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Thread: overheat?

  1. #1

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    overheat?

    A few years back I blew the head on an overheat. Apparently it had been running hot for a long time but my gauges only work intermittently so I'm used to ignoring them. Today I went to a shop not a half mile from home. It had a spot of water under it that looked like the overflow hose had released some from the overflow canister. Its not full its just below the full line.
    From there after it sat for two hours I drove maybe 5 miles when I got home it seemed very warm so I lifted the release latch on the rad cap and the overflow tank started to boil. I do not think it should be this hot for that short of a drive especially since was cool out.
    I have a new radiator, a new shroud the fan is always moving whenever I lift the hood with it running, the thermostat is whatever NAPA gave me, I even replaced the heater core with one that had a working valve when I did the head and it worked fine. I also recently replaced the cap that plugs the water choke branch.
    The only suspect thing I have is that when I open the cap and run it until the thermostat opens. Then if I rev it up the level of coolant drops to the top of the fins and if I have a funnel there it will rise up and let loose bubbles in the rising liquid when I let the revs drop. No matter how many times I do this I get bubbles. Am I just not getting all the air out or is air being sucked in somewhere?

  2. #2



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    Put a radiator pressure tester on it. Pump it to about 5 PSI and start the truck. If the head gasket is bad it will rise up quick (the pressure that is). The level of the water going up and down is normal as you rev it.
    To remove all bubbles you must use the overflow and just keep it full.

    The boiling noise you herd might have just been trapped air because the water level was low in the radiator.
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  3. #3

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    I had filled it yesterday after installing the new carb. I spent 25 minutes doing it to be sure I had it filled. The bubbling was in the overflow it was coming from the bypass on teh top of the radiator when I lifted the pressure release latch.
    ll look into getting a pressure tester.

  4. #4

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    I just got a kit from Advanced Auto Parts and nothing in it would fit the cap. It had like 30 caps in it and the only two with the right style were way small. I have an after market radiator in it but its basically the same one only alum and plastic. So what radiator pressure test kit are you guys using? I have the G63B 2.0

  5. #5

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    I ordered a new thermostat for 180 degrees and a molded rubber upper hose to replace the corrugated one I have that may be reducing flow. The lower temp thermostat is to get it to start cooling sooner and slow down the cascade of events. I sent RA an email to ask them to make sure that pressure tester they sell will fit the neck of my radiator. 1.75" inner dia of the filler neck and 2.25 is the outer lip that catches the cap. I am using a Stant pressure relief cap with the lever in the middle 13psi. The picture they show does not show the inside of the cap on that tool so I can't tell if it is threaded which would not work or if it has the two lips to grab the lips at the top of the neck.

  6. #6

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    I found a pressure tester. I hooked it up pumped it to 7 and started it let it run for 5 minutes. The thermostat never opened. The pressure stayed dead steady. I only thought after I drove 20 miles to return it that maybe I should have let it run until the thermostat opened???

  7. #7

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    You needed to run it until you had coolant flow and the engine was up to operating temperature.

  8. #8

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    Thanks geez. I got it again and put it on and watered the garden.Came back and it was up to 12 then went up to 13/14psi then 15. I came in and put a timer on for 10 minutes and will go out to see what it says then. The upper hose was too hot to hold onto when I came in. Oh yea my gauges are working at the moment and the temp indicator is just past 1/2.

  9. #9

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    Went out after the 10 minutes and it was still at 15psi. That is obviously higher than the 13psi limit of the stock cap. I have no idea what it might mean. Maybe I never torqued the head properly? Or maybe it wasn't milled flat when I installed it out of box? or maybe the intake is leaking? AFAIK everything is as tight as possible. I even re torqued the head last fall because I never did it a second time after installing it and I have checked the intake at least twice since the new head because I was trying to eliminate it as a source of the poor MPGs.
    I look forward to your input gentlemen.

  10. #10

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    Have you removed the radiator and back-flushed it?
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  11. #11

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    Quote Originally Posted by royster View Post
    Have you removed the radiator and back-flushed it?
    No. It is pretty new radiator I installed it when I put the rebuilt head on. That was a couple years ago but I haven't driven it very much. The coolant is clean no visible contaminates.

  12. #12

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    There is a guy on a Dakota forum I belong to who has had similar issues. He eventually found the issue was multiple from a corrugated hose to a bad Chinesium thermostat. He ended up doing this Super Flush https://www.youtube.com/watch?v=s--5ft5YiHg Which is what I am going to start today. I'll wait until the parts I ordered arrive to complete it. I'm going to drive it to return the pressure tester just to see how hot it gets. Hopefully the gauges will work today I really do have to make time to look over the wiring diagrams so I can chase that intermittent issue.

  13. #13

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    Well I have a point shoot thermometer and its cooler at the exit hose than the top hose which is 153 is the base is in the 120's the thermostat housing is in the 175-183 range. The block under the exhaust is 253 the water choke tee is 170ish.
    Yet I have no heat from the heater to speak of. The air is definitely warmer when I turn on the heat but not even close to how hot it is outside mid/high 80's. The heater unit I got from the junkyard seemed OK and the valve opened and closed well which is why I changed out the old one. Can it be the core is plugged?
    Anyway I have removed the thermostat which is a 180 and looks fine and let water out when I opened the housing hot. I have added Prestone flush which I will run for a few days then do that super flush once the new hose and thermostat come in. Any ideas on diagnosing the heater? What is the total amount of coolant this thing (2.0) should take?

    EDIT I forgot to put the PCV back on when I removed the thermostat and the idle went way up when I started it and if I revved it to make it go down it would die. Scared me for a sec on that.
    Last edited by 85Ram50; 07-24-2017 at 12:16 PM.

  14. #14



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    OK first thing to do is look at things the mechanical way.
    #1: What is the max temp you have seen. If you do not know then go pick up a real gauge and drop it in so you have a number to go from.
    You only need a cheep one unless you are going to keep it on there forever.

    #2: Did you open the heater valve at fill up? if not it will always have trapped air tell you open it.

    #3: Is the heater getting hot. If not something is plugged. I have seen the metal tube that runs around the right side of the engine get plugged or rust apart and leek. Stick a wire through everything or use light if you can. Heat is good to keep the window clear in winter. AC is a luxury item for the Snow Flakes. All D-50 and MM owners are sweat resistant and know the crank handles on the doors are the main climate controllers. LOL

    #4: When checking the pressure you said it held 15 for 10 minutes after running. That is good. So no head problems there. If there was a problem it would have gone from 0 to 60 in nothing flat. And if it was a @ 15 and dropping after shutting down then it would have been going into the engine.

    #5: The bubbles in the overflow is normal. It will always bubble tell every last drop of air is gone. It could take days for them to go away. OR if there is a hot spot on a cylinder wall it may always make some air. But that is not a problem to think about yet.

    #6: Drop in a good Stant T-stat so you know it will work.

    (TRICKS of the trade)
    Drill a small pin hole in the flat flange of the new T-Stat. 1/16" or less is plenty, it's only air and will not affect how it works or cools. This will allow air to escape during filling. Some may already have the hole with a H bar in it. Coat the gasket lightly with some anti-seze before putting it together. It will make life easy the next time you take it apart 10 years from now. anti-seze is a wonder drug on gaskets, intakes, carbs, and water systems. Saves you time and makes it so you can reuse it if need be when on the road or at a camp spot hours from parts.

    #6: Fan shroud. Does it have one? If not get one for a Montero early version. Any time a fan is more then 1 inch away it should have a shroud.

    #7: Fan clutch. (1) Does it have any Resistance when you turn it? (2) Do you see any gray matter coming out of it? (3) Is the bi metal spring on the front of it missing? If no to #1 or yes to #2-3 replace it.

    #8: last is the water pump. Does it have movement in the shaft or just the fan and clutch. The clutch will have movement. If you have access to a baroscope you can look in and see the impeller. I have seen impellers come loose from the shaft and I have also seen the area behind the impeller get worn and pitted from cavitation and bad water.
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  15. #15

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    1. I only know the temp from the gauge or the point and shoot. Where does one plug in an after market temp gauge? I was looking at some rad caps with temp gauges in them are they any good?
    2 Yes I opened the heater turned the fan up and ran it just like Eric the car guy.
    3 Never considered that pipe getting plugged. I was thinking heater core. I had to use a bit o RTV to make it seal when I redid the timing belt and installed the new pump.
    4. I didn't actually pay attention to how long it held after I shut down. but after 10 minutes of it not cooling down and dropping pressure fast enough for me I hosed the rad down so I could remove the pressure tester and it still spouted a bit when I broke the seal after I got it down to 5psi.
    5. Cool
    6. coming from Rock Auto.
    7. I put n the shroud last year. New metal MB stock part. $$$ I happen to have an extra top half they sent me two??
    8. The fan has slight resistance. It is plastic with metal and I felt the spring on front. It is always spinning when I lift the hood with it running. I have never seen it not spin with the motor running.
    9. Only the fan clutch moves. I've not pulled off the hoses to look at the water punp yet. All signs say it is working the water really started moving fast across the top of the rad once I removed the thermostat to put in the flush.

    Question- If I fill the heater from one of the hoses that come out the firwall will the liquid come out the other hose if the valve is open?

  16. #16

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    I found a thread on here when searching for a temp gauge that explained what to do about failed dash. It seems to have worked, I had a dead fuse. I also did some research on the fan and found this https://itstillruns.com/test-fan-clutch-5086903.html
    I ordered a new clutch just to be sure. I suspect the fan clutch is stuck on. Hopefully that is what's affecting the heater. I also found an old post of mine back when I first fixed the blown head where I thought the cooling system was working too well and I had to use cardboard in front of the rad in winter. I had forgotten that. The fan clutch might also be a source of the poor gas mileage.

  17. #17



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    Yes you can "back flush" the heater. It's just hard to get to the hoses. I'm not convinced it's over heating. For a gauge you can stick in where the stock one is at. Just use a T on the T-stat housing. It's fine to run 200. That is not that hot.
    for every 1 psi of pressure added to the system it will raise the boiling point of water by 3 deg. That's why we use a 13 psi cap. It gives you 39 extra deg.
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  18. #18

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    OK. I will probably do the back flush on the heater and pull that pipe at the same time. Stant specs say the 13 psi cap is 12-16psi range. The dash gauges worked when I drove it last night (never got up to halfway on the temp) but the left blinker stopped flashing inside again?? The right one is working inside. They both work outside. Throttle got stuck on the way home last eve! had me worried. I replaced the cable and sprayed the linkage and throttle cable tube with dry lube. Its another brand like Lock Ease, basically carbon dust in alcohol. Drove it round the block today no probs.
    You can use a cable from a bicycle $3 to replace the throttle cable then cut it to fit.

  19. #19

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    Quote Originally Posted by 85Ram50 View Post
    left blinker stopped flashing inside again
    low blinker fluid? sorry bud but i had too

  20. #20

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    Quote Originally Posted by jamesw View Post
    low blinker fluid? sorry bud but i had too
    Wonder if fender stop-leak would work?? http://www.mightyram50.net/vbulletin...ll=1#post28169
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  21. #21

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  22. #22

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    OK I had some time today and I did the flush and I installed a new fan clutch. The old clutch was twice as hard to turn as the new one.
    I took the thermostat out a couple weeks ago and added some flush then. I drained the rad and idled the truck until nothing came out then I added 2nd flush and distilled water. It was full at one gallon!? I kept it idling and after a bit drained it pulling the plug all the way never shutting it off and revving it occasionally. Put the plug back in and added more distilled water. after 3 gallons I used the hose and filled drained several times until the foam from the flush went away. The dash gauge was working and temp never went past the first mark. Then I did two more gallons of distilled water. I put a new fitted upper hose & thermostat in, there was no water or coolant to be seen when I opened the housing. I started it up and added a gallon of 50/50. I let it idle and went to do stuff. It died while I was watering the garden and I restarted it when I was done watering, but it did not seem to need any more coolant?! The temp gauge was up to almost halfway after I put the thermostat in. I felt the air in the heater and it was not as warm as it should be, barely as warm as it is outside. I stuck my fingers in the box and it was much hotter to the touch on some parts and on the passenger side even hotter to the touch like I expected the air to be. ??? It was not too hot to hold onto as I would expect it to be.

    The heater not making the air hot bothers me as does the fact that it only takes about a gallon of liquid in the radiator when specs say it should take 9 quarts or 2-1/4 gallons. I expect there to be residual liquid in the engine but 5 quarts!?

    I also put in a new distributor today. The coil is a few months old. She idles nice now with the new carb. I used geezers ear tune method revved it and turned the dist until it was on the edge of missing and pulled it back a tick. I did that before I started doing the flush.

  23. #23



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    If you drive it around and get it hot. Feel the front of the radiator. It should feel about the same temp all around. If it has any cold spots it might be plugged. You can also use one of them point and shoot temp testers. It should be running around 195 to 210
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  24. #24

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    Half way on the temp gauge is normal. You have to realize that the heater blowers in these things aren't super efficient to start off with. Maybe the blower motor is tired, the seals have perished allowing air to flow around the core instead of through it, a control flap isn't closing properly... Also if the core is gunked up it won't heat all the air passing through it - some of the core surface area will be 'dead'. Pulling the heater unit out of a Gen 1 isn't too bad but it will give you the opportunity to replace the heater hoses and really sort out the heater. I had the luxury of being able to pull mine out and chemically flush the core and generally recondition the whole thing. 30+ years of sediment and flakes of iron from the block had plugged it up pretty badly.

  25. #25

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    OK. I drove it with the bed full to the lower brim of fist sized and larger concrete chunks. When I got to the dump about 8 miles. I took the temp with a point and and shoot. It was all over the place on the front of the fins. The top near the inlet was 140ish and there was a hot spot near the exit. When I got home I felt the fins whil;e it was still running and it was cool to the touch. I pointed the gauge at the top tank and it was 160. The thermostat housing was 180 and the metal pipe out of the WP was 180 but the WP right next to it was only 160?
    Anyway I think this means Geezer is correct about the heater core. I don't recall if I mentioned it but the whole box is a new to me pull from the junkyard. I put it in a couple years ago and haven't been driving or worrying about it enough top take notice until now. I expect I'll take it out and soak it in vinegar and see what that does for it. If that don't work they still have cores on RA.

    Off topic- I put in a new reverse switch this morning but when I hooked it up the reverse lights stay on regardless of what gear it is in. I tried it both ways, reversing where the two wires were plugged into the wire tail that goes up to the harness. ?? I recall a thread in the shout box about a ball bearing but the tip on this thing did depress so I am unsure if that would be the reason. It worked fine until I removed the old one when I replaced the throwout bearing a few years ago.

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