEM nissan thermostat.PBM EVDM to watch water temp and oil pressure.water temp sensor is located on the outlet side sandwiched between the head and the water neck(waterneck sensor adapter)
Now at idle temp rises normally and just keeps rising, on the PBM sensor it went all the way to 238F with fans on. On the cluster it was at H. Thats the highest i got it. now i wont let it go above 220f before i shut down. ive been through 3 new thermos, 3 new rad caps and 2 new water pumps, and this bitch is still overheating.
So i thought maybe i had a leak somewhere, i did a leakdown test cylinder 1-3 had 3%, cylinder 4 had 4%. so I'm all good in that department.
next i pressure tested the coolant system. pressurized to 20psi and found 1 leak. took care of that. Ran the car thinking that leak was somehow sucking in air, nope still overheats. then i did the block leak test the chemical one that detects exhaust gasses in coolant, fluid is blue then changes to yellow if it detects gasses, no color change. even used my breath on it to make sure it works and it did change to yellow.
So that is where I'm currently at. please help with suggestions. If i missed something let me know, also i blled it every step of the way

[e1_griego]

Sender properly grounded? Tried a different gauge?

Also, put a clutch fan back in :)

[hulkster_s13]

I don't have a clutch fan or shroud. It's grounded properly.

[S14DB]

When do the fans come on?

[hulkster_s13]

I got it set at 185f.

[bkuhl]

fully bled the system?

[hulkster_s13]

every step of the way. i have a swirl pot also so that helps. i was thinking airlock but ive drained and re-filled alot. any time i drained something that has to do with cooling i bled it. my koyo has a dummy cap and the swirl pot has the 1.1 cap. routing of hoses is this,
bottom of swirl pot to lower hose, middle hose to koyo,top hose to bleeder screw on water outlet and the very top to overflow reservoir

[hulkster_s13]

It also doesn't seem like the tstat is opening. Bottom radiAtor hose is always cold. But I tested it before I put it in And it opens at 174f. Radiator is really hot at the top and cold at the bottom but without the tstat whole radiator would get hot. But still run hot. I had the radiator tested and they told me it's fine. Also ran a hose through it and it flowed fine. Flushed the block out for 30 min (15 min on each side) and no debris came out.

[JuMPiiN]

Not to sound dumb, but did you loosen the bleeder screw on the intake ? My KA thermostat wouldn't open so I ran the car without one for a while because it would always overheat. I replaced the thermostat a good 10 times before I properly bled the system. If it isn't bled correctly the thermostat won't open. Atleast that's how it was in my case.

[hulkster_s13]

Sorry forgot to mention but this is a Sr. I don't have a bleeder screw anymore. I tapped it and put a hose fitting to go to my swirl pot

[KiLLeR2001]

How does the car run? When driving it when its in the process of overheating to you notice a drop in performance?

[Sileighty_85]

Gotta ask since you didnt say

Fans wired properly for pulling?

[hulkster_s13]

Car runs great idle is 850 steady and fans are wired correctly and I don't drive the car on the street because of the heating issue. Motor has never seen more than 3500 rpm due to motor break in. Motor has only 14 miles on it so far. If a water passage was clogged how would I flush it out and even if the fans were wired backwards wouldn't that still be sufficient cooling at idle? And why would the bottom half of the radiator be so cold. Thermo is installed correct jiggle valve up. Should I route my swirl pot differently? I'm also not running a heater and hoses

[KiLLeR2001]

Is the swirl pot elevated above the radiator? It needs to be above the bleeder screw on the water neck as well. Have you thought about trying another radiator?

[daryl337]

I'm interested in your fuel and ignition settings.

If, as you are expressing, your fan works, your 3 new thermos, 3 new rad caps and 2 new water pumps did not fix the concerns, and you are certain you do not have any air pockets or restrictions in your cooling system, then your engine should not have a problem over heating unless the combustion chamber temperatures are abnormally high, or your engine is recieving poor lubrication.



How is oil pressure? Did you measure bearing clearances, or simply order an oversized set?

Do you have an EGT to see what exhaust temps are looking like? Having no hydrocarbons is a good sign and helps eliminate a cracked head or block.

You mentioned the inlet hose is cold, and the outlet hose is hot, this leads me to believe you have a restriction in your cooling system somewhere. Either the restriction is in the radiator, or it is on the outlet side of your cooling system. Does your water pump make any noises while running? I know they are new pumps, so noise may appear minimal, but a strange gurgling/swirling/vibration style noise from the pump can indicate that it is cavitating. You may want to put a stethoscope on it to see if you hear anything of that nature.

Do you or a friend have a laser thermometer? That might also give you clues.

[roboticnissan]

Your positive your headgasket is on the right way?

[daryl337]

I hope you arent insinuating that he has the headgasket on backwards or something of that nature.

Spacial and shape recognition is one of the earliest developments of our upper brain function, and im pretty sure a 3 year old child could figure out how to line up the headgasket properly, especially considering that the timing cover cut out only has 1 orientation.

If you were referring to proper installation via torque specs, etc... his hydrocarbon tests seem to be coming up as a negative.

-edit-
changed my verbage in regards to headgasket orientation

[HOOCH]

if the top of your rad is hot and bottom is cold that means its not working right to a point, as long as the system is pressurized it should flow just fine! Had this problem on my '64 Plymouth pro-street and i replaced heads & gaskets, new fan and water pump and it still ran hot so i put a stock radiator back in and now she runs 185 all day at the track! ( and the bad radiator was an aftermarket aluminum)

[hulkster_s13]

killer-swirl pot is above the radiator i got it mounted on the strut tower so it just touches the hood when closed

daryl-the 3 thermos that i went through were all brand new but the first 2 one was from orielys and it was stuck closed, the one from napa stuck closed and the final one is from nissan that i tested before putting in and it works, i tested the first two after i took them out.
for the caps i had the one from my KA radiator on the koyo but it did not seal properly so it kept overflowing to the reservoir. nismo cap i had didnt seal also. now i got the 1.1 bar PBM cap. and the water pumps was changed just as a 'what if' precaution both are brand new nissan pumps. i also tried a used OEM SR radiator and it overheated faster.
oil pressure is good cold start up is around 74psi when temps rise the oil will thin out to about 11psi at 220f water temp. i dont let the motor run past that temp. bearings was done by my machinist all per FSM.
no funny noises from water pump. i do have a laser thermo and i checked temps in front of the thermo and behind, there is about 50f difference 120f front and 170-180f. seems like the thermo isnt opening again.maybe airlocked behind the thermo thats why it's not opening? should i drill holes in the thermo? would that help the airlock behind the thermo? i still have the jiggle valve in there. and i dont have EGT sensor.

roboticnissan-shit i put it on inside out!

HG is on correct with arp head studs torqued down following FSM

[hulkster_s13]

I also jacked my car up from the drivers side with 2 jacks like it's sidewheeling in hopes that if there was an airlock by the thermo it would move but nothing changed, a few little bubbles came up but nothing really major

[KiLLeR2001]

Have you tried running it without the thermo? if it still overheats at the same rate with thermo removed then you could rule that out.

[hulkster_s13]

Yea I did that with oem radiator and koyo. What do you think about drilling like 2 extra holes next to the jiggle valve in the thermo?also I have clear lines for the swirl pot does anyone know if the water flowing will visible? Like if there is a air bubble in the line is it supposed to shoot fast through the line? My air bubbles seem to just settle right before entering the pot? I would assume that the water pump would push it out. If thats the case. Which would lead me to believe that the water passage might be blocked even though I flushed it.

[daryl337]

You should have circulation. Your water pump should "stir" the fluid so that it is constantly circulating. In regards to air bubbles, the bubbles will always try to remain at the highest point they can reach. If your hose set up has a high spot, that will trap bubbles.

I wonder if you have air bubbles trapped in the head. I've forgotten the stock specs for the thermostat opening point, but you generally will have it somewhat warmer on the engine side of the thermostat than on the hose side, after all the thermostat acts as a gateway to allow the cooler fluid into the engine.


Killer made a good point about removing the thermostat entirely, if you still have overheating issues then you more than likely have a cooling system restriction problem.

What are the temps like for the coolant coming out of the head?

Im fairly confident that you have some sort of restriction / air pocket problem.

[JuMPiiN]

Remove the thermostat completely. The throttle response will blow but you won't overheat any more.

[hulkster_s13]

I did remove the thermo and ran it with the koyo and the stock radiator it still got hot. The coolant head temp gets all the way up to 220, I don't run beyond that. I'm thinking restriction/airlock also, that's why I was wondering about drilling 2 extra holes in the thermo to allow some fluid to pass through in hopes of maybe displacing the air that I think is behind the themo keeping it closed. If that doesn't work I guess I got to take the head off and inspect both block passages and head passages. I don't want to do that.

[daryl337]

If the thermostat is removed you should be able to jack up the front of the vehicle, remove the radiator cap, and start squeezing hoses like crazy to move coolant. If your radiator is full, the movement of the coolant should try to force the bubbles into the radiator.


If that doesnt work, You can turn the car on with the radiator cap off, and run at idle while also squeezing hoses. Of course you can only really do this for a short time.

[Kiro1968]

With or without the thermostat, and jacking the car up on its side is not going to help remove air pockets. The engine needs to be at approximately a 30 degree angle so just jack the front end of your car up with the radiator cap open. Start the car and let it warm up and when its warm turn on the heater to full blast and have it switch to internal circulation. The coolant system doesn't just travel inside the block only, don't forget the heat exchanger or heater core under the dash. You have to bleed the entire system. You can create air pockets when filling the system up if the car is level.

[hulkster_s13]

I'm not running heater. Post 13. I throughly understand how the coolant system works. I've built many motors for people and the time I do it for myself something gets fucked up. I've never had an overheating issue with my other SRs. Jacking the car on the side was a hope, maybe it would knock it loose.

[S14DB]

Put the front end on stands and get this:
Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive (http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0)

[hulkster_s13]

Put the front end on stands and get this:
Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive (http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0)

Got that. I bought it about 2 weeks ago. That's one reason I think there is blockages in coolant passages

[hulkster_s13]

So I think I got it. I think it was airlocked. So today I took out my thermo and drilled 2 3/16 holes, one on each side of the jiggle valve and I also cut the jiggle valve off. Ran the car for about 20-30 min. No overheating. Also the thermo did open, idle temp got up to 184f then dropped to around 160f. I'll report back tomorrow after I go on a test run to see if it overhears. But I'm pretty confident that the airlock was the problem. With the 2 holes in the thermo allowed enough fluid in to push all the air out. Air bubbles came out fast in the lines of the swirl pot.