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HT4100 4.1, 4.5, 4.9 Discussion, Cooling Problems in Cadillac Engine Technical Discussion; Replace The Bcm ( Body Control Module) With A Same Year From A Wrecking Yard. Could Be The Whole Problem! ...
  1. #16
    carnut is offline Cadillac Owners Master
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    Re: Cooling Problems

    Replace The Bcm ( Body Control Module) With A Same Year From A Wrecking Yard. Could Be The Whole Problem! No Signals From The Bcm Could Cause Late, Short Fan Operation. The Fans Do Not Work If The Key Is Off. Disconnect The Battery Prior To Bcm Replacement. The Fan That Maintains Coolant Temperature Does Not Turn On Till Approx. 220 Degrees, Lowering The Thermostat Will Only Delay Or Not Allow The Fan To Function.

  2. #17
    Night Wolf's Avatar
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    Re: Cooling Problems

    Carnut.... I was wondering, what is the reason why you capitalize the first letter in every word?...kinda makes it annoying to read after a while....

  3. #18
    Hot4.1 is offline Cadillac Owners Member
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    Re: Cooling Problems

    Sounds like good news. Where is the BCM located on an 86 Fleetwood FWD 4.1?

    Also, where can I get useful manuals? (wiring diagrams, technical stuff - I know how to change oil .... well, maybe not!!!).

  4. #19
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    Re: Cooling Problems

    Acutually, the ECM controlls the fan in relation to coolant temp. The BCM only controlls the fan in relation to the A/C.

  5. #20
    Hot4.1 is offline Cadillac Owners Member
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    Re: Cooling Problems

    The alternator is only putting out 11.8 volts now. I think I will swap it first. That may have something to do with the ECM/BCM being dead.

    I now understand about the air pocket and false coolant level in the radiator. As soon as I get a buddy to help me, I will fill it to the brim and put in the BarsLeaks Gold. I will keep the 195 thermostat. I now understand that late model cars are designed to run hot for emissions control. All my cars have been 70s or earlier - mostly Olds. I have 5 kids and keep them boated in.

    The A/C compressor is bad - not sure if somebody disconnected it.

    I once had a '59 CoupeDeVille and a 64 Fleetwood. I loved those cars.

  6. #21
    carnut is offline Cadillac Owners Master
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    Re: Cooling Problems

    I do not capitalize every first letter. I lock on the caps lock and then type. Once sent to the forum, it changes to every first letter as it posts. I'm not the best typist so I thought less chance of a mistake with the caps lock button on. I didn't realize it would modify as it posted. If we are going to be picky about form then I will try to mis spell most of my words as most others do. please understand that my responses are to help less knowlegable people with concerns that I have had first hand experience with. This is voluntary on my part! I will, from now on, try to refrain from upsetting you.

  7. #22
    Hot4.1 is offline Cadillac Owners Member
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    Re: Cooling Problems

    Carnut,

    You have probably saved me a couple $thousand, so you can type in braille as far as I am concerned.

    Happy New Year

  8. #23
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    Lightbulb Re: Cooling Problems

    Quote Originally Posted by carnut
    Proper Thermostat Is 195 Degrees. Putting In A Lower Temp One Will Not Allow The Engine To Go Into Closed Loop At The Proper Time, Causing Poor Fuel Mileage. The Fans Turn On At Approx. 220 Degrees. Using The Wrong Thermostat Will Delay Or Keep The Fans From Ever Coming On. I Don't Approve Of Patch Jobs Like By Passing Sensors. Will Cause Other Problems. Diagnose It Right And Fix It Right. One Fan Reacts To Engine Temp. The Other To Head Pressure In The A/c System. This Engine Easily Gets Air Pockets In It Which Will Give A False Fluid Level In The Radiator. Start With A Cold Engine After Proper Thermostat Installed To Fill The Radiator. Set The Climate Control To Auto And 90 Degrees. Fill The Radiator At Normal Idle, When The Upper Hose Just Starts To Get Warm, Have A Buddy Raise The Idle Manually To Approx 1500 Rpm, Continue To Fill The Radiator While The Engine Speed Is High, That Will Help Purge The Air. Once The Radiator Is Full Reinstall A New Proper Radiator Cap While At Hi Engine Speed. Then Fill The Recovery Tank To Correct Hot Level. If The Fans, Fan Control Modules And Related Sensors Are Good, The Engine Temp Should Stabilize At About 195 To 200 Degrees. Correct Engine Temperature Is Mandatory For The Other Sensors To Work Within Thier Parameters. Knowing How To Monitor The System Thru The Dash Diagnostics Is Very Important. I Would Recommend A Factory Service Manual. Money Well Spent. Hope This Helps A Bit, Bill.
    Now I see why the fans in my 85 De Ville stoped working when I changed the thermostat to a cooler one last summer. Going to chang back to the proper temp ASAP. Thanks for the good tech info, EVEN if you do use caps lock .

  9. #24
    Hot4.1 is offline Cadillac Owners Member
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    Thumbs up Re: Cooling Problems

    I put on the new alternator. I got a Chiltons and radiator cap. Put in the Bars Leaks - 2 vials for V8. The wife revved the engine while I topped off the radiator. The ALTERNATOR DIDN'T CHARGE!!!


    The Chiltons wiring diagram showed mini-fuse #7 going to fan controls. I wiggled it and the DASH INDICATORS LIT UP!!!! I wiggled all of them. The alternator now charges and the RADIATOR FANS COME ON. Ran through the computer codes and now can't find the code page.

    The wife's got a mall buggy!

    Thanks for the patience and advice. I just bid on a service manual on Ebay.

    Where are the codes?

    Thanks for saving me a couple $thou.

  10. #25
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    Re: Cooling Problems

    Hey if your alternator acts weird again, make shure to check that the fan belt that feeds the waterpump pulley from the bottom flywheel is not slipping. it happened to me a couple months ago on my 83 fleetwood and drove me nuts after awhile. finally after a week of diagnosing the whole charging system somebody on this forum told me what I had overlooked. it was so simple, but it I was not looking for the obvious.

    so keep that in mind if you ever have problems with low charging alternator again. that one belt feeds both the water pump and by default your alternator.

    Hope I save you some grief !

    mine would work well somtimes, and then not other times, It's enought to drive you batty

  11. #26
    carnut is offline Cadillac Owners Master
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    Re: Cooling Problems

    That only works on the ht4100 engine that has multiple belts. As I recommended before, the alternator belt will slip if the smog pump belt is worn out or loose. glad I could help, Bill.

  12. #27
    Hot4.1 is offline Cadillac Owners Member
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    Re: Cooling Problems

    OK, so, if the HT4100 has multiple belts, my 4.1 FWD 86 Fleetwood is not a HT4100. It has one serpentine belt.

    Where can I get a trunk lock that matches my door key?


    It failed inspection. NOX and HC (catalytic converter?). O2 sensor reads 128 (perfect). Any suggestions?

  13. #28
    carnut is offline Cadillac Owners Master
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    Re: Cooling Problems

    Sorry I wasn't clear enough. The 82 to 85 Eldos and sevilles with the ht 4100 and the rear wheel drive fleetwood broughams used multible belts. All other 4100's were mounted sideways in the engine bay and used a serpentine belt. The slipping smog pump belt that affects alternator charging is related to the multible belt cars mentioned above.

  14. #29
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    Re: Cooling Problems

    OH well I learn something new every day! Not being very fond of front wheel drive cars I did not know that. Oh well I tried

  15. #30
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    Re: Cooling Problems

    There is a lot of misinformation here.....LOL

    Hot4.1....that car can run thru Death Valley in 115 degree heat and idle in it forever with the AC on. I know because I have done it many times. If it is operating the way it was designed it will work fine. Spend your time and money diagnosting what is wrong with the car rather than trying to re-engineer it. It is not necessary to re-engineer it. Hundreds of thousands of those cars ran perfectly fine and never over heated the way it was designed....

    Why is it overheating. Seems simple but..if the fans come on and the engine continues to climb in temp then something else is wrong...not the fans. If the engine continues to climb in temp until it overheats and the fans never turn on then check into the fans. First step.

    Doesn't that car have a fan controller module mounted beside the ran shroud?? Follow the large wires from the fans to the fan controller. Possibly that is what is failed. The ECM on that car controls the fans I believe. Whether it is the BCM or the ECM , the fans are controlled by only one. Coolant temp and the AC request (AC compressor possible) govern the operation of the fans.

    Putting a colder thermostat in an engine will not cure overheating. Whether the stat opens at 160 or 195 either is open when the engine gets hot enough to boil...putting a colder stat in will not add cooling capacity.

    If you wired the fans hot all the time....are they wired correctly and blowing the right direction...?? Not to be too stupid here, but, something tells me that those fans were wired for a "hot ground" In other words, the fans are fed 12 volts and pulled to ground thru the fan controller. If you put 12 volts to the fan controlller terminal of the fan motor it will run backwards and try to blow the air thru the radiator forward. This will cause overheating. IF you have the fans wired hot make SURE which way the air is blowing. I know this sounds stupid...but...I have seen cars that were miswired during development that people put their hands behind the radiator and SWORE that the fans were blowing correctly (pulling air thru the grill) and they were actually running backwards. Run the fans and hold a piece of paper behind them (a dollar bill works great) to make sure which way the fans are blowing.

    If there is an aftermarket water pump on the engine it is suspect. The OEM water pump impeller cannot fall off the shaft but I have heard/seen two different aftermarket (cheaper) water pumps for the 4.1/4.5/4.9 that came off overheating engines and the water pump impeller had fallen off the shaft so the pump was not pumping. You might want to check this.

    If the water is moving and the system is full and the thermostat is opening correctly (not failed) the engine will cool fine. You just need to stop replacing parts or trying to re-engineer it and do some basic diagnosis. If correct, the system will cool fine and will idle in the worst traffic with the AC on almost indefinitely.

    Some other simple things...have you pressure tested the cooling system and the pressure cap with a pump up style tester that you can borrow or rent from many auto parts stores? Have you checked the coolant concentration to make positively sure it is 50/50 green conventional coolant/distilled water. If the cap is correct at 15 PSI, the coolant is 50/50 the system will not boil until it gets to 265 F. This is fact. If it is boiling sooner then the system is not holding pressure or the coolant is not the correct ratio.

    Is the radiator full and staying full? That engine uses a rad cap with the pressure release to the coolant recovery bottle and a drop valve in the center of the cap to allow coolant back into the radiator from the coolant recovery bottle when the system cools down. Always check the system when cold. Open the rad cap and the coolant should be right up to the neck of the cap...no air space allowed. If there is an air gap to the cap and the coolant recovery bottle is full then the cap is not working correctly and the sytem has air in it that will cause overheating.

    Fill the cooling system completely full cold and start the engine with the cap off. Watch the coolant for bubbling and/or false boiling. If there is a lot of bubbling/boiling when not hot then that is a sign that a head gasket is leaking compression into the coolant system and the head gaskets will need to be repaired.

    Lots of things to check, here....

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