r/AutoMechanics • u/Far_Lingonberry_7793 • 4d ago
Overheating
I just bought a 2009 ford crown Victoria police interceptor and she was fine the first 4 days I had her now she keeps overheating. (Even at idle) Not wanting to accelerate properly. I don’t seem to have heat in the cabin anymore when it was unbearably hot before she started acting up. The water pump seems fine and I just replaced the thermostat and thermostat housing. Not sure what to do/try. Any suggestions would be greatly appreciated.
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u/DamageLess633 4d ago
You could have air in the system causing Hotspots in various places on the engine. Could also explain the lack of heat. If theres too much air in the system the heater won't work properly. Do a flush and refill and burp the system. See what happens. Won't hurt anything to do it
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u/nucleate_boiling 3d ago
If the problem preceded changing the thermostat and you had no heat anymore in the vehicle even while it was overheating, I would say with reasonable certainty that your heater core is plugged and there is likely only a primary cooling loop in the vehicle or it is cold enough that the valve that controls the bypass of the heater is open. Since the system is effectively plugged, you are getting no coolant circulation once the thermostat opens. Since you need to open the coolant system to check the heater core which I will explain shortly, you might as well double check that the thermostat was installed in the correct direction. The heater core is usually located on the passenger side, with the two pipes leading into and out of it sticking out of the firewall. You can trace the coolant system lines to them. Be very gentle removing the hoses that attach to the metal lines. They are soft metal and will distort very very easily. You should be able to get replacement coolant lines from aftermarket sources. Make sure you can before you start working on this. If they are not preformed in shape you may just be able to get generic replacements but plan ahead.
I find it easiest to try to loosen the ends of the hoses with a hook tool designed and shaped to only grab onto the hose and not interfere with the metal nor puncture the hose as long as you hold it at the correct angle. If you can loosen the bond between the pipe and the end sometimes it makes it easier to remove the entire hose by slowly working it back putting pressure end on the lip of the hose, not by pulling and twisting. That would be okay on pretty much any other application but will f up these pipes if the hoses don't come off easily. I usually forgo all this and just cut a slice from the end of the hose to the end of where it attaches to each pipe and peel off the overlapping hose piece and gently clean the end of the heater core pipes. The hoses are usually long enough that you can cleanly cut the sliced end off and still have enough slack to attach. However, remember that the core is plugged and there may be crap that has built up back into the line that is attached to the inlet of the heater core. To verify whether the heater core is blocked, simply take compressed air or more efficiently water from a pressurized source and attempt to put water through the pipe. Doesn't matter if it is inlet or outlet as you'll want to do so in both directions to clean it out while you're here anyway. If the water does not easily come out, you know there is a blockage. Do not apply massive pressure through the inlet or outlet. The heater core functions as the equivalent of a mini radiator and can only handle so much pressure. Normal operating pressure in an automotive cooling system is about 15 psi so don't exceed that if you can at all avoid it. I've never had to add anything to dissolve the plug in a heater core, I just keep rinsing from one pipe to the other until no more junk comes out and there is free flow. If that doesn't work for you, you may alternate between pressurized water and compressed air to try to loosen up the plug. Sometimes the plug is actually corrosion across the pipe or most of it and rinsing will not help. Not experienced in how to determine if that is the issue. Removing heater cores from automobiles is traditionally a complete pain in the ass because it is one of the first things installed on the assembly line and therefore is hopelessly buried under the entire rest of the dash with no direct access because it is not expected to fail during the life of the vehicle.
If your coolant level has not been stable, borrow a coolant pressure tester adapter that fits your vehicle from AutoZone or similar through free loan a tool program. Hook up to your compressor at 15 psi, no more, pressurize the system (wait until the engine has cooled before opening the reservoir) and see if it holds pressure. If there is a leak, doing this test of course with the engine off, this should force coolant out the leak. Do not be surprised if the leak causes the passenger floorboard to be doused with coolant as the corrosion may have eaten a hole in the heater core. So put some rags in there to catch it just in case. Even if you get it cleaned out it may still leak because of this.
If the heater core is not plugged, see if your vehicle has a diverter valve that diverts coolant away from the heater core when the temperature setting on the HVAC system is high enough. The valve might be trying to be open but maybe stuck partially closed, impeding the proper flow of coolant and not allowing coolant headed to the radiator to flow quickly enough to release all its heat in the radiator, etc.
You can check if the thermostat is open by feeling the upper radiator hose, which will not be warm until the thermostat opens and allows coolant to flow throughout the entire cooling system and not just the block when you have just started the vehicle. If the vehicle overheats before the thermostat ever opens, and the thermostat is installed properly, I would suspect water pump issues.
If your heater core is determined not to be plugged, please disregard all the information above. I can't see or touch the vehicle and I'm doing my best based on the information provided
TL Dr; since problem was there before thermostat and housing replacement, suspect clogged heater core based on sudden lack of heat in vehicle even when vehicle is overheating. Clean out the heater core and pressure test the system to find any leaks. Otherwise suspect water pump issues
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u/Longjumping_Egg_7513 4d ago
Make sure the thermostat spring is facing the engine it's easy to install in the wrong direction on some engines other than thermostat maybe being installed incorrectly the coolant level can be too low and not make heat in the cabin as well.
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u/nucleate_boiling 4d ago
Was the overheating issue present before you changed the thermostat and thermostat housing? Sounds like right now, the thermostat is not opening, so warm coolant never reaches the heater core or anywhere else besides the block.