1999 Mercury Grand Marquis Problems

What owners report

Owners of this model year most often report a cracked plastic intake manifold on the 4.6L V8, which leaks coolant and is followed by overheating, misfires and stalling, and often appears from roughly 50,000 to 120,000 miles. A second common theme is intermittent loss of headlights and dash lights, which several owners link to the lighting control module, and worn front-end steering parts such as tie rod ends are reported at various mileages.

1. 1
   Engine cooling

   Cracked plastic intake manifold / coolant leak

   Mentioned in 27 of 60 sampled complaints

   Complaints describe the plastic intake manifold cracking near the thermostat housing or coolant crossover, often with no warning. Coolant then leaks onto the engine, producing steam, a sweet smell, overheating, low coolant, misfires, rough idle and stalling; several owners say the engine had to be shut down and the car towed. According to the complaints, dealers and independent shops diagnosed a cracked manifold and quoted replacement, and some owners say the dealer declined assistance or said the coverage period had passed. Reported across a wide range, from about 52,000 to 190,000 miles, with many reports between roughly 60,000 and 130,000 miles.

   3 related service bulletins

   What to check: Before buying, check the coolant level and look for crusty residue or dampness around the thermostat housing and manifold, and ask whether the manifold has been replaced and with which part. A service bulletin in this file describes an extended coverage program for the composite intake manifold, so ask whether that program applied to this vehicle.

   2 excerpts from owner complaints in NHTSA records

   “Cracked the air intake on my 1999 Mercury Grand Marquis. It was made out of cheap plastic. I had to step on the throttle to get out of the way, and my car started steaming. Come to find out, the intake manifold cracked. It's only $300 for the part, not including labor.”

   NHTSA complaint #10377186, filed 2011-01, 120,000 miles

   “I had to fix the leak 3 times. Finally, my mechanic noticed the crack on the intake manifold. It is made of hard plastic! What in the world anyone would design such part in plastic? How can such material sustain extreme heat for long periods of time. I purchased new one and it is plastic again with a little improvement. But it is mostly plastic again. I believe this is service scam. You make parts to only last 4 years and make money from selling auto parts. …”

   NHTSA complaint #10070748, filed 2004-01, 67,000 miles
2. 2
   Exterior lighting

   Headlights and dash lights cut out intermittently

   Mentioned in 10 of 60 sampled complaints

   Owners describe headlights, dash lights, turn signals and hazards switching off intermittently while driving, sometimes for a few seconds and sometimes not returning at all. Several reports say the problem appears after 20 to 45 minutes of driving, in rain or cold, or with the high beams on, and some mention a failing lighting control module behind the dash. Complaints also note that on this model year the dealer diagnosed the control module but the vehicle was not repaired, with one owner told the part was no longer manufactured. Mostly reported between roughly 100,000 and 160,000 miles, often on longer drives or after the lights have been on for a while.

   What to check: Run the headlights on high beam for an extended period, including over bumps, and watch for flickering or dropouts; ask whether the lighting control module or headlight switch has been replaced. Some owners note that a later-model recall for this symptom exists, so ask whether any related program or repair has been done.

   2 excerpts from owner complaints in NHTSA records

   “My headlights, hazards, and turn signals all just randomly went out while driving. They have not come back on since. After reading forums I believe it to be the lcm but my year model is not included in the recall. I believe this issue dates back farther than 2000 and ford should step up and recall more of these lcm components.”

   NHTSA complaint #11340109, filed 2020-07, 160,000 miles

   “Vehicle was parked. I went to turn my headlights on. No headlights, turn signals, dash lights, hazard flashers or dome light. The 2003-2005 models were recalled for this same thing with the lcm failing. Please look into this as this is a serious safety issue.”

   NHTSA complaint #11102426, filed 2018-06, 155,000 miles
3. 3
   Steering

   Front tie rod ends detach or wear out

   Mentioned in 6 of 60 sampled complaints

   Complaints describe front tie rod ends separating or being found badly worn, in some cases during low-speed parking or backing out of a driveway, leaving the steering unable to turn the wheels. Owners say the removed ends could not be greased and appeared to have been assembled without grease, and that dealers replaced inner and outer tie rod ends and adjuster sleeves. One owner also reports the idler arm separating from the steering linkage while driving. Reported from about 54,000 to 155,000 miles, with several reports near 90,000 to 103,000 miles at low speed or during parking maneuvers.

   What to check: Have a mechanic inspect the front tie rod ends and idler arm for play and check whether the joints have grease fittings or prior replacement records. Ask for a front-end inspection as part of any pre-purchase check on this model year.

   2 excerpts from owner complaints in NHTSA records

   “While driving pins in steering coulm became losse and caused car to shut off while at stop light had to tow to service shop; had found common ford issue with loose steering pins in 1999 Mercury Grand Marquis should be recall very dangerous to happen to some cast is $300 plus tax and tow I feel ford ouwes me to this that built this car not me its cost as much as a decent used car to day I would like ford to offfer me help; with there past issues with cars”

   NHTSA complaint #11278876, filed 2019-11, 154,850 miles

   “While parking at a low speed, the front right tie rod fell off. The consumer had the vehicle towed. The dealership repaired the tie rod. ...other tie rod on left side was about to fall off and the other two were badly worn. No place to grease, so it mudt be life time.”

   NHTSA complaint #10111383, filed 2005-02, 54,000 miles
4. 4
   Vehicle speed control

   Speed control engagement and surging concerns

   Mentioned in 4 of 60 sampled complaints

   Complaints describe the cruise control failing to disengage when the brakes are applied, the vehicle losing acceleration with the traction control light flashing, and a throttle cable snapping. One owner reports the engine surging and the car moving while still in drive. According to the complaints, dealers charged for diagnosis without duplicating the failure, or told owners repairs would be at their own expense. Reported from roughly 70,000 to 135,000 miles, often while cruising at highway speed or in stop-and-go traffic.

   What to check: Test the cruise control engagement and cancellation, including brake-pedal cancellation, and ask about any prior throttle cable or speed control repairs. Check that the accelerator cable moves freely and returns without sticking.

   2 excerpts from owner complaints in NHTSA records

   “My car was in drive at a business traffic intersection drive way on a slight hill with the brakes on when the engine surged and the car started to reverse while still in drive. I had to put considerable pressure on the brakes to stop it. I checked and the shift lever was still in drive. My car has been properly maintained and was recently serviced with all required services done. This really scared me and I would have crashed into a car if it was behind me. Ford should look into this safety problem.”

   NHTSA complaint #10663813, filed 2014-12, 108,000 miles

   “The contact owns a 1999 Mercury Grand Marquis. While driving 75 MPH with the speed control engaged, the speed increased when the brakes were applied and failed to disengage. The contact was forced to manually disengage the vehicle speed control in order to avoid a crash. The dealer advised the contact to bring the vehicle in to be repaired at his expense. The manufacturer was not notified of the failure. The failure mileage was 97,000. …”

   NHTSA complaint #10422547, filed 2011-08, 97,000 miles

Buying note. This model year draws repeated reports of intake manifold coolant leaks and intermittent lighting failures, so a pre-purchase inspection should focus on the cooling system and the lights. Service records showing manifold replacement, front-end steering work and any lighting module repairs are worth asking for.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Counts refer to that sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.