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79FJ40 overheating

Discussion in '40- & 55-Series Tech' started by crewzerdog, Jan 17, 2004.

  1. crewzerdog

    crewzerdog

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    Trying to finish up a complete frame-off restoration of a 1979Fj40 - its basically all back together and "drive-able" except for 1) an overheating problem and 2) a carb adjustment issue. Some background - the 2F engine was rebuilt with new crank, rings, bearings, etc. - have good oil pressure.

    Now about the overheating issue -- all new hoses/clamps, belts, and thermostat. Prior to rebuild the engine ran "cool". I've since replaced the radiator and radiator cap - still no luck -- truck warms up within about 4-5 minutes to normal range but then temp continues to gradually but steadily elevate to very close to the "H" range. Radiator does not "boil-over". No leaks from the water pump or anywhere else. Radiator hoses on top and bottom are quite hot to the touch.

    Short of replacing the water pump - any suggestions to trouble shooting this? I thought about replacing the temp sending unit that screws in to the manifold just to be sure it is functioning correctly. Only other things that come to mind are the fan clutch (it was working prior to rebuild so don't think this is the problem) and the temp guage in the cluster itself. With no leaks or screeching from the water pump - any way to easliy check its performance? Suggestions welcomed.

    #2 - carb issues - finally got the distributor back in and the timing set darn close. The factory carb was completely rebuilt. Engine cranks easily and runs fine as long as the choke is 3/4 out -- if not then gas pedal has to be pushed down to keep engine RPMs up or it will stall. Even when the engine heats up (see above) still must have choke pulled out to "idle". Sounds like a fuel problem to me but I've adjusted the fuel mix and idle screws per factory manual...I've also plugged all the carb vacuum ports to avoid any suspected air "leaks". What next?

    Thanks for any help sent this way, Tom
     
  2. fsusteve

    fsusteve

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    Are you running a shroud on the radiator?
     
  3. crewzerdog

    crewzerdog

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    yep, its the factory/OEM shroud as is everything else - I've tried to stay "original" on this restoration.
     
  4. fsusteve

    fsusteve

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    If it's heating up just around town, I would suspect the fan clutch. To check the water pump, take the cap off and start it up and when it gets to temp, the thermostat will open and you should see water/coolant flowing.
     
  5. Landpimp

    Landpimp

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    as stated above it could be the fan clutch, but I suspect it's not. You can test the fan clutch, warm up engine, raise RPM's to 1k, close hood, block off grill(cardboard or whatever) pretty soon you will hear the fan kick in, will sound like a jet taking off, remove cover over rad and it should quite down or spray water on the rad and it will do the same.

    waterpumps normaly leak or make noise when bad or going bad.

    this fall I had the carb rebuilt on my fj60, before it didn't overheat, after the rebuild it did. What happened? well the rebuilt carb(as well as motor in your case) was making more power(then before with old carb/motor).....and more power= more heat. The cure was a new rad(I used a Performance Radiator) You could also have your rodded out or recored, I went new. Also can run a 180deg t-stat(OEM in 75 2f)

    A SUPER handy tool it a Raytech non contact thermo($80), just point it at whatever and it tells you the temp. Also the temps will be 10+deg hotter at the head then the t-stat. If you can hold your hand on the upper hose without great discomfort then its prolly not over heating, if you cant hold your hand for more than a few seconds then it's prolly overheating.

    do the sender and guage match? what i mean is your not using a different motor(and sender) than it had before. I doubt its the guage or sender.


    not sure about the carb, maybe a bad idle selnoid? I have had misserible expence with all but one rebuilt carbs, my fj40 carb needs a rebuild(not horible now but its time) what am I gonna do? spend $600 for a brand new OEM Aisin carb, $600 is a lot but its brand new!

    John H
     
  6. crewzerdog

    crewzerdog

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    John H. - I'm running the same instrument cluster (no mods) and same temp sending unit as before the rebuild. I have access to a non-contact temp gun (infra-red unit I believe) and I'll check that along with the suggestions on the fan clutch. I assume I should be comparing temps on the upper and lower rad hoses but what other measurements would be beneficial to compare?

    While the thermostat is new - not beyond reason for it to be bad - had it happen before with 'new' ones on other vehicles. I should have checked it in a pot of hot water on the stove before installing it. Getting tired of draining that :-X radiator.

    On the carb - you may be right on target with the suggestion of idle solenoid - I have a used spare in the basement and I'll give it a try. Can I just unplug this from the wiring harness or does it have to be hooked up? I don't recall this being hooked up before as previous owner told me that he actually had installed a 78 carb on this truck within a few weeks of buying the truck from the Toyota dealer - he said he wanted to get all the smog $%^# off it including the cat-converter - he lived in Montana on a farm and didn't want to start a grass/hay fire driving the truck in the fields. I also assume none of the vacuum lines coming out of the carb have to be connected and should be blocked off for now. Thanks again, Tom
     
  7. Landpimp

    Landpimp

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    I would shoot the temp at the t-stat housing and head, should be 190ish at t-stat, prolly 200 at head if its cooling correctly. Even the upper hose will show alot lower than the t-stat housing, lower hose should be MUCH cooler than the upper. Also check the rad itself, look for any cold spots.

    Could be a bad t-stat, but I have yet to get a OEM that was bad.

    If just changing t-stat I usally don't bother draining the rad, just pop the hose off, yeah you lose a bit of coolent but not much.

    Like I mentioned, I suspect its just that your new carb and rebuilt motor is now making more power and heat, so while the old rad kept up with the tired carb and motor it can't keep up with the new motor and carb anymore, this was exactly the case on my fj60, never ran hot till the new carb(and carb was not running lean or rich) But a lean(I think) carb can create more heat.....so check that out as well.

    On my carbs(all late model 40/60) the idel selnoid plugs into the harness, unscrews out of the carb, check the little o-ring as well. But honestly......I'm pretty(OK very) clueless when it comes to carbs.

    1st thing I would do is borrow that temp gun.......it will tell you alot.

    John


    [quote author=crewzerdog link=board=1;threadid=10230;start=msg91419#msg91419 date=1074382225]
    John H. - I'm running the same instrument cluster (no mods) and same temp sending unit as before the rebuild. I have access to a non-contact temp gun (infra-red unit I believe) and I'll check that along with the suggestions on the fan clutch. I assume I should be comparing temps on the upper and lower rad hoses but what other measurements would be beneficial to compare?

    While the thermostat is new - not beyond reason for it to be bad - had it happen before with 'new' ones on other vehicles. I should have checked it in a pot of hot water on the stove before installing it. Getting tired of draining that :-X radiator.

    On
    On the carb - you may be right on target with the suggestion of idle solenoid - I have a used spare in the basement and I'll give it a try. Can I just unplug this from the wiring harness or does it have to be hooked up? I don't recall this being hooked up before as previous owner told me that he actually had installed a 78 carb on this truck within a few weeks of buying the truck from the Toyota dealer - he said he wanted to get all the smog $%^# off it including the cat-converter - he lived in Montana on a farm and didn't want to start a grass/hay fire driving the truck in the fields. I also assume none of the vacuum lines coming out of the carb have to be connected and should be blocked off for now. Thanks again, Tom
    [/quote]
     
  8. Archengine

    Archengine

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    Aside from the above, all I can think to add is the possibility of air-gaps in your block and radiator. Pop the drain at the bottom of the block and open the t-stat, pour water in irectly, this will help out alot, also it helps to have the front end of the truck higher than the back when doing so. My truck never gets close to operating temps in 4-5 min, more like 8-10 for me. Feel the rad and main hoses to determine if coolant is actually flowing through rad, and definately get the t-stat checked in a tub of water. Did you put the stat in right, with the proper gaskets? What happens if you leave the stat out? If this and the above comments don't solve your problem, I would suspect something is blocking the path of the water flow. Maybe during the engine rebuild, or if you left your passages exposed while working on the truck, you might have a dead mouse floating in your block, or a nest of some sort.
     
  9. crewzerdog

    crewzerdog

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    Archengine - great suggestions keeping coming. Thanks -the air gaps could be a possibility as well. In all the manuals I have there is nothing mentioned about opening the block drain plug. On any other engines that I've tinkered with over the years, there is generally some 'valve' that can be cracked open at a 'high elevation on the engine' to eliminate those air gaps - but nothing like this on the cruiser. I thought about unscrewing the emission plug on the top of the thermostat housing to accomplish this or maybe unhook the heater hose connection at the top rear of the engine block - I thought to eliminate air "gaps" you needed to do this as high in the system as possible so I guess either of those two places should work.

    The thermostat gaskets are OEM and I "studied" the factory manual to be sure that sucker went in right - not wanting to do it again. Well, that "plan" sure got busted :mad: I think I'm going to pull the thermostat - test it and while it's out reconnect it all and run the engine without the #@$ thing. With the new radiator and essentially "straight piping" the engine should cool down - if not, the fan clutch and/or water pump are the problems. BTW, the block was well protected during the rebuild process - all holes covered. Guess I have to stay optimistic - after 14 months of knuckle busting work - a few more weeks I'll have this thing on the road!.
    After all it's only $$$. Thanks.
     
  10. Archengine

    Archengine

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    If it makes you feel better, I spent 18 months rebuilding my truck, and had a demon in my harness that took 3 weeks to solve, out there every day for 8 hours. I nearly poured gas on the $%#^@ and lit the match. It's really frustrating when everything else is set to go, and your this close to driving it. FYI, theres a block drain on the drivers side of the block, near the firewall, just above the steering box, crack that a little and flush out the built up crud, then just put the hose in the stat opening and let her flow for awhile. It's amazing the buildup that accumulates. This should help out. Keep me posted on this crap, I'm interested what has caused this. Mine did this aswell, but was just air in the block.
     
  11. crewzerdog

    crewzerdog

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    Archengine -- you da' man!! I decided to "bleed" the coolant system before pulling the thermostat back out. The "air gap" in the coolant system must have been the problem - once I was able to "bleed" the block the temp gauge made an immediate drop and stablized mid-range. Nice :D I also found out the new radiator has a pin-hole sized leak. :mad: Think I've got this issue solved. Thanks to all.

    On the carb - I've kept adjusting the OEM carb and just about have the baby idling without the choke. I even took the truck for a quick spin down the driveway and up the street. First "run" in over 14 months!! :beer:
     
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