Ask Don · 20261005_160000_stant-27277-thermostat-seal-fitment-guide

Stant 27277 Thermostat Seal – Fitment Guide for Buick, Oldsmobile, Pontiac (1986–1991)

Buick, Oldsmobile, Pontiac (1986–1991)

Stant 27277 Engine Coolant Thermostat Seal – from Don's Obsolete Auto Parts

Keep your car or truck on the road with a genuine Stant 27277, the Stant thermostat seal for the 1986–1991 GM 3.8L V6 in Buick Electra, LeSabre, Reatta and Riviera, Oldsmobile Delta 88 / Eighty Eight, Ninety Eight, Toronado and Cutlass Ciera, and Pontiac Bonneville (catalog notes Eng. VIN C or 1-bolt housing on many lines). A thermostat seal is a molded rubber ring that seals the thermostat or the water outlet instead of a flat paper gasket. Stant's description of these seals: no sealer or RTV is needed, and each one is shaped for its application.

Key Features

• Part Number: Stant 27277 (single pack); same seal as Stant 25277 in the Stant catalog
• Type: Engine coolant thermostat / water outlet seal (rubber, molded style per the Gates equivalent)
• Size: about 1.07 in. inside diameter × 1.46 in. outside diameter × 0.105 in. thick (Gates 33610 data for the direct equivalent)
• Cross-references: Gates 33610; Carquest 30983; General Motors 12337901, 25535939; Ideal Tridon 30983; NAPA 1081; Pep Boys 35126; Standard Thomson 1081; Stant equivalents 25277, 30983

Stant's own 1928–1994 application catalog lists the 27277 for 3 makes from 1986 to 1991. It's a good fit for restoration projects, weekend drivers and mechanics keeping older vehicles running.

Compatible Makes & Models (from the Stant catalog)

• Buick (1988–1991): Electra (1988–1990), LeSabre (1988–1991), Reatta (1988–1990), Riviera (1988–1990)
• Oldsmobile (1986–1990): Cutlass Ciera (1986–1988), Delta 88 (1986–1988), Eighty Eight (1989–1990), Ninety Eight (1986–1990), Toronado (1986–1990)
• Pontiac (1988–1991): Bonneville (1988–1991)

Note: Always verify fitment for your specific year, make, model and engine. Some catalog lines are limited to one engine code or housing type; the full engine-by-engine list is in the fitment appendix below. If you have your old seal, compare its size and shape, or just ask Don and Kathy.

Price is $9.95 plus $3.00 for shipping. Don and Kathy offer a fair deal for this. Buying for a club, a shop, or a whole fleet of project cars? Even better.

Why Buy From Don & Kathy at Don's Obsolete Auto Parts? Don Leask founded one of the earliest online obsolete auto parts businesses (carparts2 on eBay in 1997, the second auto parts store on eBay) and grew it to 11,000–17,000 unique listings. Today, with help from their digital agent Misty ([email protected]), Don and Kathy connect directly with restorers and collectors while preserving their legacy of quality parts. These seals come from Don's own shelves.

To reach them, click the "Don & Kathy Leask" button at the bottom left of any page on donsobsoleteautoparts.com, or email [email protected].

The Stant 27277 Thermostat Seal: The Right Seal for Buick and Oldsmobile Owners

Thermostat seals are small, but they decide whether a cooling system stays dry. When the thermostat housing comes off, the right seal is the quiet part that keeps the job from turning into a second trip to the parts counter.

Why This Seal Matters Stant's application catalog covering 1928 through 1994 lists the 27277 across 3 makes (Buick, Oldsmobile, Pontiac). Cross-reference tables tie it to the Stant 25277 and Gates 33610, which makes it easy to match against an old parts list or a worn-out seal.

Real-World Fitment Examples

• 1988–1990 Buick Electra V-6 3.8L
• 1986–1988 Oldsmobile Cutlass Ciera V-6 3.8L
• 1989–1991 Pontiac Bonneville V-6 3.8L

Keeping Older Cars on the Road Don and Kathy Leask have been part of the classic car world since the early days of the internet. Starting with carparts2 on eBay in 1997, they became one of the largest online sellers of obsolete parts. Now, with their Don's Obsolete Auto Parts site and digital agent Misty, they're making hard-to-find parts discoverable again, connecting owners of rare inventory with the enthusiasts who need them.

Buying Tips

• Match three things before ordering: year, model and engine. Watch for catalog notes such as engine VIN codes or housing type.
• Compare sizes: the 27277 is about 1.07 in. inside diameter × 1.46 in. outside diameter × 0.105 in. thick.
• Some engines use a gasket and a seal at the thermostat; check what came off yours.
• Restoration shops, clubs and collectors can ask about quantity pricing.

Fitment appendix — every Stant catalog line for

27277

Source: Stant Thermostats, Gaskets, Caps – 1928 through 1994 (application pages). Format: Model — years [engine: years (catalog notes)]. Catalog coverage ends with 1994 models.

Buick

• Electra — 1988–1990 [V-6 3.8L: 1988–1990]
• LeSabre — 1988–1991 [V-6 3.8L: 1988–1991 (1988: engine VIN code C)]
• Reatta — 1988–1990 [V-6 3.8L: 1988–1990]
• Riviera — 1988–1990 [V-6 3.8L: 1988–1990]

Oldsmobile

• Cutlass Ciera — 1986–1988 [V-6 3.8L: 1986–1988 (1986–1988: with 1-bolt housing)]
• Delta 88 — 1986–1988 [V-6 3.8L: 1986–1988 (1988: engine VIN code C; 1986–1987: with 1-bolt housing)]
• Eighty Eight — 1989–1990 [V-6 3.8L: 1989–1990]
• Ninety Eight — 1986–1990 [V-6 3.8L: 1986–1990 (1986–1987: with 1-bolt housing)]
• Toronado — 1986–1990 [V-6 3.8L: 1986–1990 (1986–1987: with 1-bolt housing)]

Pontiac

• Bonneville — 1988–1991 [V-6 3.8L: 1988–1991 (1988: engine VIN code C)]

Cross-references (full)

• Gates: 33610
• Carquest: 30983
• General Motors: 12337901, 25535939
• Ideal Tridon: 30983
• NAPA: 1081
• Pep Boys: 35126
• Standard Thomson: 1081
• Stant equivalents: 25277, 30983

Sources

1. Stant Thermostats, Gaskets, Caps – 1928 through 1994 catalog (scan on Internet Archive): https://archive.org/details/StantThermostatsGasketsCaps1928Through1994OCR637Pages — part-number index ("Make / Year(s)" table at the back of the catalog) and application pages (PDF pages 322, 324, 326, 329, 541, 543, 544, 546, 547, 551, 573). Every catalog line pairs "Thermostat Seal 25277" with "Thermostat Seal (1 Pack) 27277".
2. PartsHawk – Gates 33610 (interchange lists Stant 27277; style and dimensions): https://partshawk.com/gates-33610-engine-coolant-thermostat-seal.html
3. AutoPartsPrime – Stant 27277 ("Engine Coolant Thermostat Seal"; UPC 033342072770; vehicle list): https://www.autopartsprime.com/stant/engine-coolant-thermostat-seal/mp-27277
4. PartsHawk – Stant 27277 (fitment list): https://partshawk.com/stant-27277-engine-coolant-thermostat-seal.html

Ask Don