Head gasket failure on the 1998 Subaru Legacy
When head gasket failure gets reported
Owners of the 1998 Subaru Legacy report head gasket failure at a median of 110,000 miles. A quarter of the reports come in before 100,000 miles and a quarter after 125,000 miles, from 8 reports that carried an odometer reading.
A part like this is normally expected to survive 115,000 miles. It is the 4th most-reported problem on this model year.
The mileage distribution
The reported range runs from 80,000 miles at the tenth percentile to 145,000 miles at the ninetieth, a spread of 64,526 miles across the middle 80% of reports.
A spread this wide points at use rather than design. Towing, climate, service history and city mileage all move a failure like this, so the median is a weak guide to any individual car.
0% of the dated reports were filed under 36,000 miles.
The whole distribution
| 10th | 25th | Median | 75th | 90th |
|---|---|---|---|---|
| 81,274 miles | 100,000 miles | 108,048 miles | 126,000 miles | 145,800 miles |
Read the 10th percentile as “one report in ten arrived this early”. Exact figures are shown in this table because it is the table of record; everywhere else on the site they are rounded to the precision the sample can carry.
What a percentile can and cannot tell you here
These five numbers describe the readings owners gave, in order. The median is the middle one: half the reports arrived below it. The 10th and 90th are the edges of the bulk of the distribution, and the distance between them is the part worth reading. A tight spread — say 70,000 to 95,000 miles — points at something that wears out on a schedule, and the schedule is knowable. A wide one, 20,000 to 190,000, points at a fault that hits some cars and never troubles others, which means the mileage on the listing in front of you tells you very little about your odds.
What these figures are not is a survival curve. Every reading here comes from a car whose owner filed a complaint, so the sample contains only failures: it cannot say what share of the fleet made it past 150,000 miles untouched, because those owners had nothing to report. Nor is the mileage the moment of failure — it is the odometer reading as recalled at the time of filing, which may be weeks later and is sometimes rounded to the nearest ten thousand by the person typing it.
Percentiles are shown at all only once 8 readings exist for the vehicle and mode. Below that the middle of a handful of numbers is noise wearing a decimal point, so the figures are withheld rather than dressed up.
What happens, and what it costs
Putting it right typically runs $1,400–$4,000 at an independent US shop. That range is an editorial estimate held in this site's failure-mode catalogue, not a figure from NHTSA, and it is a repair cost rather than a diagnosis cost.
This mode is classified as critical, which means a failure can leave the car unable to stop, steer, or stay out of the way of traffic. It is weighted accordingly in the risk score.
The same failure on other years
The same failure is reported on 6 model years of this car. It shows up earliest on the 2003, at a median of 75,000 miles, and latest on the 2002 at 110,000 miles.
By volume the 1998 is the worst of them, which makes this a problem of this specific year rather than of the model as a whole.
If one year stands out to the left, that is the year to avoid; if the whole line sits at a similar mileage, this is wear rather than a defect in one production run.
Tick median reported mileage Solid middle half of reports Faint 10th to 90th percentile Colour how bad the failure is when it happens
What owners wrote
Verbatim from NHTSA complaint narratives, trimmed for length. The mileage is the one the owner gave.
Vehicle was leaking ant freeze, which was splashing all over the engine compartment. This resulted in the temperature gauge reading hot. This occurred because the head gasket blew out, and was replaced. *ak
While driving 60 MPH vehicle stalled. Consumer was unable to restart vehicle. It was towed to a garage for inspection, and mechanic determined that the head gasket needed to be replaced due to a blow out. *ak updated 02/24/06
Car overheated, took to dealership. Called next day and informed the head gasket was blown. After discussing, they said they had to replace both head gaskets. Knowing about cars, this seemed strange to me that both were blown at same time - it was at this time that dealership pointed out to me that subaru is having problems with head gaskets and that this is not an ususual problem. Replacement cost was $2200.
Also reported on the 1998 Subaru Legacy
Other body or interior problem
Excessive oil consumption
Other engine problem
Other speed control problem
Alternator or charging system failure
Master cylinder or brake booster failure
How far this goes
Complaints are voluntary, so 9 is a floor and not a count of affected cars. Mileages are typed in by owners and cluster on round numbers. And the mode itself is assigned by software reading the complaint text, which is reliable in bulk and fallible one report at a time.
Questions this page answers
At what mileage does head gasket failure happen on the 1998 Subaru Legacy?
Across 8 owner reports that included an odometer reading, half were filed by 110,000 miles. A quarter were filed before 100,000 miles and a quarter after 125,000 miles. These are the mileages owners reported when they complained, not a prediction for any individual car.
How common is head gasket failure on the 1998 Subaru Legacy?
9 reports have been filed with NHTSA, about 0.1 per 1,000 vehicles. Complaints are voluntary, so this is a floor rather than a count of affected cars.
What this is and is not. These are the mileages at which owners chose to complain to a federal agency, which is not the same as the mileage at which the part fails on every car. It skews toward failures that happened outside warranty, cost real money, or frightened someone. It is still the only public dataset that carries failure mileage at all, and the shape of a few hundred readings is informative even when a single one is not. Methodology · JSON · this failure on other cars
Source Owner complaints and recall records published by the US National Highway Traffic Safety Administration, model years 1996–2027 Figures rebuilt Published by AtWhatMileage How every figure is computed