Volvo Penta Thermostat Housing Cover O-Ring 3858938
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
Volvo Penta 3858938 is a genuine OEM O-ring used in select Volvo Penta sealing applications. Current active parts listings consistently identify it as an original Volvo Penta O-ring, and the strongest application language available links it to thermostat-housing service associated with a flat cover plate, making it a practical replacement whenever that sealing point is opened during cooling-system work.
Key Features
- Genuine Volvo Penta OEM part number 3858938.
- Commonly described as an O-ring for thermostat housing service.
- Associated with a flat cover plate style sealing location.
- Current cross-reference listings also associate this part with reference number 3588638.
Engine Compatibility
The strongest supportable application detail reviewed points to thermostat-housing use rather than a broad engine-family claim. Because current listings do not provide a clean, model-by-model OEM fitment breakdown in the visible source text, the safest compatibility language is to treat 3858938 as a thermostat-housing sealing O-ring that should be matched to the correct Volvo Penta parts schematic and serial-specific application before ordering.
Serial Number Fitment Notice
Volvo Penta sealing parts can vary by engine version, housing design, and production break. Match part number 3858938 to your engine serial number and the correct thermostat or cooling-system parts diagram before ordering to confirm the exact sealing location.
When This Part Needs Replacement
Replace this O-ring anytime the related thermostat housing or cover plate is removed for service, or when the original seal shows flattening, hardening, cracking, swelling, or signs of coolant seepage. Replacing the seal during reassembly is usually the better choice than reusing an older compressed O-ring.
Installation Notes
Install on a clean sealing surface and compare the old O-ring carefully against the new OEM part before assembly. A light coat of the appropriate assembly lubricant or clean coolant can help prevent pinching during installation. Avoid twisting, over-stretching, or reusing an aged seal in a thermostat-housing application.
Alternate/Superseded Part Numbers
Current reviewed sources continue to list 3858938 as the active Volvo Penta OEM number. Related cross-reference listings also show 3588638 in connection with this part number for reference purposes.
Parts Desk Insight
With small thermostat-housing O-rings, the easy mistake is reusing the old seal because it still looks acceptable on the bench. In practice, replacing it while the housing is already apart is usually the cheaper move than reopening the same job for a minor seep later.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.