1998-2002 Subaru Forester Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 1998-2002 Subaru Forester takes fresh DOT 3 or DOT 4 brake fluid that meets FMVSS No. 116, straight from a sealed container. Subaru's Forester schedule calls for replacing the fluid every 30,000 miles or 30 months, and on a first-generation Forester that is now more than twenty years old, an overdue flush is one of the cheapest ways to get a firmer, safer pedal back.

What Brake Fluid the 1998-2002 Forester Uses

The owner's manuals for both the 1998 and 1999 Forester list the recommended brake fluid as "FMVSS No. 116, fresh DOT 3 or 4 brake fluid" and tell owners to use only fluid from a sealed container. The first-generation Forester kept the same basic hydraulic layout through 2002, so DOT 3 or DOT 4 is the fluid to plan on across the run. Check the cap on your reservoir and your own owner's manual to confirm for your exact car.

FMVSS 116 is the federal standard that defines the DOT grades. The difference between DOT 3 and DOT 4 is mainly heat tolerance, both when the fluid is new and after it has picked up moisture:

DOT 4 gives you more margin on long mountain descents or when towing a small trailer, which is why many Forester owners choose it at flush time. Do not use silicone DOT 5. It is a different chemistry from the glycol-based DOT 3 and DOT 4 the system was built around, and Subaru does not list it.

The manual is also clear on a few handling rules: never mix different brands of brake fluid, keep dirt out of the reservoir when topping off, and do not splash fluid on paint or rubber parts, because the alcohol in the fluid can damage them. Wear eye protection; brake fluid is harmful to eyes.

Flush Interval and Why It Matters on an Older Forester

Subaru's published Forester schedule lists brake fluid replacement every 30,000 miles or 30 months, whichever comes first. Maintenance guides for the 1999 Forester place brake fluid replacement at the 30,000 and 60,000 mile services, noting that by 30,000 miles the fluid is losing effectiveness. If you drive in a humid climate or a lot of hill country, lean toward the short side of that interval. Your original maintenance booklet is the final word on the exact schedule for your model year.

The reason for the interval is moisture. The Forester owner's manual warns that brake fluid absorbs moisture from the air, and that absorbed moisture can cause a dangerous loss of braking performance. The federal standard makes the same point on every bottle: keep the container clean and tightly closed to prevent moisture absorption. Look at the table above: wet DOT 3 only has to boil above 140 C, far below its dry rating. Once water gets into the fluid, hard stops can boil it inside the calipers and give you a pedal that sinks toward the floor.

Moisture also causes internal corrosion. On a 1998-2002 Forester, old fluid is a common reason for sticking caliper pistons, pitted master cylinder bores and rusty brake lines. If you do not know when the fluid was last changed on a used Forester, assume it is due now.

Signs Your Forester's Brake Fluid Needs Attention

• Dark fluid. Fresh DOT 3 and DOT 4 is clear to light amber. Brown or black fluid in the reservoir has been in service too long.
• Soft or spongy pedal, especially after repeated stops or a long downhill run, which points to moisture or air in the lines.
• Falling reservoir level. Some drop is normal as pads wear, but the manual says a car that needs frequent refilling may have a leak. Check the calipers, hoses, lines and the master cylinder.
• Brake warning light on the dash with the parking brake released can mean the level is low.
• A dragging wheel or pull to one side, often caused by a caliper piston corroded by wet fluid.

The owner's manual says to check the level monthly. Read the level on the outside of the translucent reservoir on top of the master cylinder against the MIN and MAX marks, and if it is below MIN, top off to MAX with the correct fluid.

How to Flush the Brake Fluid

A flush is a moderate DIY job with basic tools: a line wrench for the bleeder screws, clear tubing, a catch bottle, and a helper or a one-person bleeder. Plan on more fluid than a simple top-off would suggest, because you want to push old fluid out until clean fluid appears at each wheel.

1. Remove as much old fluid from the reservoir as you can and refill it with fresh fluid from a sealed bottle.
2. Bleed each wheel in the order given in the factory service manual, keeping the reservoir above MIN the whole time so no air is drawn into the master cylinder.
3. At each wheel, keep bleeding until the fluid in the tube runs clear and free of bubbles.
4. Tighten the bleeders to the value in the factory service manual; do not overtighten, since old bleeders on a Forester of this age can snap.
5. Top off to MAX, check for a firm pedal before moving the car, then road test at low speed.

On ABS-equipped Foresters, a normal pressure bleed or two-person bleed flushes the lines, but if air got into the ABS unit (for example after the reservoir was run dry), the factory procedure may call for a scan tool to cycle the ABS hydraulic unit. If the pedal stays soft after a careful bleed, have the system checked rather than driving on it.

If a bleeder screw is seized or rounded, that is usually the time to replace the caliper rather than fight it. Our replacement brake calipers and brake hardware kits cover that part of the job.

What to Replace While You Are In There

A flush is a good time to inspect everything the fluid touches:

• Rubber brake hoses. Cracks, bulges or a hose that has swollen inside can cause a pull or a soft pedal. Replace original hoses with new brake hoses.
• Hard lines. First-generation Foresters in salt states often have rusted lines. Scale or weeping at a fitting means replace, using brake lines.
• Master cylinder. A pedal that slowly sinks under steady pressure with no external leak points to worn internal seals. See master cylinders.
• Pads and rotors. The manual notes the Forester's disc brakes have audible wear indicators that scrape when the pads near their limit. If you hear it, fix it before the rotors are damaged. Browse brake pads and brake rotors.

If you do install new pads, the manual's break-in advice is simple: at 30 to 40 mph, apply the brakes lightly, and repeat five or more times.

Frequently Asked Questions

Can I use DOT 4 in a 1999 Subaru Forester that has DOT 3 in it?

Yes. The owner's manual lists DOT 3 or DOT 4. Both are glycol based and compatible, but the manual says not to mix brands, so the cleanest approach is a complete flush to one fresh fluid rather than topping off with a different product.

How often should I change the brake fluid on a 1998-2002 Forester?

Every 30,000 miles or 30 months, whichever comes first, per Subaru's Forester schedule. Go sooner in humid or mountainous driving, and flush right away if the fluid is dark or the service history is unknown.

Can I use DOT 5 brake fluid in my Forester?

No. DOT 5 is silicone based and is not the fluid Subaru specifies. Stick with DOT 3 or DOT 4.

Why does my Forester's brake pedal feel soft after a long downhill?

Old fluid that has absorbed moisture has a much lower boiling point, so heavy braking can boil it and create vapor in the calipers. A fluid flush, and possibly DOT 4 for its higher boiling point, usually cures it. If it persists, check pads, hoses and the master cylinder.

Does a manual-transmission Forester have its own clutch fluid?

Yes. The manual covers a separate clutch fluid reservoir with the same moisture warnings. It is worth bleeding the clutch hydraulics when you flush the brakes if the clutch pedal feels inconsistent.

Sources

1. Subaru 1999 Forester Owner's Manual, Recommended Brake Fluid - FMVSS No. 116 DOT 3 or 4, sealed container
2. Subaru 1998 Forester Owner's Manual, Brake Fluid - same DOT 3 or 4 spec, MIN and MAX level check
3. Subaru 1999 Forester Owner's Manual, Brake Fluid checks - monthly check, moisture warning, no brand mixing, leak warning
4. Subaru 1999 Forester Owner's Manual, Brake Pad Replacement - wear indicators and break-in procedure
5. 49 CFR 571.116 (FMVSS 116), Cornell LII - DOT 3, 4 and 5 dry and wet boiling points, container moisture warning
6. Patriot Subaru, Forester maintenance schedule - brake fluid every 30,000 miles or 30 months
7. Kelley Blue Book, 1999 Subaru Forester maintenance schedules - brake fluid at 30,000 and 60,000 mile services