I have a 1999 Crown Vic. (90K Mi), I’ve owned her for two years, that overheated after a monumental snow storm this past February. The day before car was running for about two hours in my parking spot while I shoveled out of the mess. Traffic was very slow the next day and I put a heavy load on engine going up hill after about half an hour ride when overheating occurred, analog display shot up from normal operating temperatures of 1/3 to 1/2 way up to overheat and symbol lit up (not flashing) . I found a safe place and pulled over.
Coolant level was fine, no leaking antifreeze, system seem pressurized, upper & lower radiator hoses felt hot so I believe coolant is circulating OK, and fan was blowing when car was overheating. I figured day after huge storm AAA would take too long to tow me so I sit with car for an hour or so then drive home, running a little rough so thinking fail safe may have kicked on alternating cylinder operation although the check engine light didn’t light up nor did overheat symbol flash.
Inspected car, nothing seems wrong & can’t get car to overheat again. I’m thinking ice or snow was blocking radiator or thermostat shot or frozen or something. Drive car normally, about 20 miles each way to/from work, city then highway, with traffic for about half an hour forty minutes each day without recurrence until a couple weeks ago.
After 20 minutes on ride home on highway I hit traffic, car overheats, display shoots up from normal operating temperatures of 1/3 to 1/2 way up to overheat and symbol lights up (not flashing), I immediately cranked the heat, temperature gauge drops a little so symbol not lit up I pull over, open hood see fan motor running high speed, no apparent leaks so I shut off car, wait an hour and limp home again.
I replaced the thermostat, let car warm up to 1/2 way on gauge but radiator fan not engaging, coolant flows when car given gas. Turn on A/C to max cooling and fan kicks on for about 6 seconds and turns off and doesn’t come on again. Coolant looked dirty so I bring to a service station the next day who flushed the radiator. I told them about fan not turning on I believe they pressure tested system and he told me they jumped fan motor which went on but blew a fuse which he replaced, no cost.
I replace the cooling fan relay & 30 amp cooling fan relay fuse. The fuse they put in had a solid aluminum casing which I couldn’t tell if it was blown and fuse was 3 - 4 bucks. I run car till temperature gauge gets to 1/2 way mark but radiator fan not engaging. I’m now thinking fan motor may be bad. This P71 came from an auction in Florida three years ago, I’ve owned her for the last two years and from maintenance records I see car was driven for several years, then last five years in service had about 1000 miles a year on it until sold at auction so fan motor may have had lots of use idling in Florida heat.
Drive car to work every day till next paycheck but car overheats on highway, after hitting slow moving traffic jam so I call AAA and get towed home last nine miles or so. I am convinced I figured this out so next day I replace fan motor, check pigtails which were not oxidized and wires didn’t look burned, run engine till 1/2 way up gauge but fan motor not kicking on, turn A/C to max & nothing. Check 30 amp fuse which is blown so I replace it. Rinse, repeat and same result motor not engaging now but fuse did not blow. Which brings me to today.
I don’t have a volt meter to check relay and could probably figure out how to jump fan motor to check but I’m at the point where I may just figure out how to connect toggle switch to radiator fan and manually switch on when needed.
I think the only thing I haven’t replaced is the coolant sensor by the thermostat but I don’t think that’s the problem. I am hoping I haven’t replaced a part with a defective part or somehow caused more of a problem. I have researched on line forums, manuals and videos before each replacement and believe I did a good job replacing parts and that all replacement parts are good. I have worked on my past cars so I’m not too green.
Should I bring this to a dealer or mechanic to run electrical or computer diagnostic tests? Is that something they do? I don’t have unlimited funds to have a dealership start replacing coolant system piece by piece and thought I could do this without too much trouble but I am stumped.
I am hoping this is something someone has heard of before and can help with. Sorry for the long history.