Volvo Penta OEM Heat Exchanger O-Ring 866690 | D4 D6 Cooling System Seal | Supersedes 3583651
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Volvo Penta OEM Heat Exchanger O-Ring — Part 866690
- Part Number: 866690
- Brand: Volvo Penta (Genuine OEM)
- Official Product Type: Heat Exchanger Gaskets & O-Rings — Cooling System O-Ring
- System: Cooling — heat exchanger internal sealing
- Supersedes: 3583651 (earlier Volvo Penta reference)
- Included In: Volvo Penta intake gasket kit 876725 (applicable keel-cooled configurations)
- GTIN / UPC: 745061718265
- Weight: approx. 0.01 kg
Quantity note: Several D4 and D6 heat-exchanger diagrams specify three 866690 O-rings in a single assembly. Check the serial-number-specific schematic before ordering to confirm the correct quantity for your engine — ordering a single O-ring when three are required means reopening the cooling system for one small seal.
What It Does
The 866690 is the genuine Volvo Penta OEM O-ring used to seal internal heat-exchanger components and coolant passages in selected D4 and D6 marine diesel engines. It appears in Volvo Penta heat-exchanger diagrams at internal sealing locations, including keel-cooling configurations, and is the current replacement for the earlier 3583651 in applicable assemblies. Once an O-ring has been compressed and heat-cycled in service, it should not be reused after the assembly is opened — a flattened or hardened O-ring will not reseal reliably.
Compatible Applications
Confirm fitment, location, and required quantity by engine model, serial number, and the specific Volvo Penta heat-exchanger diagram before ordering.
D4 Series
- D4-180I-B, D4-180I-C, D4-180I-D, D4-180I-E
- D4-210A-A, D4-210A-B
- D4-210I-A, D4-210I-B
- D4-225A-B, D4-225A-C, D4-225A-D
- D4-225I-B
D6 Series
- D6-300A-F, D6-300D-F, D6-300I-F
- D6-310A-A
- D6-330A-F, D6-330D-F, D6-330I-F
- D6-370A-F, D6-370D-F, D6-370I-F
- D6-400A-F
- D6-435D-F
Keel-Cooled Configurations
- Selected keel-cooled Volvo Penta diesel installations where the heat-exchanger diagram specifies 866690
Not sure it fits or how many you need? Send us your Volvo Penta engine model and serial number before ordering.
Related Heat Exchanger Assembly Components
Volvo Penta D4 and D6 heat-exchanger diagrams show 866690 alongside the following internal sealing and cover components. Inspect all of them while the heat exchanger is disassembled — these are sold separately and are not included with 866690:
- 3583647 — O-ring
- 3885174 — O-ring
- 3583830 — O-ring
- 3583831 — O-ring
- 3583832 — O-ring
- 947282 — Gasket
- 3583828 — Cover
- 3595407 — End cover
- 876725 — Intake gasket kit (contains 866690; applicable keel-cooled configurations)
Part Numbers & Supersession
- 866690 — Current Volvo Penta OEM part number
- 3583651 — Earlier Volvo Penta reference; superseded by 866690
When to Replace
Replace the heat exchanger O-ring when:
- The heat exchanger is disassembled for any reason
- Coolant seepage is visible around the sealed joint or end cover
- The existing O-ring has flattened, hardened, or taken a set
- The O-ring is cut, swollen, or distorted
- Heat-exchanger cleaning or overhaul requires removal of the sealed components
- Corrosion or contamination is found around the sealing groove or surface
Service Interval
Replace whenever the heat exchanger is opened. Do not reuse an O-ring that has been in service — a heat-cycled O-ring that is removed and refitted will not reseal as reliably as a new seal. Inspect the cooling system for leaks after any heat-exchanger service by running the engine and checking the sealed joints before returning to service. For engines used in saltwater, corrosion around the O-ring groove should be checked and treated at each heat-exchanger service interval.
Installation Notes
- Confirm 866690 is specified at the correct location in the Volvo Penta heat-exchanger diagram for your engine model and serial number, and confirm the required quantity before ordering
- Clean the O-ring groove and all mating surfaces completely before fitting the replacement seal
- Inspect the groove for corrosion, pitting, or distortion — a damaged groove will prevent the new O-ring from sealing correctly
- Compare the replacement O-ring with the removed part before installation to confirm correct sizing
- Inspect adjacent heat-exchanger O-rings and seals while the unit is apart and replace any that show hardening, cracking, or deformation
- Use only the lubricant or assembly compound specified in the Volvo Penta workshop manual for this O-ring location
- Inspect the cooling system carefully for leaks after reassembly before returning the engine to service
Technical FAQ
Q: How many 866690 O-rings does my heat exchanger need?
It depends on the specific engine model, serial number, and cooling configuration. Several D4 and D6 heat-exchanger diagrams specify three 866690 O-rings in a single assembly. Check the serial-number-specific Volvo Penta heat-exchanger schematic before ordering to confirm the correct quantity — if the heat exchanger is already apart, order all required O-rings at once.
Q: What superseded 3583651?
866690 is the current Volvo Penta OEM replacement for the earlier 3583651 reference in applicable heat-exchanger assemblies. If your older parts list or service record shows 3583651, order 866690.
Q: Can I reuse my old O-ring after opening the heat exchanger?
No. An O-ring that has been compressed and heat-cycled in service takes a set and will not reseal as reliably after being disturbed. Replace all heat-exchanger O-rings whenever the assembly is opened.
Q: Is 866690 used in keel-cooled engines as well as standard heat-exchanger engines?
Yes. The 866690 appears in selected keel-cooled Volvo Penta diesel installations in addition to standard heat-exchanger cooling systems. It is also included in the Volvo Penta intake gasket kit 876725 for applicable keel-cooled configurations. Confirm the location and quantity from the diagram for your specific engine.
Parts Desk Insights
The most common mistake with 866690 is ordering a single O-ring when the heat-exchanger diagram calls for three. If the heat exchanger is already apart for service, it is worth pulling the schematic and ordering the full set of O-rings before closing the cooling system — coming back in for one small seal after the engine is back in service costs far more in labour than the O-ring itself. The other thing to watch is the supersession — if an older parts list shows 3583651, that is the same seal under the earlier part number. Order 866690. When the heat exchanger is open, it is also the right time to inspect the adjacent O-rings (3583647, 3885174, 3583830–3583832) and the gasket (947282) — replacing everything that is disturbed at once is standard practice on these cooling systems.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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