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Coolant temp problem (kinda long)

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The Avengence

20+ Year Contributor
348
1
Jan 15, 2003
Milwaukee, Wisconsin
i did some searching here on tuners and correct me if im wrong, but ive discovered that the coolant temp on a 1g usually runs between 195 and 210. now heres the problem... i just got a jdm engine put in my car, and ive been driving it since last wednesday (the 9th) and today while i was sitting in my driveway checkin out some stuff on my datalogger i noticed that the coolant temp was steadily goin up, so i sat there and i watched it. it went from 196 to 223 in about 5-6 minutes. when it hit 223 i decided it was probably time to make it cool down so i revved up the engine a lil bit and held it at 2500rpm until the temp fell back to 197. now before you say "check all the cooling stuff like rad., t-stat, etc.," you should know that ALL of it is brand new (like "last week wednesday" new)... the only thing that isnt new is the coolant overflow bottle. However i noticed i was leaking coolant from one of the lines goin to the turbo, but i had that tightened down earlier today. anyone got any ideas what this can be?

Thanks
Josh
 
Sounds like there is air is the system. Meaning there's not enough coolant. When the car is just sitting idling, the water pump isn't spinning fast enough to get past the air pocket. When you rev it, it moves the coolant along. Let the car idle, with the heat on, and the radiator cap open. If the coolant isn't already low, it should drop when the thermostat opens. Then top it off and you should be good to go. A small leak will cause the same problem once the coolant gets low enough.

Also, the fan is supposed to kick on at 210. If it's not, most likely the sensor in the bottom of the radiator is no good, that's very common. Or a bad fan relay. If the fan doesn't come on at 210, pull the plug off the sensor (bottom of radiator, passenger side) and jump it with something. If the fan turns on, you know the sensor is no good. If it doesn't you'll have to diagnosis it from there.
 
turbolover2 said:
Sounds like there is air is the system. Meaning there's not enough coolant. When the car is just sitting idling, the water pump isn't spinning fast enough to get past the air pocket. When you rev it, it moves the coolant along.
Naw. DSMs don't hold air. If any's left, they'll purge themselves in the first five minutes of running.
Also, the fan is supposed to kick on at 210. If it's not, most likely the sensor in the bottom of the radiator is no good, that's very common.
The fan sensor is on the thermostat housing.

If you haven't, replace the radiator cap.

Do the fans ever come on while idling?
 
Defiant said:
Naw. DSMs don't hold air. If any's left, they'll purge themselves in the first five minutes of running.

Ok. But regardless, if you don't let the car idle long enough to know that the air has purged after filling the coolant up, the coolant will be too low, and you will run hot at low RPM. Basically, if the coolant level is low, but not reeeeally low, the car will be ok if driving but overheat at idle.



The fan sensor is on the thermostat housing.

If you haven't, replace the radiator cap.

Do the fans ever come on while idling?

I'm not sure on a 2G, that may be the case. But on a 1G the sensor that turns the fan on is definitely in the radiator.
 
Defiant said:
Do the fans ever come on while idling?

Yeah fans come on when they should, they run for a bit then shut off and then theyre back on again like 30sec to a minute later.

But yeah i put a small amount of coolant in so that it went up to the "full" line and i was just out in the garage for like a half hour just sitting in the car with it idling and this time it didnt get over 201, so i dont know what the hell is going on. i guess ill have to check it again tomorrow. hopefully the problem fixed itself but i know how unlikely that is with a dsm :cry:

Thanks for the help guys
Josh
 
The Avengence said:
Yeah fans come on when they should, they run for a bit then shut off and then theyre back on again like 30sec to a minute later.

But yeah i put a small amount of coolant in so that it went up to the "full" line and i was just out in the garage for like a half hour just sitting in the car with it idling and this time it didnt get over 201, so i dont know what the hell is going on. i guess ill have to check it again tomorrow. hopefully the problem fixed itself but i know how unlikely that is with a dsm :cry:
Thanks for the help guys
Josh

You need to check the engine "radiator" cap on top of the thermostat housing. Just filling the overflow bottle to the line will not solve the problem. Fill the engine to the top and then see if that doesn't solve your problem. Don't worry if the overflow bottle gets full but do keep checking that it doesn't get empty. Make sure you always have heat coming out of the heater when it's on and the engine is at least showing warm for that is a good sign that the water level has gotten too low if you loose your heater.

The radiator cap is designed to hold pressure to around 15 lbs but allows for it to syphon from the overflow back into the engine. This is usually enough to keep it topped up but as things age it's not always reliable so keep your eye on it until you are sure it's behaving normal.

Cheers,
GTM
 
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