CHRYSLER 52028974AA CAP ASSY
Product Specifications
Product quality
OEM Equivalent Grade
Wholesale price USD
$1.16
Wholesale price CNY
¥7.8
bolt MOQ (Minimal order)
350 pcs
local_shipping Production time
10-60 days
package_2 Shipping Weight:
—
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Application (cross references) 6
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| CHRYSLER | 52028974AA |
| CHRYSLER | 4596198 |
| CHRYSLER | 55116897AA |
| CHRYSLER | 04596198 |
| CHRYSLER | 04592098 |
| CHRYSLER | 05278697AA |
Overview & Operating Principle
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The CAP ASSY is the engine oil filler cap — a bayonet-lock or quarter-turn threaded closure assembly fitted to the valve cover or cam cover oil filler neck that seals the engine's lubrication system against oil leakage, contamination ingress, and uncontrolled crankcase pressure venting during normal engine operation. The cap performs three simultaneous functions: it seals the filler neck opening against oil splash from the valve train and cam chain lubrication circuit, preventing oil from escaping from the filler aperture during operation when the engine's rapid cam rotation generates oil mist and pressure pulses inside the valve cover; it prevents atmospheric dust, water, and debris from entering the lubrication system through the filler opening; and on engines where the positive crankcase ventilation circuit connects to the valve cover, the cap's internal seal also maintains the slight negative pressure on the crankcase side of the PCV system — a cap that does not seal correctly admits unmetered atmospheric air into the crankcase, altering the PCV circuit's pressure balance and causing the ECU to register a lean mixture condition from the unmetered air entering the intake. The cap body is typically injection-moulded from glass-filled polypropylene or polyamide with a moulded rubber O-ring or lip seal at the seating face that compresses against the filler neck's sealing surface when the cap is rotated to its locked position, providing oil-tight sealing without requiring a torque tool.
This unit — CHRYSLER 52028974AA — is manufactured to OEM-equivalent specifications: outer diameter and bayonet or thread profile for the filler neck engagement, O-ring or face seal diameter and compound for oil resistance and sealing, cap body height and grip geometry, any integrated oil separator or baffle feature for splash management, and colour and labelling per the OEM design are matched to the original part. Supplied as a direct replacement for standard fitment. Available wholesale from 1.16 USD, MOQ
Oil filler caps fail through O-ring hardening and cracking from heat cycling and oil exposure that prevents the seal from conforming to the filler neck face, producing an oil leak or an air leak at the cap-to-neck interface; through bayonet lug fracture from overtightening or from impact damage that prevents the cap from locking into its closed position; and through cap body cracking from underbonnet heat that causes the polypropylene to embrittle and fracture at the lug positions. A cap that is lost, left off after an oil check, or incorrectly seated is one of the most common causes of engine bay oil contamination — a missing cap allows oil mist to spray from the filler neck onto the engine block, exhaust manifold, and accessory belt within minutes of startup.
Symptoms & Diagnostics
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Oil mist or oily residue on the valve cover surface around the filler neck — wet oily film extending radially from the cap base — with the cap confirmed fully seated and locked — the cap's O-ring has hardened and is no longer conforming to the filler neck sealing face; crankcase pressure pulses from the running engine are pushing oil past the hardened seal on every pressure spike; remove the cap and inspect the O-ring — a serviceable O-ring is soft and resilient when compressed; a failed O-ring is hard, flat, or cracked.
Lean mixture fault codes P0171 or P0174 combined with rough idle on an engine with a confirmed intact intake duct and no other obvious air leak source — the oil filler cap O-ring has failed and the cap is admitting unmetered air into the crankcase; the PCV system draws this unmetered air into the intake manifold downstream of the MAF sensor, leaning the mixture; confirm by temporarily sealing the filler neck with a clean cloth while the engine idles — if the idle stabilises and the lean trim reduces, the cap is the air leak source.
Oil filler cap that will not lock into the closed position — the cap can be placed on the neck but rotates freely without engaging the bayonet detent — a bayonet lug has fractured inside the cap body; the fractured lug may not be visible externally; the cap appears to be correctly positioned but is not sealed; this is a significant fault — an unsealed cap allows oil splash to exit the filler neck during operation; replace immediately.
Engine oil level dropping faster than expected with no visible external leak and no combustion oil burning (no blue smoke) — oil is escaping as mist through a poorly sealing filler cap on every engine pressure pulse; the mist escapes to the engine bay and evaporates or burns off the exhaust manifold without forming a visible puddle; the oil loss is gradual and may only become apparent after several thousand kilometres; confirm by placing a white cloth over the filler area and running the engine briefly — oil mist staining on the cloth confirms cap-to-neck seal failure.
Cracked or visibly damaged cap body — cracks visible at the lug positions or across the grip ribs — on inspection — a structurally compromised cap body cannot maintain the O-ring compression required for sealing; even a hairline crack in the cap body at a lug position will allow the lug to deflect under the spring-back force of the compressed O-ring, reducing the sealing load below the minimum required for oil containment; replace on discovery of any visible cap body damage.
Oil on the accessory drive belt or on the alternator or power steering pump housing — an oily smear extending from the engine top toward the belt drive — the filler cap was left off or incorrectly seated after an oil check; oil mist from the open filler neck has been deposited on adjacent components by the underbonnet airflow; oil contamination of the accessory belt causes glazing and belt slip audible as a squeal under electrical load; replace the cap and inspect the belt condition before the vehicle is returned to service.
Logistics & Customs
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International HS Code
3926.90
EAEU Customs Code (TN VED)
3926 90 970 9
Typical Net Weight
Country of Manufacture
China
Standard MOQ
350 pcs
Production Lead Time
10-60 days
Always verify the exact 8-digit or 10-digit subheading with your customs broker for the destination country, as tariff schedules and duty rates vary by jurisdiction.
Installation Tips
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- Clean the filler neck sealing face before fitting the new cap — wipe the top face of the filler neck with a lint-free cloth to remove oil film, dried sludge deposits, and any rubber fragments from the old cap's O-ring; a contaminated sealing face prevents the new cap's O-ring from making complete circumferential contact, producing an immediate oil seep at the cap base; inspect the filler neck face for corrosion ridges or cracks that would prevent a complete seal — a damaged filler neck requires valve cover replacement.
- Confirm the new cap's O-ring is correctly seated in its groove before installation — the O-ring must sit uniformly in the cap's seating groove around the full circumference with no section rolled out of position or pinched; an O-ring that is twisted or partially displaced will be cut by the filler neck edge during cap installation, immediately destroying the seal; press the O-ring uniformly into its groove with a clean finger before presenting the cap to the neck.
- Install the cap by aligning the bayonet lugs with the neck's entry slots, pressing firmly downward, and rotating to the locked detent position — the cap must be pressed down against the O-ring's resistance before it can be rotated to the lock position; a cap that rotates easily without pressing effort has not compressed the O-ring against the sealing face; confirm the cap is at the locked detent by feeling for the positive click and attempting to rotate further — a locked cap cannot be rotated further without pressing downward to disengage the detent.
- Never apply thread lock compound, gasket sealant, or grease to the cap O-ring or the filler neck — the bayonet design provides the correct sealing force through the O-ring compression at the locked position without requiring any additional sealant; grease on the O-ring reduces its friction against the neck face and may allow the cap to vibrate loose; sealant bonds the cap permanently and prevents future oil level checks.
- After installation, run the engine for 5 minutes and inspect the cap base for any oil seep — with the engine at idle, wipe the filler neck base completely dry and observe for 2 minutes; any fresh oil migration past the cap-to-neck interface confirms an unsealed joint requiring cap removal, O-ring inspection, and reinstallation with correct pressing and locking technique.
- Install the new CAP ASSY (CHRYSLER 52028974AA), confirm the locked detent engagement, start the engine and confirm no oil seep at the cap base at idle, clear any stored lean mixture fault codes with an OBD-II scanner if the failed cap was producing an air leak fault, and verify idle quality is stable before returning the vehicle to service.
Tools: lint-free cloth for neck cleaning, OBD-II scanner for lean mixture fault code clearance where applicable. No special tools required for cap installation on standard bayonet designs.
Frequently Asked Questions
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Can an oil filler cap be a source of significant lean mixture fault codes, and how is this confirmed before replacing the MAF sensor or injectors?
Yes — a failed oil filler cap O-ring is a frequently overlooked source of lean mixture codes that leads to unnecessary replacement of more expensive components. The oil filler cap sits directly in the valve cover, which is connected to the crankcase through the engine's internal passages; on engines where the PCV system is routed from the valve cover to the intake manifold, any air entering through a failed cap-to-neck seal is drawn directly into the intake stream downstream of the MAF sensor as unmetered air. The confirmation test is straightforward: with the engine idling and the long-term fuel trim confirmed at a positive lean correction, temporarily cover the filler neck with a clean cloth pressed firmly against the sealing face; if the idle immediately smooths and the short-term fuel trim begins to reduce toward zero, the cap is confirmed as the air leak source. This test takes 30 seconds and costs nothing — it should be the first step in any lean mixture diagnosis before investigating MAF sensors, lambda sensors, vacuum lines, or injectors. ok.parts supplies oil filler caps at wholesale MOQ from 1.16 USD per unit.
How often should the oil filler cap O-ring be inspected and the cap replaced as preventive maintenance?
The oil filler cap O-ring should be inspected at every oil change by removing the cap and squeezing the O-ring between finger and thumb — a serviceable O-ring is soft and elastic and springs back immediately when released; a degraded O-ring is hard, flat, or cracked and does not spring back. Replacement is indicated when the O-ring shows any hardening, cracking, or permanent compression set. As a mileage guideline, cap replacement every 60,000–80,000 km is appropriate for vehicles in normal service; engines in high-heat environments — turbocharged, track use, or towing — should have the cap inspected more frequently as the elevated underbonnet temperature accelerates O-ring degradation. The replacement cost of a filler cap is negligible; replacing it proactively at every second oil change on high-mileage vehicles eliminates any risk of the lean mixture and oil contamination problems that a failed cap produces.
How does the OEM-equivalent aftermarket unit compare to the genuine OEM part?
OEM-equivalent units in this catalogue replicate the current OEM design geometry and material specification. Quality is verified against OEM cross-reference data. When ordering in bulk, confirm with our team that the specification matches the latest OEM revision for your application.
Is white-label or custom packaging available for wholesale orders?
Yes. ok.parts works directly with the manufacturing facility and can accommodate neutral white-label packaging or fully branded packaging with your company logo, part numbers, and barcode. Minimum order quantities and lead times for custom packaging may differ from standard stock. Contact the team via the inquiry form to discuss your specific requirements.
Frequently Replaced Together
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| Part | Reason for Combined Replacement |
|---|---|
| PCV Valve and Breather Hose OEM ref. varies by engine | A failed oil filler cap that has been admitting atmospheric air into the crankcase alters the pressure differential across the PCV valve, causing it to operate outside its designed flow range on every engine cycle. A PCV valve that has been subjected to abnormal pressure cycling may have a fatigued diaphragm that produces the same unmetered air symptoms as the failed cap even after the cap is replaced. Inspect and replace the PCV valve and breather hose simultaneously with the cap if lean mixture codes persist after cap replacement. |
| Valve Cover Gasket OEM ref. varies by engine | An oil filler cap that has been leaking oil indicates elevated crankcase pressure that exceeds the cap seal's capacity — the same pressure that forced oil past the cap may also have been forcing oil past the valve cover gasket. Inspect the valve cover gasket perimeter for oil seeping under the cover edge simultaneously with cap replacement; a valve cover gasket that shows oil migration requires replacement alongside the new cap to restore complete valve cover sealing. |
| Engine Oil and Filter Grade and specification per OEM requirement | Cap replacement that follows discovery of excessive oil loss from cap seepage or misting provides the opportunity to check the oil level and condition simultaneously. If the oil level has dropped significantly from the cap leak, top up with fresh oil of the correct specification — do not top up with a different grade than the current fill as mixing grades alters the lubricant's viscosity and additive package concentration. If the oil is discoloured or shows significant contamination from atmospheric ingress through the failed cap, a complete oil and filter change is recommended. |