help with 1999 v6 mustang heater/cooling system problem

Discussion in 'The "Other" Bench' started by N360LL, Jan 28, 2019.

  1. N360LL

    N360LL milehi71Stage1

    The problem; heater doesn't put out heat like it should

    Symptoms: If the cooling system is fulled and burped the heater will work as it should on that drive. As temperature and pressure increase the coolant is put into the overflow bottle. But it does not return to the radiator as the temperature and pressure drop.

    Parts and procedures thus far; radiator cap, coolant bypass tube assembly, flow restrictor in outlet side of heater core, HVAC head unit. Cleaned out the overflow bottle to see if the passage that the return hose connects to was plugged(it's not). I have had the heater flushed and pressure tested separately from the rest of the heating system. The cooling system hold pressure when using the the pressure testing kit (it will hold 18 psi and cap is 16 lbs) and the burping process goes as it should. Front of car raised so that the vent port is the highest point in the system.

    What am I missing or what is else could it be?

    P.S. In the past few years I have replaced the radiator, thermostat and upper radiator hose. These is no sign of coolant in the oil either. This even has a couple of Ford Master Technicians puzzled at the moment.

    Thanks in advance for the assistance
  2. Quick Buick

    Quick Buick Arlington Wa

    The H core is plugged,,Disconnect the H hoses from motor. Run water from garden hose through them both ways.
  3. johnriv67

    johnriv67 Well-Known Member

    If that’s right I’ll be impressed. Ford master tech, we shall see
  4. Quick Buick

    Quick Buick Arlington Wa

    thats because the car is older than the techs.
    mrolds69 likes this.
  5. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Ive taken more than a few fords of that vintage apart to find the impeller on the water pump to be no good. The fins were rotted away. The big symptom was no heat. It was amazing that the engine wasn't overheating. The water pump would barely move the coolant.
  6. telriv

    telriv Well-Known Member

    In my career I can't count or remember how many heater cores I back flushed. Fords are not the ONLY ONES that rot out impeller blades MANY OEM's do it, but it's mainly du to lack of maintenance.
  7. Quick Buick

    Quick Buick Arlington Wa

    The impeller blades go to **** because the radiator is not grounded on the American car/truck..
    Water antifreeze cavitates at above 3000 rpms and becomes electrically charged and eats up the blades on the water pump, radiators,,Heater cores.

    Side note. I got no idea how fast or long a after market aluminum rad will hold up to that kind of punishment....

    On SBC And BBC I usually put a marine water pump on the car or truck. stainless impeller.

    Another thing to do is put a ground lug on the radiator, &&&&&& If you don't care about appearance put a tee pipe on your manifold fitted with a sacrificial zink plug.. Zink that chunk of metal thats on the back of a boat.. Sacrificial Anode Radiator Cap.pdf
    I just found the cap I have never saw this product till now... I claim no responsablity
    Last edited: Jan 28, 2019
  8. Footbag

    Footbag Well-Known Member

    I have to ask about that replaced radiator that you mention. Was it a OEM replacement or a aftermarket one? Also did it come with a radiator cap or did you use your old one? My 03 V6 did that same thing you described and all i had to do was spend a little extra time correctly burping the coolant out of the three points in the system. If you wanna check flow from pump all you need to do is loosen the top burping lug on the high side that goes into the back of the engine bay. If pump is working good that will push a lot of coolant out when opened. Ask me how my antifreeze shower went finding that out lol.

    As for the coolant overflow tank. The lever in the tank will raise when hot and lower when cool. I got air into my system when the tank did not have enough coolant in it when it was stone cold. The Radiator cap i believe will control that flow up and down.

    BUICKRAT Torque Rules!

    Possible head gasket, but check water pump impeller first.
  10. N360LL

    N360LL milehi71Stage1

    Update. Had a conversation with a different Ford Master Tech and he thinks it's the 3.8L V6 head gasket issue. A list of related items to be discusses later. But for now the next step is a compression test to see if his theory is correct. That would be that the head gasket(s) are leaking coolant into the combustion chamber and the engine is burning it. I knew this was a possibility but didn't want to go there until had to. There is also a way to test the "air" in the cooling system by using a kit from NAPA. I will investigate that as well.

    To answer the other questions; Aftermarket radiator, heater core is flowing coolant in and out, new Motorcraft radiator cap, water pump is working correctly ( a shower of coolant sprays all over if you leave the vent plug out of the bypass tube stand pipe and start the engine).

    I have found a couple of TSB's about the symptoms of head gasket failure in the past couple of days. When I get time I will see if those are helpful.

    New info; supposedly, the engine has had the head gaskets replaced twice already. I'm suspicious given the amount of oil and gunk on the outside of the engine that I can see, but if that is indeed the case then it would make me wonder if the process was done correctly and if the mating surfaces are flat. If not then the question becomes how much time and money do I spend to fix a $1000 car. This could be a dark hole to throw money into with no upside. I have put way more money in this car that it's worth already, maybe it's time to stop fixing this car.
  11. buick64203

    buick64203 Right wing conservative Staff Member

    Sometimes with a bad head gasket, when you start the engine up cold, the cooling system builds up pressure immediately. Something you can check for. They also sell a block tester. Its a turkey baster looking thing that you fill with a liquid. You test the antifreeze and if there are hydrocarbons present, the liquid reacts and changes color.

    I hear you on the $1000 car comment. You can probably pick up a good running GT with a stick for a little more
  12. pbr400

    pbr400 68GS400

    Years ago my parents had a new Cadillac that developed a heat loss and overheating issue while under warranty (‘82 Coupe deVille, 4.1 v6). Twice the dealer ‘fixed’ it. The third time it occurred (out of warranty) my dad took it to the local guy who said ‘she’s full of ‘stopleak’! You’ve prolly got a blown head gasket, they’ve just been patching it.’ No telling what the dealer billed GM for...
  13. buick64203

    buick64203 Right wing conservative Staff Member

    Oh God...those 4.1's were absolute junk! Notorious for coolant leaks, head gasket issues and bad camshafts. That's why they call the GM coolant tablets "Cadillac pills" to this day
  14. pbr400

    pbr400 68GS400

    ^^No, ours was the ‘credit delete’ Buick 4.1 4bbl v6! Dad ordered the car and was wary of the Caddy v8 after the division’s V8-6-4 debacle. So, our Caddy was very pretty, but slow when not broken. It had a complete rear end failure and numerous electrical problems, too-but it was a beautiful car when sitting on the shoulder with the hood up!
  15. buick64203

    buick64203 Right wing conservative Staff Member

    V6, I didn't catch that! Last of the big Caddys.
  16. N360LL

    N360LL milehi71Stage1

    Funny you mention the 4.1L V8. I once got a 1986 from a family friend because I got it running. It cost me $12. My dad and I did a lot more work to it than that over the next few years to keep it running before it was time to move on, but a distributor cap and rotor was all it took to get it away from the front of the guys house. I don't miss that car one bit.
  17. 1973gs

    1973gs Well-Known Member

    You are getting air in the system somehow. You state that it works after you first fill and bleed the system. That tells me that the heater core is not plugged. I'm not familiar with Mustangs, I've been a GM technician most of my life. Before you start tearing the engine apart, make sure that your hose clamps aren't allowing air to be sucked in as the car cools. Get rid of all of the worm gear clamps and install tension clamps like all of the manufactures use now. They maintain a constant and correct tension on the hose and won't allow air to be sucked in as the engine cools. This could account for the coolant not being sucked back into the engine from the overflow tank. Also, make sure that there is no corrosion on the fittings that your hoses go on. If there is corrosion, no clamp will seal. Also, aluminum radiators should not be grounded. They need to be isolated from the body. By grounding the radiator, if there is any electrical voltage in the cooling system, current will flow through the radiator and corrode it. Use a volt meter connected between the negative battery terminal and the coolant in the radiator. If you have more than .1v, there's a problem. You need to do this with the engine off and with it running. You should also turn components on and off while measuring voltage. If the voltage increases as you turn something on, check the ground on that component. Make sure that all engine/chassis ground are good. The most common cause of high voltage in the cooling system is old, dirty coolant or corrosion in the engine from not changing the coolant often enough.

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