Ok i have a 91 5.0rs and its has been damned hot here lately (96*f at about 106 heat index out at the airport so its atleast 100 in traffic) and my 91 rs keeps trying to boil over. I have alread replaced the fan motor since it died recently and the coolent has been flused, also the previouse owner had just recently replaced the water pump (and yes its new i have checked). I can hit the ac switch (since the ac is dead right now) and get the fan on, but of course it becomes heat soaked and slowly becomes less and less effective driveing the engine temp up. I do not have an air dam as of right now and i am planning on getting one, but they don't do much in stop and go traffic. In fact the car gets so hot today i stopped and got out to go inside and could hear the overflow tank boiling. My caps are good and hoses are new. I am thinking i may have a worn t-stat that is only opening partially. Is this possible? My temp guage has to be fairly close since i have the stock fan switch and i can watch at the 240 mark it will bob down for a bit. Should i check to see if something else is dragging on the engine (something in the serpantine system?)? Also is there anybody that makes an aftermarket high flow single fan that would fit were the stock fan is without haveing to hack bits out? I really do enjoy the car, but only being able to drive at night is going to become a problem. Oh it gets to the redlines after about 30-40 minutes in traffic.

 

Check to make sure you don't have any debris in front of the radiator. When I changed my radiator out last summer it had about 6" of leaves jammed up in front of it. Between the radiator and the AC condensor. I don't know how the managed to get in there but they were definitely hurting my cooling. I also run a 170* tstat now to give me a little more room. Heat still works fine. Had to go to the dealer to get 170* stat. Would have gone to 160* but I have heard that can cause problems with computer going into closed loop mode.

 

Well i just went out and checked the front of the radiator and theres nothing blocking it except the ac core. The ac cor itself is also clear and damned near perfect. Is it possible that a worn t-stat could be only opening part way?

 

1: Get the air dam. Not only dose it force air up into the radiator at speed, but at idle it helps keep the fan from circulating the hot engine bay air through the radiator.

2: When you put on the new fan motor did you put the spacer between blade and motor? If not the fan blades may be to far away from the radiator. The gap left by the factory was marginal far safe cooling as it was.

3. Your radiator may be clogged internaly and not working properly. Which happens with older cars. Either have it recored or just by a new one.

4. Replace your thermostat with a 180* one imediatley! I costs under $5 and takes 10min. There is no excuse not to. Exspecialy if your having cooling problems

5. Is the fan turning on at the proper time? The electronics that contol this can go bad. You may have to wire in a seperate switsh for it.

Good luck. Hope this helps.

 

I know this sounds crazy, but have you tried to run the heater on "HOT"? Try it and see if you get heat.

The reason I say this is....

A while ago I put in a 180* T-stat, a Hypertech 200* fan switch, and also flushed the coolant. It was doing great, but then when the weather started to change from cold to warm, then to cold again, I noticed that occasionally I wouldn't get heat.

I checked under the hood, and outta frustration, I whapped the heater control valve against the intake manifold a couple of times. It worked and I got heat.

One day when it was 95*+ outside, I was out burning gas, had the AC cranked, and looked down at my temp guage to see that it was WELL into the red!!!! I turned off the AC, switched it to "Heat" and cranked the lever over to "HOT" in attempt to cool the coolant. Well I didn't get any heat from the heater core. So right in the middle of the red light, I popped the hood and did the "Fonz" trick. While I was under there I noticed the overflow tank was about 1" from being COMPLETELY full. I almost peed my pants I was soo scared.

Needless to say, I changed the Heater Control Valve, that day. It was about $40 IIRC, and took a whole 10 minutes. Ever since I did that, the temp guage hasn't gone over 200*, even in 100* weather.

The guy at AutoZone thought I was nuts and said there was no way that the Heater Control Valve would cause the car to overheat. Shows how much he knows.... Damn order takers!!!

So.... to make it a short answer, change the T-stat to a 180* one, change the fan switch to one that goes on a ~200*/off at ~185*, and check that Heater Control Valve.

Good luck,
AJ

 

I did the "fonz trick" on mine, the damn thing broke into three pieces and I got a burned hand for my trouble. Only cost me the small sum of $60 and a 5 day wait to get a new one!

 

Get the air dam!!

As I said in an earlier thread, I went to Home Depot and got some wall edging and extended the air dam length about 2". Has kept the engine about 30 degrees cooler.

Also make sure that you are running the right coolant mixture. I think it is about 2 gallons to make the ratio correct. I checked the chiltons manual and it refers that the car should hold 16qts of coolant, which is 4 gallons total. Divide that by 2 and you get your 2 gallons of anti-freeze.

The thirdgens need the air dam.

Jim.

 

The headaches that comes with cooked motors like blown head gaskets are not worth not having cheap air damns or not replacing a 5 dollar T stat.

 

i know it sounds easy and very simple but check and make sure u ahve aenough water init. Mine boiled over once b/c t-stat was broke i took it out then mar car still overheated. didnt have ebnough coolant. so fill it all the way up then turn the car on with the cap off. (if water shoots out at you ur head gasket is ****ed) if water doesnt shoot out at you then keep filling it until its at the top. My radiator has prob 1/4 to 1/3 the rows clogged and w/o a t-stat and a full coolant system it stays below the first mark on the guage make sure the radiator isnt leaking cause if it dont hold coolant then your gonna have air in the system and air in a water coolant system is no good. i learned the hard way. btw i ahve a 90 305 tbi 5-speed

 

Let's see,......

Air dam....check.

Right amount of coolant......check.

Correct 195 degree Tstat.....check.

Additional length of air dam from Home Depot......check.

Car runs 30 degrees cooler without changing Tstat.....check.

No problems since.......check.



So, with a cooler engine......how can I blow it or the heads?