Jaime Posted May 20, 2011 Share Posted May 20, 2011 Hello Can anybody show me how to make my electric fan come on while I'm driving if the tempeture in the engine bay gets over a certain temp and have it run for about 3-5 min after the engine is turned off. I belive that my truck suffers frome heat soak. I have changed everything or cleaned everything from the fuel pump to the ECU. I also plan on installing some vents in the hood but want to try the fan first. I have an 88 long bed 4.0 5 speed with no AC. Thanks in advance. Link to comment Share on other sites More sharing options...
jimoshel Posted May 20, 2011 Share Posted May 20, 2011 Only thing I can think of would be to wire a thermistor into the electric fan circuit, maybe in parallel with one of the heat sensors in the radiator or head and tied into the fan relay Link to comment Share on other sites More sharing options...
Geonovast Posted May 20, 2011 Share Posted May 20, 2011 Replace the fan sensor in the radiator. Link to comment Share on other sites More sharing options...
Jaime Posted May 20, 2011 Author Share Posted May 20, 2011 Will the thermistor run the fan for a few minutes after the enginge is turned off. Replace the fan sensor with what? Or do you mean replace it with another OE sensor. Thanks Link to comment Share on other sites More sharing options...
Geonovast Posted May 20, 2011 Share Posted May 20, 2011 Another OE sensor. Although, really, if it's overheating when you're not pushing the engine and the AC isn't on, you have other issues and a fan running all the time would just be a bandaid. Link to comment Share on other sites More sharing options...
zagscrawler Posted May 20, 2011 Share Posted May 20, 2011 :agree: this sounds like a bandaid to me. What makes you think you suffer from heat soak? fyi everysingle car or truck built suffers from heat soak. The system can compansate for it normally. Is it a starting issue? are you loosing fluid after you shut it off? Also do you have a reliable temp gauge in that bad boy? There is a way to do what you ask but its hard on the battery and not recomended in most cases. Oh and the temp in the engine bay is not as important as the temp in the head and or the rest of the motor. Need a little more info to help ya out :???: Link to comment Share on other sites More sharing options...
Jaime Posted May 20, 2011 Author Share Posted May 20, 2011 This problem started last year. When the tempeture outside is above 70 degrees that is when my problem starts. I start off in the morning traveling about 7 miles, street driving, 15 min or so. I stop for about 45 min then when I get back in, it starts to jerk almost like it's out of fuel at about 25 miles an hour. I get into third gear and the problem goes away. Then it started getting worse sometimes at higher speeds depending on the temp. Oh and it has no gages only idiot lights. Since it started I have replaced the fuel pump and filter, fuel pump regulator, replaced the o rings on the injectors, manifold gasket, plugs, cap, rotor, wires, coil, tps, cps twice. A mechanic has put on his tester cleaned the egr system and the IAC I think it's called. He has told me that it does hold codes after its turned off so he has driven it with the tester hooked up, it acts up but still won't throw a code. He has replaced the distributor and the ECU thinking that might be the problem no luck. He did not charge me saying when he fixes it he will charge me for the diagnosis and the bad part only. But again no luck. He also cleaned the throttle body. When it runs it runs better than it ever has. It should with all the new parts in it I am about ready to take it out in the desert and set it on fire. Link to comment Share on other sites More sharing options...
Jaime Posted May 20, 2011 Author Share Posted May 20, 2011 I sorry mechanic told me that it does not hold the codes when the engine is turn off. My fingers work faster than my brain. Link to comment Share on other sites More sharing options...
zagscrawler Posted May 20, 2011 Share Posted May 20, 2011 Well to be honest it seems by default (shotgun) you might of hit the problem, but sounds like nothing changed? If your mech has is hooked up to a scanner when this happens there should be something going on on his screen. The stumble alone should cause other sensors to respond differently then normal. I'm sure your at wits end but hang in there, i personally would hate to trash a cool ride because of a loose wire or something stupid. To be honest the only thing i can think of suggesting is check things like balast resistor and things in the wiring that may change with temp or get warm as you drive. If i was in your shoes i might acctually take into considerasion that some of the parts you replaced might not be the best also... :dunno: . Also i would be driving it like i was in constant diagnosis all the time, like when it acts up let of the gas in different ranges to see if it changes or go full throttle when it happens to see if it cleans up or kill the engine while it is happening and restart it while still rolling to see if the reset helps, that kinda stuff. Do your best to isolate the problem then tell your mechanic everything you did to help or hurt the prob. Good luck man and don't be afraid to experament, its your truck right lol :wrench: oh and try and ge a temp reading off the head via remote temp gun or some sort of temp devise when this is happening. Link to comment Share on other sites More sharing options...
NewfieMJ Posted May 20, 2011 Share Posted May 20, 2011 I would think after everything that's been replaced , it's the coolant sensor , the one that sends signal to the PCM . I assume there is 2 on the 88 4.0 , the other being for the dash light signal . The only other sensor I have known , not seemingly related to , but still had some weird effects was the 02 sensors . It's pretty common on the 96+OBDII 4.0's but one hell of a hard thing to figure out going in blind . No codes , no CEL's from either mentioned here . Wish I was more familiar with the older systems to further help , I love a challange , lol . Link to comment Share on other sites More sharing options...
Geonovast Posted May 20, 2011 Share Posted May 20, 2011 An 88 will actually have three if it has an original aux fan. One in the back of the head for the light/gauge. One on the bottom/middle-ish driver's side of the block for the ECU. One in the radiator for the fan. Link to comment Share on other sites More sharing options...
Jaime Posted May 20, 2011 Author Share Posted May 20, 2011 I forgot to put it down but I did replace the O2 sensor. I also replaced the catiletic converter not because of this problem just because the old one was trash. Needed to pass smog. The fan is original I think. I looked and found the three sensors. I'll give that a try. When I replace the one at the bottom I'll do a coolant change since it will all come out anyway. Link to comment Share on other sites More sharing options...
maddzz1 Posted May 21, 2011 Share Posted May 21, 2011 Did you put the elec fan in yourself? I thought the elec fan only came stock if you had AC? My 89 doesnt have AC, so no elec fan. Link to comment Share on other sites More sharing options...
Jaime Posted May 21, 2011 Author Share Posted May 21, 2011 No when I got the truck it was already there. Link to comment Share on other sites More sharing options...
Geonovast Posted May 21, 2011 Share Posted May 21, 2011 It also came with the towing package, and I'm sure you could request it from the dealer if you just wanted one. Link to comment Share on other sites More sharing options...
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