freezerburn Posted September 7, 2007 Share Posted September 7, 2007 (edited) SO I have been having an overheating problem since a few days after I started drivin my new pathy. **** just went for a drive and I realized something, often times an overheat session will occur after just a short spurt of heavy throttle application **** When I changed my oil about a week ago (this was probably 1 week after the problem started I did not notice anything unusual about the dirty oil I drained There was also gunk of a pudding like consistency in the overflow tank which i did a half ass job of cleaning out with my garden hose. I flushed the cooling system repeatedly as soon as my problem began. a compression test revealed: 5 110 6 105 3 102 4 100 1 100 2 80 I think that hammering the throttle down would be causing higher pressures thus forcing exhaust gases into the cooling system causing some temporary vapor lock conditions which is resulting in my overheating problem which mysteriously goes away shortly after it starts. *(average 1-2 minutes duration sometimes more)* Sometimes I can gun it without causing an overheat though but it pretty much does this every time I drive it. anybody have any insight on this? I for one am just about sure its the head gasket. I'm going to empty out my cooling system again tomorrow and see what the liquid looks like and maybe that can further help any diagnosis. I'd love to hear your opinions guys. Edited September 7, 2007 by freezerburn Link to comment Share on other sites More sharing options...
unccpathfinder Posted September 7, 2007 Share Posted September 7, 2007 I dont think you can temp vapor lock these engines...i believe once its locked its locked until it cools down and the air can escape...could possibly be a t stat going bad or weak water pump or slipping belt under heavy acceleration how many miles are on the truck? and was the battery getting weak as you got towards cylinder 6? this will cause a drop in the final read pressures...that being said the "minimum" pressure is 128psi and/or a differential max pres of 14psi...I'd think if the engine has over 150-200k then that could be ok... I would also venture to say that the gage may not be accurate IE 105 PSI may really be something like 130...do you have a way to verify that it is giving accurate readings you can also add a lil oil into cylinder 6 and if the pressure increases this means the rings are worn in that cylinder also if you had a head gasket leak you would have milky oil and oil in the coolant and that doesnt seem to be the case since you described the oil as dirty and not milky I'd retest #6 but with the #'s u have it seems like the head gaskets are good...maybe buildup on the valves that dont let them seat well and the pressures are low but I still think there may be an accuracy issue with the tester... One final thing. when my waterpump was going out it would overheat on city driving and cause leakage from the weep hole but on the highway it got enough air through the radiator and kept it cool enough to keep the pressure from building up as bad and I didn't overheat or leak fluids until it was parked...I did have it vapor lock on me 3 times over the couple months I put off changing it... Link to comment Share on other sites More sharing options...
freezerburn Posted September 7, 2007 Author Share Posted September 7, 2007 (edited) Yeah it was kind of hard to screw on the tester 100% tight due to it having a rubber hose going to the fitting and having to tighten it with that hose alone. (toughest spark plugs i've ever removed) Initially we got 60 on the problem cylinder but I knew I hadn't screwed it on very well (the threads were a little bit crummy on that one I suppose but I finally really gave'r and got it down as much as the other cylinders. On the second attempt we got 80. We cranked the engine over until the reading peaked on the tester and that was it. (about 3-4 times) My belts are 100% My dad was saying that it might be the t-stat too so I'll remove it this weekend and see what happens. Next stop water pump. Thanks for the great reply man. Edited September 7, 2007 by freezerburn Link to comment Share on other sites More sharing options...
unccpathfinder Posted September 7, 2007 Share Posted September 7, 2007 no problem...the only thing with the t stat is I would think it would do it all the time unless its stuck partially open instead of full close or full open...you may want to try to retest and possibly put some teflon tape on the tester to make sure it doesnt leak... I completely understand what your saying about the rubber hose on the tester and trying to install it...its a PITA and when I borrowed my buddies it was very aggravating and then my battery got weak and we couldnt test 4 and 6... you did have all the plugs out right? if not I think this may cause the reading to be a touch lower but could be wrong but i think that (its in the test procedure in the FSM) but i believe if all the plugs are in it can increase the resistance on the crank and possibly reduce the compression in the cylinder? just a thought i dont really know how much that matters tho Link to comment Share on other sites More sharing options...
freezerburn Posted September 7, 2007 Author Share Posted September 7, 2007 yup had all the plugs out when i tested her. I'm pretty confident I was consistent with all the plugs but maybe i'll give it a retest this weekend. It likes to put a little bit of black smoke out when you rev it in neutral if that helps any. I know thats a sign of a rich mixture but I don't think that has anything to do with overheating. The thing runs like a champ aside from the overheating and a mild hesitation that I think might just be the way this engine is. I'm going to clean out the throttle body to see if that has anything to do with it but I doubt it. Holy crap i'm still awake and I have to be up in 5 hours..... Damnit, this pathfinder totally destroy s my sleep schedule I just want to make it perfect. *what do you think about the water pump going* Sometimes it can sit there and idle for any length of time without that needle shooting up. It just shoots up and the strangest times. im going to bed Link to comment Share on other sites More sharing options...
unccpathfinder Posted September 7, 2007 Share Posted September 7, 2007 (edited) yea black smoke is rich...my 87 had that and I never messed with it...I'm not sure what causes intermittent spikes exactly though...I'm sure someone else will chime in...also use the search feature and see what you come up with...I came up with this... http://npora.ipbhost.com//index.php?act=Se...=%2Boverheating BTW welcome to the boards Edited September 7, 2007 by unccpathfinder Link to comment Share on other sites More sharing options...
freezerburn Posted September 8, 2007 Author Share Posted September 8, 2007 EHH FIXED IT!!!!!!!!! It was simply the thermostat. When I took it off I found a sick buildup of some kind of gunky brownish slurry right in front of the t-stat in the housing. I removed the thermostat and reinstalled everything minus the t-stat and fan shroud and the thing won't go over 1/4 temperature on the guage. I flushed the rad while I had it out and found a similar brownish residue when I hosed it. I also cleaned out my surge tank which had the same brown pudding residue in it. Right now I'm going to run it for the next week or so minus thermostat with a bit of laundry detergent flowing through there with just plain old water and get it right clean then i'll buy the 30.00 thermostat and redo everything. That sucker is an absolute bastard to get out holy crap. Had to remove the shroud, fan, and radiator just to get enough room for a socket wrench. Not to mention I had to use a u-joint extension for that bolt thats closest to the block.... I really don't want to have to do that again. Getting that housing back on was the absolute worst part of everything though. Looks like i'll be doin it again next week when i get the new thermostat anyway though... Thanks for the help guys, now she runs like a swiss.... i mean japanese watch hehe. Link to comment Share on other sites More sharing options...
unccpathfinder Posted September 9, 2007 Share Posted September 9, 2007 I donno that I would run it long without a tstat...never heard of putting detergent in there...sorry it was a PITA...I dont remember it being that bad but its been a while...glad thats all it was tho Link to comment Share on other sites More sharing options...
freezerburn Posted September 9, 2007 Author Share Posted September 9, 2007 Yeah it really wasn't that bad only took me a couple of hours to do. Now i've got to figure something out about my four wheel drive actin funny..... Link to comment Share on other sites More sharing options...
freezerburn Posted September 15, 2007 Author Share Posted September 15, 2007 UPDATE: After 1.5 weeks of running without a t-stat and no overheating whatsoever I decided it was time to buy a new T-stat. So, I purchased the new thermostat and thoroughly flushed my engine and rad and cleaned out the overflow tank. Everything was surgical clean. I replaced the thermostat and drove it around and lo and behold the truck overheats EXACTLY like it did before I took it out the first time. THIS is with a brand new 170 thermostat. I bought the 170 just in case i tow some heavy loads on my trailer. SO, the problem is not the thermostat but something else. **When I drained the soapy water mixture after 1.5 weeks of driving without a t-stat it was kinda brownish, same colour as the gunk i took out of my overflow tank but there was no visible oil in the mixture** **After driving around a bit the pipe leading to the thermostat was cool to the touch and so was the lower rad hose** Water pump maybe? Link to comment Share on other sites More sharing options...
blamtro Posted September 15, 2007 Share Posted September 15, 2007 Did you try purging the air out of the system? There is a bolt on top of the engine that will let air pockets out of the coolant system. UPDATE: After 1.5 weeks of running without a t-stat and no overheating whatsoever I decided it was time to buy a new T-stat. So, I purchased the new thermostat and thoroughly flushed my engine and rad and cleaned out the overflow tank. Everything was surgical clean. I replaced the thermostat and drove it around and lo and behold the truck overheats EXACTLY like it did before I took it out the first time. THIS is with a brand new 170 thermostat. I bought the 170 just in case i tow some heavy loads on my trailer. SO, the problem is not the thermostat but something else. **When I drained the soapy water mixture after 1.5 weeks of driving without a t-stat it was kinda brownish, same colour as the gunk i took out of my overflow tank but there was no visible oil in the mixture** **After driving around a bit the pipe leading to the thermostat was cool to the touch and so was the lower rad hose** Water pump maybe? Link to comment Share on other sites More sharing options...
freezerburn Posted September 15, 2007 Author Share Posted September 15, 2007 Hahahaa, I'm such a pessimist! It runs solidly below centerline on the temp guage. I just took it for a bit of a highway drive and all the air has gotten itself out. Everything is peachy now. Link to comment Share on other sites More sharing options...
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