mightyjak Posted May 18, 2009 Share Posted May 18, 2009 I drove my 5-speed '87 PF with 161k miles for four hours from Idaho to NV on a 80ish degree day. Any time the engine was under load (interstate, pulling hill after hill) the temp gauge almost pegged out. While the engine was under less load (downhill and once I arrived in town) the temp gauge dropped to normal. Coolant and oil levels are good and the truck runs great. My first thought was thermostat/water pump, but with the temp drop from highway to town driving I'm starting to suspect the fan clutch. Any thoughts? Thanks, Jeff PS: This thing has always been very slow to warm during the winter. I bought it two years ago from a friend and don't know that thermostat/water pump has ever been replaced. Link to comment Share on other sites More sharing options...
87pathy Posted May 18, 2009 Share Posted May 18, 2009 could be a plugged radiator. exactly what mine did. can you keep it cool by turning on the heat full blast? if so, its your rad. Link to comment Share on other sites More sharing options...
Kingman Posted May 18, 2009 Share Posted May 18, 2009 Sounds like your radiator is clogged. That's what my Explorer did, any type of load and the temperature would sky rocket. Link to comment Share on other sites More sharing options...
nunya Posted May 19, 2009 Share Posted May 19, 2009 Just went through the same basic thing, clogged rad, also missing some cores. Switched rad, running temp is perfect now. Link to comment Share on other sites More sharing options...
mightyjak Posted May 19, 2009 Author Share Posted May 19, 2009 Looks like the radiator has been replaced in the past. Did pop the cap off after it cooled down and added a quart or so of H20. Did you guys with similar problems pull and replace or flush and fill at some radiator shop? Link to comment Share on other sites More sharing options...
nunya Posted May 19, 2009 Share Posted May 19, 2009 It's a simple one to yank, plus I personally had and extra one or so laying around. Link to comment Share on other sites More sharing options...
RedPath88 Posted May 19, 2009 Share Posted May 19, 2009 I am also leaning towards a clog somewhere, be it in the radiator or otherwise. But checking the fan clutch should be pretty simple, dos it increase its rotational speed (spin faster) after the engine reaches normal operating temp? This is something you should also be able to hear, once the clutch locks the fan will move more air, which will also produce more sound.. if not, then it's not working properly and is "at least" one of your problems, but maybe not all. Link to comment Share on other sites More sharing options...
Tungsten Posted May 19, 2009 Share Posted May 19, 2009 I am also leaning towards a clog somewhere, be it in the radiator or otherwise. But checking the fan clutch should be pretty simple, dos it increase its rotational speed (spin faster) after the engine reaches normal operating temp? This is something you should also be able to hear, once the clutch locks the fan will move more air, which will also produce more sound.. if not, then it's not working properly and is "at least" one of your problems, but maybe not all. lol i recently replaced a fan clutch that stayed on all the time no matter what i replaced it with a beck and arnley one and now it only goes on after a cold start then goes quiet after a minute or so i'm thinking could the problem be a clog or the automatic trans screwing with the temp since it runs its hot oil through the rad Link to comment Share on other sites More sharing options...
RedPath88 Posted May 19, 2009 Share Posted May 19, 2009 When the clutch fan goes out, it's a good time to consider converting to electric Link to comment Share on other sites More sharing options...
mightyjak Posted May 19, 2009 Author Share Posted May 19, 2009 Thanks for the insight, guys. Tungsten, it's a manual tranny; change your mind any on your prognosis? Guess the deal is this: I'm 230 miles from my tools and workshop. While I can pull the radiator in a hotel parking lot, would there be chance of clearing the clog doing a flush & fill at some shop? I can get the radiator for $120 which isn't bad, but with time constraints and lack of tools a quick flush would be great. The old/new looking radiator appears to be good from the exterior but there's some corrosion in the interior. Link to comment Share on other sites More sharing options...
RedPath88 Posted May 19, 2009 Share Posted May 19, 2009 It "could" work. I'd hate to see you waste your money on a new radiator without knowing for sure if that is the problem, but if you were to replace it, you only need a couple tools to do it... and the cheap generic (below store brand) tools would do it. iirc all you would need is a screw driver or pliers for the hose clamps and a 10 or 12mm socket w/ratchet (or maybe wrenches) to remove the the radiator itself. Also a bucket or other suitable container to catch the coolant. Link to comment Share on other sites More sharing options...
Tungsten Posted May 19, 2009 Share Posted May 19, 2009 Thanks for the insight, guys. Tungsten, it's a manual tranny; change your mind any on your prognosis? oups missed that one yes it definitely needs a good flush then Link to comment Share on other sites More sharing options...
Terrano1992 Posted May 19, 2009 Share Posted May 19, 2009 This thing has always been very slow to warm during the winter. ...and overheats under load, when weather is hot. Bad thermostat (stuck at half-open position)? Link to comment Share on other sites More sharing options...
Precise1 Posted May 19, 2009 Share Posted May 19, 2009 It's definitely not the fan clutch, that would show the opposite symptoms. Cooling ok at speed and temp climbing when going slow/stopped. The fan does nothing for the cooling system over 30-40mph, the wind does it... A quart low is a bit, that could be part of it and did you 'burp' the cooling system to get all the air out? Air can also confuse your sensor. If your gauge was pegged, why didn't it boil over? Sounds like you have some combo of built up scale/corrosion in the passages/radiator (flush should help), funky thermostat and/or radiator issues. I'd have it flushed and then I think you might be able to limp it home (try running the heater full blast with the windows down, no A/C driving at night, etc)) and work on it there if it still isn't good enough. B Link to comment Share on other sites More sharing options...
mightyjak Posted May 20, 2009 Author Share Posted May 20, 2009 I hate to sound ignorant, but where is the burp button and what is the burping procedure? I'm scheduled to drop it off tonight for a flush and fill. Thought I may try burping prior. Link to comment Share on other sites More sharing options...
kh1991 Posted May 20, 2009 Share Posted May 20, 2009 I hate to sound ignorant, but where is the burp button and what is the burping procedure? I'm scheduled to drop it off tonight for a flush and fill. Thought I may try burping prior. how i do it is make sure the radiator cap is the highest point in the cooling system..(park it on an incline or jack the front up a little) then open it and start the car and run it till it gets to normal op temp to when the thermostat opens and allows coolant to start flowing throughout the block.. you'll start to see it bubbling and stuff.. pretty much when it stops bubbling is when the air is out..then turn off and cap.. don't forget to fill the overfill tank.. Link to comment Share on other sites More sharing options...
mightyjak Posted May 20, 2009 Author Share Posted May 20, 2009 Thanks for the advice, kh1991. I tried the debubbling routine and took it for a test spin at 80 on the interstate. The needle was a little below halfway but it's also about 20-25 degrees cooler than when I drove it last. I think I'll go for the flush and fill tomorrow to be safe.... Link to comment Share on other sites More sharing options...
mightyjak Posted May 20, 2009 Author Share Posted May 20, 2009 BTW, sorry to have asked about the 'burp button'. Thought I had read somewhere about a valve built in for bleeding excess air. Link to comment Share on other sites More sharing options...
mightyjak Posted May 21, 2009 Author Share Posted May 21, 2009 Got it flushed and filled yesterday and then flogged it through the mountains. Again, temps were a little cooler, but everything seems to be fine for now. Thanks again for all the advice. Link to comment Share on other sites More sharing options...
Precise1 Posted May 21, 2009 Share Posted May 21, 2009 Cool!! Glad it was so easy and you weren't stuck anywhere, paying for a lot of work... B Link to comment Share on other sites More sharing options...
mightyjak Posted June 7, 2009 Author Share Posted June 7, 2009 It's back again! I haven't driven the truck more than a few miles since I last posted after I had it flushed. I went out today for a drive and it pegged out. Temps are in the high 60s and I was heading up a fairly steep mountain pass when I noticed the temp gauge was pretty much pegged. Turned around immediately and coasted downhill. The temp gauge never dropped significantly. Prior to driving, I had checked all fluid levels, which were good. I noticed the catch can was over the MAX level. To date: I had the radiator flushed a filled and the old man at the shop ran it for 30 minutes on an incline, so I would consider it burped. I've not driven it more than 30 miles in the last two weeks. I figure I'll start with the sending unit since it is easily accessible and cheap. After that, radiator, thermostat and water pump, since if one is pulled the others are accessible. Any suggestions are helpful at this point.... Thanks, Jeff Link to comment Share on other sites More sharing options...
frecklecolouredbrain Posted June 12, 2009 Share Posted June 12, 2009 if you have a manual, turn your radio off and listen to your fan. When it's running, it make A LOT of noise. after about 3000 rpm it stops and your engine sounds really quiet because the clutch kicks in and the fan stops. So, if your running lower rmps it'll stay cool no matter what gear you're in. My advise is to let it warm up while you watch the temp gauge and listen for the engine to drop down in rpm. and mark that spot. if it's not centred then you're gauge is fkt. mine comes out of "open loop" 3/4 up the gauge and sits 1/4" off of 0 degrees when my engine is cold... you might have the same issue. Link to comment Share on other sites More sharing options...
Precise1 Posted June 13, 2009 Share Posted June 13, 2009 Sounds like you are going to do basically what I would. Since it is intermittent, perhaps it is a sticking thermostat, just not all the time?? Can you see scale in the radiator? Definitely change the temp sending unit; until you are sure you are getting a good reading, you could be chasing ghosts... B Link to comment Share on other sites More sharing options...
mightyjak Posted June 15, 2009 Author Share Posted June 15, 2009 Definite scale in the replacement radiator. I keep finding the radiator low by a quart and I can see some antifreeze around the top. I'm going to pull it and get it tested, as well as replace the upper and lower radiator hoses. After that, on to water pump and thermostat.... Sounds like you are going to do basically what I would. Since it is intermittent, perhaps it is a sticking thermostat, just not all the time?? Can you see scale in the radiator?Definitely change the temp sending unit; until you are sure you are getting a good reading, you could be chasing ghosts... B Link to comment Share on other sites More sharing options...
nismothunder Posted June 15, 2009 Share Posted June 15, 2009 For the guy that said he heared about a valve someplace,yes there is a valve on the driver side rear of the engine that you open to bleed off excess air in the cooling system. Link to comment Share on other sites More sharing options...
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