Built sr starts to overheat under boost
 

Hi guys, trying to figure out the reason why my sr coolant temp will rise from 190 f cruising to up to 235f(reading on upper neck) when boosting.it will go up almost instantly. I can take it easy amd drive for hours without a problem but as soon as I step on it it will rise the temp 25 degrees and take a while to start going down.
My setup
Koyo rad
Alum shroud
Isis fans
Nismo thermo
Fans on from the get go

Things I checked:
Water pump is pumping
Thermo is opening
Did a leak chemical test and came up good.
Going to do a compression test in the morning
Seems to use a lil bit of coolant after a 70 mile drive

What else could I check? So wierd I cam drive car all day long and be within 190-210 but when boosting....

What is your afr under boost?

Around 10.5-11
I'm using haltech
Aem wideband.

Hmm that's just about perfect. What temp gauge? It weird that it moves that much instantly, makes me thing the gauge is fucked

If it uses up coolant id say you have some kind of a leak. May be your radiator cap is not holding pressure or something like that. Im assuming the car was tuned? May be something in the tune didnt account for higher summer temps if the tune was done in colder temps? Idk just throwing in my two cents lol.

Or a bad headgasket, only leaks under boost and pushes extra heat into your coolant

I might have lied a lil bout instantly. But with in a minute will be going up there. Is a prosport water temp and using the stance water neck adapter.rad cap is 1.1 bar and overflow tank lvl stay the same. I could take it to get checked out for leaks but not sure how that affects raising temp so fast. Is 230 still safe to drive?

190 cruising is too high in the first place.

I'm cruising around the low 170s.

Check your thermostat. Upgrade to a Nismo that opens up at 155*. Will help a lot.

What fans?

Only other thing i can think of is stuck open thermostat. When i didnt have one my temps would rise quick because the water just kept circulating without having a chance to cool down the water in the radiator.

Might actually be the headgasket. It makes sense too. Losing coolant, overheating under boost. Do a compression and leakdown test and you'll know for sure

That was my thought initially but i think that thing would have been a paperweight by now. Plus the oil and water probably would have mixed by now.

Not if it's cracked just enough to leak only under boost. It would just push compression into the coolant

I do have a nismo thermostat and I can tell at idle with cap off when is close and after it opens, I did the leakdown test and apparently is good. Fluid never turned yellow.
Using isis fans
Well I will update in the morning when I do the compression test to confirm gasket. And will retorque the arp studs.
Also using cometic hg

No oil on coolant and drained oil and is not milky brown color. This is a frwshly built engine with no more than 800 miles

What coolant you running? Distilled water or 50/50?

That doesn't explain 190 temps at cruising.

I put 50/50 but with so much draining testing and bleeding who knows. I've been adding water instead. In the morning while cruising is more like 180f 85-90 afternoons like 190-200. And after i step on it 220-230

I really hope compression test comes ok.
Think Ing of ditching the isis fans for altima?

190 isn't very hot. Especially in the summer on a turbo car. To me that's just about perfect temperature.

Your fans are fine. Especially with that big rad. If you were overheating in traffic or low speed then yea i'd say fans, but since it's only under boost you have something else going on

What's your boost pressure?

Temp will raise more on stop after boost too. Lets say I boosted and raised temp to 210 if I stop it will raise somewhere in 220-225. When running at 10 psi is not that bad but when I set it a 18psi it gets bad.
Forgot to mention I have ac condensor on the car and a third fan for the condensor. Should I try to hook it up and have all 3 and see what happens?

Lots of shit coming lol.
Did you retorque the head studs? The head could be lifting under boost if the studs are loose. I believe you have to tighten them in stages, if you just slammed them down once and that's it then i'd bet they are not tight.
What bumper are you running? It could be as simple as not enough airflow to the rad. With the intercooler and condenser in front of it you need to get as much air to it as possible. That's why you see some people cutting holes in their bumper.
Make sure the fins on your condenser aren't all bent up. If its beat up with a lot of bent fins it will stop a substantial amount of airflow to the rad. Get a comb and straighten them out
Make sure your rad hose(s) aren't collapsing under acceleration.
Under drive pulley's are the devil, ditch them if you have them.

Just throwing shit out there for you to check.

Thanks lol. Well if fans are a issue and have a pusher hell why not try it. Just saying lol. Longblock was assembled by machine shop so I'm supposing they did it right. I will double check that in the morning.and thanks ill check the fins etc.
Using s14 jdm kouki front bumper. Jdm grill

Wait are your current fans pull or pushers?

Pull. I double checked the are in the right direction

Fak. That would have been the easy fix lol.

In the right direction as in pushing air in the right direction? If you have polarity switched and they are spinning backwards that would be funny as hell but yeah as someone said easy fix lol. Trust me ive seen people do that a few times and they were competent mechanics just made a simple mistake lol.

fans shouldnt be on during cruising more than about 15mph. they actually slow down the air flow by blocking the faster moving air. fans are only supposed to run at stops and at slower speeds where the air flow isnt sufficient over the radiator. 30 bucks gets you an electronic fan switch/thermostat for those fans. thats what i run on my altima fans with my sr. other than that, check that t-cap. it does sound likes its opening under boost.

Yeah fans are pulling air away from rad towards engine.





Haltech have outputs for fans. My fans were setup at 190f but changed to 100 while I solve this issue. T-cap?

i meant the r-cap. what pressure cap are you running?

I personally would not drive at 230...

I think you have a leak somewhere. The system functions under pressure; which is what helps keep the coolant from boiling. Build heat by boosting, pressure escapes out of a weak point in the system (boils), temperature rises.

Check the coolant feed/return lines & crush washers (if applicable) on the turbine... It could be tight enough to keep the coolant in under cruise; but not enough to keep it in under boost (heat). To add insult to injury, if it's a leak like I described, only steam will escape and/or the coolant will boil off on the center section of the turbine... so you'll never really see a puddle or drips.

The thermostat is there to keep the coolant to within a specified heat range. Continuously flowing coolant thru the radiator will not cause an overheat; and will definitely not cause the temperature to rise quickly... It will cause the coolant to warm up slowly, then 'overcool' when driving. The reason it opens/closes is to keep it warm (thermo closes, coolant heats up)- but not allow it to get TOO hot.


I think it's a leak at the turbine. If it were the cap, I think there would be coolant boiling out of the reservoir.

I hear a lot of stories about burping the system etc. To this day, I have still never had to burp my coolant system- just fill her up; drive and service as needed until it doesn't need anymore- never overheated.

One last 'totally dumb' thing to check- and I promise I am not trying to insult anyone's intelligence...

since you've been doing all this servicing & flushing... maybe check the drain plug...