Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 1999 Mercury Grand Marquis owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 1999 Mercury Grand Marquis. The contact stated that the vehicle had a leaking intake manifold. The vehicle was taken to an independent mechanic and diagnosed that the intake manifold needed to be replaced. The vehicle was not repaired. The dealer and manufacturer were made aware of the failure but informed the contact that there was no recall associated with the VIN. The failure mileage was approximately 120,000.
Intake manifold failed (burned and disintegrated in the area of the thermostat ) and had to be replaced at considerable expense . Presently the speedometer fails intermittently dropping to zero at random moments. Most importantly the lights cut out intermittently usually when the heat is on and on longer trips. Also, most times it has happened when it has been raining and colder. Drove upwards of 40 miles with the headlights cutting out intermittently in the rain and cold, problem has continued to recur but seems to be related possibly to having the heat on. I believe the lighting control module is located near a heating outlet and May be suffering a failure as a result but this is just speculation. Also, previously when I had pulled into a rest area for awhile, after cooling down, the problem went away for a little while then resumed after about ten miles with the heat on. …
Tl* the contact owns a 1999 Mercury Grand Marquis. While the vehicle was parked with the engine running, the contact shifted into reverse and noticed steam coming from the hood. The vehicle was then shifted back into park and turned off the engine. Upon opening the hood, the contact noticed that a part of the manifold was missing the thermostat. The contact was unsure of any warning indicators illuminating. The contact went to bill macdonald Ford (1200 s carney dr, st clair, mi 48079, [phone]) and was informed there were no recalls. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the issue. The failure mileage was approximately 135,000.
Plastic intake manifold failed, antifreeze leaking from around thermostat due to this failure and leaking into coil packs and causing major misfire in motor. Happened suddenly, no indication of leak prior to this failure. Was driving when this happened and had to call for help to get vehicle back home, and now can't drive it . Cost to fix is expensive, and the car ran great until this happened. Sounded like I has thrown a rod, popping louder on exceleration, so I immediately parked it and turned off the motor.
On the 1999 Mercury Grand Marquis ls 4.6 l v8 the original plastic intake manifold cracked and busted wide open causing all the coolant / antifreeze to pour out. From what I gather there was a recall on this years ago and they made a different intake manifold which was aluminum for the part that the thermostat goes into and the rest of it was plastic. If this isn't caught in time and all the fluid leaks out it will completely destroying your engine also. Mine cracked while it was in park just running.
Problem: the car was diagnosed with a leaking head gasket & defective manifold. Cost to repair $2504.80 (I paid it) I brought the car in on 11/17/03 and got it back 11/20/03. I was told the repair was complete. As I drove it off the lot the car shimmied and stalled. The car was brought right back and they still are working on it as of 11/21/03 9 am. History of problem at Ford: Ford has issued the following technical service bulletins for these two problems ( from www.alldata.com ) 03-6-2 mar 03 engine - oil leak from r/h cylinder head gasket 02-1-4 jan 02 engine head gasket - approved replacement procedures 01-21-10 oct 01 engine - oil leaking from head gasket 02-2-2 intake manifold - cross-over channel coolant seepage according to www.lemonaidcars.com ( www.GM-v6lemons.com/mediaattn.htm )the Ford 4.7 liter has had these problems before and caused Ford to extend warranties to 6 yrs./ …
Plastic intake manifold on 4.6 liter engine found to be cracked and leaking coolant. The loss of coolant results in the vehicle becoming disabled and/or unsafe to drive. Leaking coolant is also toxic to children and animals, as they are more likely to be in contact with coolant on the ground or garage floor. This defective part (plastic intake manifold) was identified by Ford motor company as defective and quietly settled in a class action lawsuit. Replacement parts have been redesigned. However, Ford did not contact customers with this model car to notify them of the defective part or to offer resolution. Earlier models of this engine (and all other engines) used a metal intake manifold. These were not problematic. Intake manifolds are not a moving part of the vehicle engine, and are not subject to ware. …
I received noticed of intake manifold on fords passengers cars failure and of the settlement offered to repair and warrant said intake manifold. At that time I owned a 1999 Grand Marquis ls. Before getting said notice I had took my car to landers Ford dealership in jackson,ms hwy 80 west where the intake manifold was repaired by dealership because of failure out of pocket expense cost me $879.00 when I received noticed of lawsuit and or claims on said intakemanifold I returned to that dealership but was turned away with no resolve said dealership went out of business months later never to compensate me for out of pocket expense or giving me extended warranty info.Ford corporate office refuse to help after I explain I had my receipts to said claim and gave me no lead way of what to do.now I am stuck with no warranty no out of pocket cost and the same car needing the same work done again …
While driving, (at any speed)the car's engine shut down several times. Each time I heard a "beep" and warning lights came on- check engine, traction control and ABS. After a minute or so, the engine would start normally. The engine shut down 6 times ! Each time I heard the "beep" and warning lights illuminated including traction control and check engine lights. I was on my way home with my newborn in the car,it just cuts off, and it nearly caused an accident on the highway as many other cars almost ran into me because the car shut off while I was driving on the highway. This is a very dangerous condition, especially as power steering and power brakes are lost on shut-down. I am literally afraid of driving my vehicle as no one knows what is wrong with my vehicle. This needs to be addressed asap as someone could get seriously hurt or killed. …
Driving on the hwy and the car started to overheat with hot steam shooting out from the engine and it also had a strong coolant smell. The car could not be driven until l it had $1,500 in repairs for a known, leaking plastic manifold issue. This failed part cracks and leaks into the hot engine area. And, Ford had redesigned the failed part. Additionally, Ford had once offered free fixes for a few months for police cars and taxi cabs with the same engines under a class action law suit but didn't tell the owners about. Thousands of consumers were ripped off because Ford should have fixed this issue under the class action recall. But they didn't bother notify anyone about the three month recall window. In checking the NHTSA records, there are thousands of us with the same reported problem. Please take some corrective action for us.
NHTSA investigations
Spark plug ejection from cylinder head
On September 6, 2005, odi received a petition requesting that the agency investigate allegations of engine spark plug ejection in certain model year 1997 through 2004 Ford vehicles with triton v-8 and v-10 engines.odi received a total of 474 non-duplicative complaints on the subject vehicles where the complainant, or the dealer repairing the vehicle, reported that a spark plug detached from the cylinder and/or…
Engine complaints in other Grand Marquis years
Frequently asked questions
How common are engine problems on the 1999 Mercury Grand Marquis?
NHTSA has 33 complaints about the engine & cooling of the 1999 Mercury Grand Marquis, 20% of the model year's 164 complaints. The component named most often is exhaust system › manifold/header/muffler/tail pipe (7 mentions).
Is there a recall for 1999 Mercury Grand Marquis engine problems?
No. NHTSA lists no engine & cooling recall for the 1999 Mercury Grand Marquis, though it has 3 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 1999 Mercury Grand Marquis engine problems start?
Half of the complaints with a recorded mileage happened before about 103,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 1 injury to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.