jarrettjp
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Intermediate
Joined: May 2005
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From: dallas n.c.
jarrettjp
hello all! i know there are a lot of posts about overheating,but i'm going to post another one.my 90 coupe had been running hot for about a week,so i tried to purge the air out of the radiator by taking the cap off and bringing the coolant to hot.when i did this the coolant flowed out the top and it will not go into the overflow tank.well i took the car to a radiator shop and they removed the radiator,put a new thermostat in and put two gallons of antifreeze in.said the cap was good.it still runs hot(very close ti the hash marks on the guage) this is sitting in traffic.i meant to say that they cleaned the radiator.but why will the coolant not go into the overflow?i took the hose loose and blew water through it thinking it could be stopped up,but that didn't work.could it be a senser?my low coolant light doesn't work. sorry about the long post---thanks-------jp
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Joined: Jun 2004
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From: WI
Well the rad cap hole is large so coolant would flow out there first. Pressure from the cap being on would cause the coolant to go in the smaller opening to the overflow. Hashmarks, is there a specific temp number? If the shop didn't fix the problem you brought it there for, I'd want a refund or the problem fixed round 2. Though round 2 might not be worth it! 
Melting Slicks
Joined: May 2005
Posts: 2,730
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From: Atoka Oklahoma
St. Jude Donor 06
c4's naturally run hot, my 93 just got flushed and radiator cleaned a few weeks ago and i haven't seen it over 210. 198-205 seems normal running temp.
the overflow gets coolant and returns coolant back in the system as needed. with mine at idle i can very slowly add coolant and it will fill the over flow. sounds like your tube is plugged. also at an idle my resovoir is full, then idle up a few hundred rpm and the res. is very low, let off throttle real fast and the coolant will run out.
have you checked the fan or fans to make they are working properly? if coolant sensor is inop i would replace it. cheaper then new motor.
keep us posted to your findings
the overflow gets coolant and returns coolant back in the system as needed. with mine at idle i can very slowly add coolant and it will fill the over flow. sounds like your tube is plugged. also at an idle my resovoir is full, then idle up a few hundred rpm and the res. is very low, let off throttle real fast and the coolant will run out.
have you checked the fan or fans to make they are working properly? if coolant sensor is inop i would replace it. cheaper then new motor.
keep us posted to your findings
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Joined: May 2005
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From: dallas n.c.
thanks for your replys. where is the coolant sensor? on the recovery tank where the overflow comes in is a black rubber thing that is clamped on the tank nipple.when i put water pressure on it from the other end the water would come out in little spurts.i guess that whole overflw line is one piece.the fans work when the ac is on,i don't know if they come on any other time.i wonder if i can replace the cap with a 16 lb. one the original is a 17 lb. i don't think there is any gaskets blown because the oil and the coolant are clear.the temp gage has 160 on the top and 260 on the bottom.today,while sitting in a traffic back up for 20 minutes it climbed to about 256 or 257.---thanks ---jp
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Joined: Feb 2003
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From: Kingman AZ
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Cruise-In VIII
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16
Coolant lever sensor on my 87 is just below the cap and the upper tranny line. Be careful not to break the clips when you remove it. Also when you remove it be prepared for antifreeze to come out. Have something there to catch it.
I just finished a hands-on C4 class with Chris Petris (one of our gurus). He says that your temp guage should not go over 230 F. If it does so then you have other problems. The biggest problem with overheating is the trash and leaf buildup between the radiator and the AC condensor which sits in front of it. There is a 2" or so space there that fills up with highway crud. I cleaned mine a couple of weeks ago and found about a 3" depth of leaves. This effectively reduced my radiator size by about 10%.
There should be some posts here on how to do this. Do a tech search. This is probably your problem and is relatively easy to fix.
I just finished a hands-on C4 class with Chris Petris (one of our gurus). He says that your temp guage should not go over 230 F. If it does so then you have other problems. The biggest problem with overheating is the trash and leaf buildup between the radiator and the AC condensor which sits in front of it. There is a 2" or so space there that fills up with highway crud. I cleaned mine a couple of weeks ago and found about a 3" depth of leaves. This effectively reduced my radiator size by about 10%.
There should be some posts here on how to do this. Do a tech search. This is probably your problem and is relatively easy to fix.
Melting Slicks
Joined: May 2005
Posts: 2,730
Likes: 1
From: Atoka Oklahoma
St. Jude Donor 06
Originally Posted by jarrettjp
thanks for your replys. where is the coolant sensor? on the recovery tank where the overflow comes in is a black rubber thing that is clamped on the tank nipple.when i put water pressure on it from the other end the water would come out in little spurts.i guess that whole overflw line is one piece.the fans work when the ac is on,i don't know if they come on any other time.i wonder if i can replace the cap with a 16 lb. one the original is a 17 lb. i don't think there is any gaskets blown because the oil and the coolant are clear.the temp gage has 160 on the top and 260 on the bottom.today,while sitting in a traffic back up for 20 minutes it climbed to about 256 or 257.---thanks ---jp
inspect your system before replacing un-needed parts...radiator and condensor would be my first place to start
