Rb25, Heat just builds and builds, what a suprise!

[GhostofAkina]

Hey there dudes,
I know there are only a few hundred RB "Hey my shit over heats threads" but I seriously need some ideas other than, "did you bleed it correctly???, derr". I'm going crazy here, my shit has been running great other than constantly having to watch the temps for the past year and drive with the heat on most times.

My issue: Engine temps slowly raise even while driving tame, it takes about 15-20 mins of stop and go traffic on a hot day to get this baby up past 210 and get that lovely boiling sound in the heater hoses and back of the head. Basically any coolant house near the back of the motor. Its the worst in the bottom heater core and turbo line. If I do a WOT pull it will raise the temps to above 210 almost instantly. WOT up a hill? Worse. I can drive it on the highway like a grandfather for about an hour and a half with little worries so that kind of has me wanting to try another radiator but who knows.

My set-up: S1 Rb25DET
New waterpump and timing belt 3 months ago
Chasebays tucked radiator
2 11in fans, one pulling, one pushing. both are set up correctly, blowing and spinning in the correct directions. Run off of relays from the ECU. First one turns on at 165F I think and the second at 185F.
Nismo low temp thermostat
Top radiator hose has a tall fill neck to collect air bubbles
Swirl pot to bleed out said bubbles
Fitting in lower radiator hose for swirl pot
Diverter plates on top to direct air to radiator and I also made one for the bottom to direct air upward into radiator instead of down and out.
stock turbo



I have flushed the system 3 times or so with prestone or whatever brand cleaner. Used a spill free funnel to bleed the system (even though it shouldn't matter now with the swirl pot and overflow tank). Its tuned so the tune isn't the issue. I have pressure tested the system, fixed any leaks that I had found. I have had my coolant system tested for exhaust gases and none were found. I autocross and can get away with driving without a hood, that helps a bit. Only for a while though, the temps still rise and are hard to get back down.

Well lets hear some ideas, maybe there is something I am completely overlooking. Maybe my radiator sucks, I don't know, I haven't heard much about the chasebays tucked radiators. Maybe my CFMs from the fans suck but they are the biggest fans I can fit on my radiator.
Opinions and suggestions wanted!

[mmakam2]

what radiator are you running?

i run in 100F temps all day in traffic with A/C on and i dont oeverheat, but i have a nice fat aftermarket radiator

also you can throw in a lower temp thermostat, 160-175ish i think is good

[fliprayzin240sx]

Originally Posted by mmakam2

what radiator are you running?

i run in 100F temps all day in traffic with A/C on and i dont oeverheat, but i have a nice fat aftermarket radiator

also you can throw in a lower temp thermostat, 160-175ish i think is good

100F? Do you even know the fucking difference between F and C? Shits not even up to temp, you're fucking up the engine if its that cold all day.

Back to the OP, what gauge are you using to verify it is overheating?

[mmakam2]

100f ambient tard...

[fliprayzin240sx]

Originally Posted by mmakam2

100f ambient tard...

Ambient on what? Your fucking AC Temp? 100* F is fucking 38* C, the fucking nismo thermo doesnt even open till 67* C...tard.

Why would anything else really matter in his case since his shit is pegging pass 210* F?

[mmakam2]

Originally Posted by fliprayzin240sx

Ambient on what? Your fucking AC Temp? 100* F is fucking 38* C, the fucking nismo thermo doesnt even open till 67* C...tard.

your making yourself look even worse bro just chill the fuck out.

im talking about the ambient air temperature outside in the world, how is that so hard to understand.

I know when a thermostat opens, thats why i recommend one that opens 160-175F, which is roughly 67C.

edit. so this guy doesnt shit a brick, 67C is exactly 152F

[mmakam2]

to the OP:

you should pull your thermostat and make sure its opening at the correct time by putting it in a pot of water with a thermometer, or just try a different one.

I personally think your radiator is not big enough.

[EccentricBro]

Originally Posted by fliprayzin240sx

Ambient on what? Your fucking AC Temp? 100* F is fucking 38* C, the fucking nismo thermo doesnt even open till 67* C...tard.

Why would anything else really matter in his case since his shit is pegging pass 210* F?

hahahaha i'm dying. "in 100f" aka the car is in 100f. but that wasn't obvious enough...he tells you ambient...do you know what ambient means? hahahahahaha i can't tell if you're trolling or what...it's hilarious how you are getting so mad about how right you are

[GhostofAkina]

LOL, oh Zilvia.net, you.
In my OP I stated that I have a Nismo lowtemp thermo and a Chase bays tucked radiator.


It doesn't seem to be an issue with the thermo opening incorrectly because the pressure on the top and bottom rad hoses seem to be normal although that can't be totally ruled out since I haven't tested it. It may very well be the radiator not being able to keep up but if that were the case I wouldn't be getting these air bubbles and gurgles in colder temps when the car doesn't even get the chance to heat up too high. I have a Haltech ECU so I am reading the temps straight from my laptop. Any other questions or suggestions are very welcome. I am trying to figure this out without just throwing money and parts at it and crossing my fingers. Next chance I get I am going to get it leak down tested. I have already compression tested and its got great compression across all cylinders.

[BoredEE]

Make sure your mechanical timing is correct, count the number of teeth between cams.

You might have already done this:Check base electrical timing, check compression, check leak down, Pressure test the coolant system.

The fan setup sounds questionable, a photo will help to show how the fans are setup. Whats the CFM ratings of them?


I've thought of buying that radiator so I can rock out the mechanical fan. Why are you still running electrics? Try the mechanical one if you still have it.

Also is the water pump new, or newish?

[GhostofAkina]

Borede, Timing is definitely correct, it would be pretty hard to mess up the timing on an RB25. The ECU timing is also correct, I have a haltech ECU so you lock the timing and make sure that it is calibrated correctly. I mentioned I already checked compression, its great. Pressurized the coolant system but I want to do it again when I get a chance just to make sure there aren't any sneaky leaks or spots that air could be entering the system. The fans are supposed to pull 1200cfm each if I recall correctly. One is pushing the other pulling, not much more to say about it, they are both spinning the correct way and have the blades on in the correct orientation. If you put your hand behind the fans you can feel they are moving air and its hot so the heat is getting exchanged. I am not sure where the hell my stock fan went but it had a broken blade anyway so it wouldn't help much. The water pump is brand new OEM.

[mmakam2]

hey whered u get ur swirlpot by the way? i want to get one

[fliprayzin240sx]

My apologies to mmakam...I need to get off my bathsalt medication. Just for his situation, being 100* is the least of his worries since he's having issue of the engine overheating fairly quick.

Back to the OP: Did you make sure the jiggle valve on the thermo is at the 12 oclock? If for some reason you're not sure and you decide to check, might as well pop the jiggle valve off. Also, how do you have your swirl pot routed? Are you only using one of the inlet nipple into your swirl pot? I'm only seeing one line going into the upper swirl pot and I'm assuming that's coming from the custom neck. Also, that neck has a pass thru radiator cap right? I'm just not ready to write off the chaserbay radiator since its a dual pass rad, I just dont see it heat soaking that fast.

This is how mine is setted up...

[GhostofAkina]

Yes to jiggle valve, it's 12 o'clock.
Yeah, the swirl pot only has the line coming from the fill neck which has a seal cap on it. I have been planning on teeing the remaining line into the turbo feed line, it is one of the worst for bubbling when it's hot.

MMkamm, I got the swirl pot cheap off of ebay I think, it is a circuit sports one. Poweredbymax.net also has them.

[fliprayzin240sx]

Tap the 2nd swirl pot line to the bleeder screw on the Intake manifold. I know its pretty close to where you got the other one tapped to the filler neck on the upper radiator hose but its worth a shot. Also, try bleeding it somemore by jacking up the front end as high as you can and try to massage the upper rad hose with the heater on full blast. Maybe there's still air in the system.

If that doesnt work, I'd consider going back to the stock clutch fan with a fan shroud on it first before I opt to replace the radiator. Atleast with that radiator, you have more space between the engine and the radiator support.

[GhostofAkina]

I don't have the bleeder screw, I am using a Greddy manifold and never put that on. I also already said in a reply to you that I don't know where the stock fan is and even if I did it had a broken blade.
The one thing I asked was for people to not suggest bleeding the system as I have already done this more times than I can remember. The entire point of the swirl pot is for it to bleed the system of air. I would T the second nipple into the rear of the block before I would tap into where the bleeder screw would be, there is no point for two spots tapped so close to each other in the cooling.

Maybe I should have said what I think my issues may stem from right off the bat. I think the two most likely sources of the air bubbles that cause my motor to get hot are either a very small leak in the headgasket or a very sneaky leak in a coolant connection. As in, tight enough to not leak a noticable amount of coolant but just loose enough to pull in air.
I do not feel there is air trapped, I feel air keeps finding its way into the system from somewhere. Which is why I have had the cooling system checked for exhaust gases next chance I get I am going to leak down test it.

I appreciate the thought though. Like I have already said I want to figure this out without throwing money at it until I know for sure what the cause of the bubbles/gurgling/raising temps are. If I haven't by this winter I am probably just going to do a headgasket any way just to see if coolant passages in the block or head are blocked with debris.

[40craz]

Not to jack but I'm doing my swap in my s13 and wanted to knw wht fans to go with so I don't run into the same shit lol

[S12 Drifter]

original poster what was the previous life of the motor? was it a track motor at some point in it's life? how are the coolant jackets? are they rusty? what head gasket are you using? and stock studs are ARP studs? have you jacked the front end of the car up to properly bleed it?

[funktown240]

I would recheck your base timing, I have a RB25 swap and a Haltech platimum pro ECU also. My CAS is rotated to one side to get 15 degrees of timing at idle. I have had problems with high coolant temps in the past and they were mainly cause of the timing being retarded. If you have the stock ECU you can set base timing and go from there. You could also put the mechanical clutch fan back on since you have a tucked radiator.

I run a clutch fan with a stock S13 radiator in Texas heat without any overheating issues whatsoever.

[OutToWinPAHC]

I run 120-150F with a nismo Tstat, clutch fan, PBM swirl pot and koyo rad in a R33, clutch fan is the way to go IMO

[Yellow4g63]

180's all day even when it's hotter than 100 outside in traffic. Clutch fan and ebay swirl pot.

[GhostofAkina]

Originally Posted by S12 Drifter

original poster what was the previous life of the motor? was it a track motor at some point in it's life? how are the coolant jackets? are they rusty? what head gasket are you using? and stock studs are ARP studs? have you jacked the front end of the car up to properly bleed it?

I don't know what the previous life is, probably sat in an r33 in a junkyard or something. I ordered it and put it in a year and half ago. I have no clue what the coolant jackets look like since I have never taken the head off but I can only assume they were super rusty, I flushed the system three times, until the coolant looked clean. Stock head bolts. Seriously enough with the bleeding shit, I know how to bleed a cooling system.

[LayNLow]

The radiator is probably too small for the heat a RB puts out.

[GhostofAkina]

Originally Posted by funktown240

I would recheck your base timing, I have a RB25 swap and a Haltech platimum pro ECU also. My CAS is rotated to one side to get 15 degrees of timing at idle. I have had problems with high coolant temps in the past and they were mainly cause of the timing being retarded. If you have the stock ECU you can set base timing and go from there. You could also put the mechanical clutch fan back on since you have a tucked radiator.

I run a clutch fan with a stock S13 radiator in Texas heat without any overheating issues whatsoever.

Maybe you know this, maybe not, but with the Haltech you lock the timing on the ECU to whatever you want. 10 degrees, 0 degrees, 15 degrees, 3 degrees, anything, and you make sure that's what your number one cylinder is firing at ensuring that the ECU is calibrated. I don't know why you would ever put the stock ECU back in to time it. Once calibrated if I notice its retarded, which it isn't it drives great other than bubbles in the system, timing would then be adjusted in the timing tables. Again, I don't know where my clutch fan is and if I did it wouldn't help, there is a broken blade on it.

My shit runs fine, here is the dynograph and it runs just like it did when it rolled off the dyno. Its at 12.5lbs.

[S14DB]

Get one of these and check you hot and cold pipe temps. Then check across the radiator.
Infrared Thermometer with Laser Targeting, Non-Contact

Where are you reading the temp right now? What kind of sensor?

[GhostofAkina]

The oem RB25 two wire ECU coolant temp sensor and I read it off my laptop. The sensor itself is in the top coolant neck off the Greddy manifold.
Yes, I do need one of those heat guns.

[S14DB]

Just to be sure. You got a new sensor when you did the swap. Not using the sensor that came with the motorset?

[supersayianjim]

how

about

changing your heater core??

i brought a new one from ebay for super cheap before i nuked my head gasket.

[funktown240]

HP is low for 12.5 psi but whatever. Your fans are now blowing enough air through the radiator, find your clutch fan and replace the blades. I had to do this since my blade assembly was cracked. Buy one off of Ebay for under $40 NI3112105 | eBay

[fliprayzin240sx]

Originally Posted by GhostofAkina

I don't have the bleeder screw, I am using a Greddy manifold and never put that on. I also already said in a reply to you that I don't know where the stock fan is and even if I did it had a broken blade.
The one thing I asked was for people to not suggest bleeding the system as I have already done this more times than I can remember. The entire point of the swirl pot is for it to bleed the system of air. I would T the second nipple into the rear of the block before I would tap into where the bleeder screw would be, there is no point for two spots tapped so close to each other in the cooling.

Maybe I should have said what I think my issues may stem from right off the bat. I think the two most likely sources of the air bubbles that cause my motor to get hot are either a very small leak in the headgasket or a very sneaky leak in a coolant connection. As in, tight enough to not leak a noticable amount of coolant but just loose enough to pull in air.
I do not feel there is air trapped, I feel air keeps finding its way into the system from somewhere. Which is why I have had the cooling system checked for exhaust gases next chance I get I am going to leak down test it.

I appreciate the thought though. Like I have already said I want to figure this out without throwing money at it until I know for sure what the cause of the bubbles/gurgling/raising temps are. If I haven't by this winter I am probably just going to do a headgasket any way just to see if coolant passages in the block or head are blocked with debris.

Well you're not loosing coolant correct? If you have a leak or even air getting in thru your HG, you'd be loosing some coolant over time. My RB looses some over time but my guess is that the coolant just isnt coming back into the swirl pot from the overflow, when the engine cools down.

As far as debris...shit is probably rusted pretty bad. Depending on where the engine came from in Japan, some places dont believe in running coolant. My engine's from oki so they almost always just runs straight freaking tap water. I had to clean out the damn water jackets of rust when I replaced the HG before I swapped it in.