tisker Posted September 4, 2014 Share Posted September 4, 2014 I have an 87 4.0 that is having over heating issues. the aux fan isnt coming on, with ac or not. I have replaced the relay and socket, checked the the electric cooling fan connector. on top of that my coolant is boiling at just under 210. seals and everything are solid, just had it compression tested and some minor things fixed. thinking of wiring a bypass for the electric fan, but would prefer to stay away from that route. anything else i should check before I make the jump and bypass it?I'm not too mechanically inclined, and this truck has been teaching me allot. any help would be greatly appreciated. Link to comment Share on other sites More sharing options...
johnj92131 Posted September 4, 2014 Share Posted September 4, 2014 How do you know the radiator is boiling at 210? Not being a smart @$$. How do you know the fan doesn't come on when the switch reaches 210/215/? i am wondering if your water pump and the thermostat are good. I would check that sensor in boiling water to see if it turns on or not. Then I would see if your fan runs when you bypass the sensor.. Lots of things to check. Link to comment Share on other sites More sharing options...
tisker Posted September 4, 2014 Author Share Posted September 4, 2014 its reading 210 on my cluster and boiling out the pressure tank. about to swap the lid to make sure its holding pressure to keep it from boiling (though the lid still feels like it fits snug.) . at 210 it starts to build so much pressure it started leaking out the pressure tank. I tested the fan via dc battery. just changed the water pump(and can feel flow through the hoses when on and running)i have to check to see if the tstat is good. and am about to do a flush since the truck sat for four years and ive been trying to bring her back to life. Link to comment Share on other sites More sharing options...
nitroxsteve Posted September 4, 2014 Share Posted September 4, 2014 Water boils at 212F if it's not under pressure, sounds like you need to fix your pressure leaks first then see what happens. Link to comment Share on other sites More sharing options...
thejim42 Posted September 4, 2014 Share Posted September 4, 2014 Get a laser thermometer and make sure your gauge is accurate aswell Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 Ok so new lid fixed the boiling issue. It's still running warmer than it was but it's sitting at 210 which from what I've read is not bad. Tho the aux fan still is not kicking on, even when it spiked to 225~ and still does not kick on with the ac. Link to comment Share on other sites More sharing options...
johnj92131 Posted September 5, 2014 Share Posted September 5, 2014 If the engine has sat for 4 years, replace the thermostat right now. The old one is junk, just replace it and be done with it. And no way you can trust any engine temperature gauge on any car to be accurate. Ever. Sounds like you are making progress. Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 5, 2014 Share Posted September 5, 2014 Have to ask: have you hot-wired the fan directly to the battery to test if the fan even runs? Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 It sat for four years and we got it running last year. I just acquired it and have been fixing the stuff they neglected. They just got it running and abused it. They did change the tstat last year, as I just called them and asked. Losing daylight, so ima check that and switches tomorrow. There are three(?) switches that could be problematic? Which would be most likely culprit? Hornbrod yes i did. Fan is strong. Thanks so much everyone for the help thus far. Link to comment Share on other sites More sharing options...
nitroxsteve Posted September 5, 2014 Share Posted September 5, 2014 When is it hitting 210? Driving ? sitting in the driveway idling? Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 its started to over heat while stuck in traffic the other day, and started to boil the coolant. since then ive been testing via driveway idle. when i drive, it drops to 170-190 range. now the main focus is the AUX fan. being in the desert i need it for my ac and for when i get stuck in traffic and the desert starts baking my engine. daylights about to be coming, so ima get back at it today. Link to comment Share on other sites More sharing options...
yxmj Posted September 5, 2014 Share Posted September 5, 2014 Just putting it out there.....you can make an easy circuit with an interior cab switch and an under hood relay to add manual control of the fan.....so you can turn it on when you feel you need it. . :MJ 1: . Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 been heavily weighing that option, being that most people end up going this route when the aux fan starts acting up. id like to exhaust all my options before i start to drill the fire wall and add a switch tho. Link to comment Share on other sites More sharing options...
johnj92131 Posted September 5, 2014 Share Posted September 5, 2014 Located in the desert??? Nice to know. Just where are you located? Death Valley? High Desert in So. Calif? Arizona? Nevada? Did you test the Aux Fan directly to the battery? or just the main fan. The Police package in a Cherokee had a switch to force the aux fan on, so it is not quite the kludge solution you might first think. There is a factory version solution. BUT still best to get the aux fan running properly. Replace what you have to. Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 I'm in vegas atm. House hunting in co. So looking to make the jump soon. And yes, i tested the aux fan via battery, was running strong. Didnt know about the police package Cherokee. Good little bit if info. Gonna start plotting a possible bypass switch today if I can't get it to kick in. Link to comment Share on other sites More sharing options...
nitroxsteve Posted September 5, 2014 Share Posted September 5, 2014 I know your electric fan is not functioning but also check the mechanical fan clutch they don't last too long and will cause it to heat up when stopped. Link to comment Share on other sites More sharing options...
nitroxsteve Posted September 5, 2014 Share Posted September 5, 2014 I know your electric fan is not functioning but also check the mechanical fan clutch they don't last too long and will cause it to heat up when stopped. Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 just did the cold spin test on the mechanical clutch fan. got a 1/8-1/4 rotation cold. and about 1/2 rotation warm. i read that they shouldnt have play (IE be able to rotate back and forth)(it doesnt have play like a bad motor for say an ac unit) is this true? it appears to grab around 225 and kick in higher to drop the temp down to 200-210, according to my cluster. that being said it sounds like its doing all it needs to do. is there any other way to test it? Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 officially found the problem. a pinhole in my radiator, i drove it long enough that it started to get past the 225 range on my cluster. parked it popped the hood, the pressure caused the pinhole to spread, and a visible leak became apparent Link to comment Share on other sites More sharing options...
nitroxsteve Posted September 5, 2014 Share Posted September 5, 2014 Mechanical fan should turn less when hot (more resistance to spinning) not more , it sounds like cluth is bad. My electric fan doesn't kink in till well above 210 but it does kick on with a/c. Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 so I'm gonna upgrade the cooling system since my radiator is bad. is it advised that i just move to an electric fan for my main fan, or should i just replace the clutch? ::edit::after much more searching I'm opting for a swap. thanks for all the help everyone. really appreciate everything. Link to comment Share on other sites More sharing options...
hillbilly51 Posted September 5, 2014 Share Posted September 5, 2014 " just changed the water pump(and can feel flow through the hoses when on and running)" I don't know if the 87 model 4.0 is the same as my 88 model 4.0 but when you changed the water pump did you.......? 1.....Make sure that you got the correct water pump. They make a cw rotation and a ccw rotation impeller. If you put the wrong one on, that would cause a big cooling problem. Did you compare the old one to the new one? 2....Are you sure that you got the serpentine belt on correctly?....assuming that the 87 model is the same as the 88. On the 88 model it is possible to install the belt so that the water pump will spin in reverse direction. That would cause a big cooling problem Just a couple of ideas Hope this helps steve Link to comment Share on other sites More sharing options...
johnj92131 Posted September 5, 2014 Share Posted September 5, 2014 Several good radiator threads here in the last couple of months. http://comancheclub.com/topic/43874-radiator-source/?hl=radiator http://comancheclub.com/topic/43895-another-coolant-thread-boiling/?hl=radiator http://comancheclub.com/topic/44029-radiator-leaking/?hl=radiator http://comancheclub.com/topic/44110-what-radiator/?hl=radiator Even the factory heavy duty radiator is just a slingle row radiator, so save some money and don't buy an expensive one. Unfortunately, they are mostly CRAP (Chinese Auto Replacement Parts). Link to comment Share on other sites More sharing options...
tisker Posted September 5, 2014 Author Share Posted September 5, 2014 yes to all those steve.been already bouncing around the forums looking at radiator upgrades. thinking ima go ffd (emailed them and asked if i can get one without the fans and shrouds.waiting to hear back) like hornbrod's. three years and still going strong, plus all aluminum. i wanna do all i can for this cooling system since I'm in vegas, and even when i move ill be at high elevation in CO. Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 5, 2014 Share Posted September 5, 2014 If you do get the FFD rad, consider converting to the open cooling system. Less troublesome and easier to burp than what you have. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now