devlman

iTrader: (13)

I was driving my FD tonight and the car started idling at 2k pretty much out of nowhere. i had just had a cat put on last week and thought maybe the Power FC was adjusting (since it was doing the oscillating idle thing earlier) to a change perceived at a sensor. But then I thought maybe it was trying to cool the car off (could be wrong about this, but doesn't the factory ECU rev the engine up when very hot to promote coolant circ? not sure if the Apex PFC does it).

when i parked it, i popped the hood and heard a precolating/boiling sound from the coolant hoses, which were abnormally hot. first time i'd noticed this ever happening. Also noticed fans were off, but I had done the full-time fan mod about a month ago (when I also flushed the whole cooling system) and they're usually ALWAYS on. After a few seconds, one of the weak little hoses coming off the AST (stock, plastic) and running into a nipple connector that returns to the overflow reservoir blew off and started spewing coolant everywhere. It did this on two separate occasions (like vomiting) within about five minutes, and it was very obvious when it stopped each time (like a valve closing).

I plugged the hose back in and let it sit for an hour and cool off in the cold chicago air then fired it up again. idled right at 750, fans came on as normal and all seemed fine. i drove home (15 miles, temp showed 83 all the way) and noticed the fans had gone off sometime during the drive, but the idle was still fine and temp holding at 83.

I have a huge Greddy intercooler and aluminum radiator and my temp gauge was only reading in the 90s, 100 at most at the worst point (but this is still noticeably higher than usual—it's normally locked at 83-85, even when idling). still, something doesn't add up. before i did the fan mod, the car would inch toward the 110 degree mark on hot summer days and i never had any issues like this, so it seems odd that something would pop at 90-100.

the car has 49,000 original miles and a new engine 3,000 ago. it's totally stock except for the reliability mods and a Greddy intake. my peak knock reading on the PFC is usually about 35. I'm running base maps on the PFC and was going to LM-1 tune it this weekend (it's been in the car about 3 weeks now).

i'm trying to narrow the trouble down so i can have an efficient weekend of pinpointing the trouble if there is any. thermostat? freak accident? bad ground on the fans? anyone have a good place to start? sorry this is so long.

jon

skunks

the high rev is probally due to the dash pot.

the precolating/boiling sound from the coolant hoses is pretty normal as far as most fd's are concerned. the little hose comming off is not normal however, try zip tying it on or using a small worm clamp.

you should have done the fan mod so you cna control all 3 fan speeds 100% of the time, when car is on, fans should be at least on low unless your in subzero temps.

are you getting any coolant out your exhuast? have you gotten all the airbubbles out of your coolant? what coolant ratio are you running?

devlman

iTrader: (13)

I may revisit the fan mod to get control over all speeds, but i'm still not sure why they're coming on and off when I've got them wired in full-time. I may have to check the wiring to make sure i've got it going to full-time power.

coolant is pretty high water content. close to 50-50. no coolant in exhaust.

David Beale

Could be several things. Failing fan relay. Sticking thermostat. You may have developed a vacuum leak in one of the caps which will cause the car to pump coolant into the overflow tank and not suck it back. Eventually it overfills the overflow tank and coolant boils in the engine because there is a large air bubble in it (allowing the coolant to expand - thus boil - if there is a small or no air space it can't expand without overpressuring the system, in other words the pressure in the system prevents it from boiling). The air bubble could be large enough that the temp. sensor is no longer immersed in coolant, so the fans will not start. Ususally, the low coolant sensor trips first, though.

rynberg

The first thing to do is to replace the radiator (AST) cap. It's a cheap thing to do and will eliminate that from your troubleshooting.

Obviously, you have some fault with the fan-mod wiring, or a problem with the fan relays. Troubleshoot that.

Once you've gotten the fans running, if you still have problems, the thermostat would be the next item on the list.

Good luck.

devlman

iTrader: (13)

thanks for the help so far, all.

i've actually completely disconnected the four fan relays for the mod. after reading different ways people have done it, i decided to let them run all the time and just hook 'em right up to acc power. could this be a problem? didn't think so, but i'll admit i'm not sure.

i'm not sure i'm getting any coolant back into the overflow tank at all, actually. when i filled the system, i went almost all the way to the top of the radiator cap and kept filling until i no longer got the low coolant light/alarm. it's been fine for a month. maybe it is an air bubble and the pressure it created blew the hose. if it's not backflowing into the reservoir, i suppose the coolant would have nowhere to go when the system expands...