Is coolant reservoir cap profitable to sell on Amazon United States?

The niche generates $73K/yr across 89 tracked products. 0 of 15 products launched in the last 360 days are still selling. 90-day search growth is -10.1%. Flapen's verdict: Worth a look (55/100).

How competitive is the coolant reservoir cap niche?

61 brands and 148 sellers compete. The top 5 products take 22% of clicks and top 5 brands hold 35% of demand.

What do buyers complain about in coolant reservoir cap?

Top complaints mined from reviews: Size-Overall, Compatibility-Overall, Quality-Overall. The return rate is 2.8%.

When does demand for coolant reservoir cap peak?

Demand is steady year-round — the busiest month runs 1.1× the quietest.

What does it cost to enter the coolant reservoir cap niche?

Listings span $3.08–$20.38; the average listing price is $8.59 (sweet spot $15–$100). The average incumbent carries 264 reviews — the moat a new listing must climb.

coolant reservoir cap

Worth a look

Shows no brand lock-in (top 5 brands take 35% of clicks), but a small market ($73K/yr) keeps it on the watch list.

Brand share

Incredible35%

top-5 brand share — no brand owns this niche

Competition

Great22%

top-5 click share — an open shelf

Review moat

Great264.25

avg incumbent reviews — the moat a new listing must climb

Quality gap

Great4.3★

avg incumbent rating — lower means beatable quality

Conversion

Good5.3%

search→purchase rate — share of searches ending in a sale

Returns

Good2.8%

return rate — above 5% kills the launch gate

Price range

Okay$3.08–$20.38

cheapest to priciest tracked listing — scored on the share inside $15–$100

Avg price

Bad$8.59

avg listing price — sweet spot $15–$100

Growth

Bad-10.1%

90-day search growth — must beat 0% to launch

Market size

Bad$73K

$73K/yr · 162K searches

Signals No Dominant Brand

According to Flapen's Amazon United States niche tracking, coolant reservoir cap is a $73K/yr Amazon United States market (162K searches/yr). The top 5 brands hold 35% of demand. Verdict: Worth a look — 55/100.

Data updated Jul 9, 2026 · scored weekly · How we score niches

coolant reservoir cap market data

Units sold / yr: 10K–13K; avg 100–250/product
Revenue / yr: $86K–$107K; units × avg price
Conversion rate: 5.3%
Avg BSR: #2,353
Page quality: 0%
Prime: 100%
Sponsored: 56%
Out of stock: 0.8%
Avg brand age: 32 months
Avg seller age: 160 days

Competition & brand share

Clicks spread well past the top 5 (22% combined) — an open shelf where new products get seen.

Brands

61 rising

Sellers

148

Top-5 brand share

35%

Top 20: 74%

Top-5 click share

22%

Top 20: 57%

Open market

61%

Dorman13%
ACDelco7%
ROVIKE5%
KEVWR5%
SWQS4%
DeFageH4%

Demand & seasonality

Weekly Amazon search volume, last 104 weeks — -10.1% search growth over the last 90 days.

No pronounced peak months · busiest ÷ quietest = 1.1×

Open Trend

Top coolant reservoir cap search terms

coolant reservoir cap68K/yr -7.0%4.6% conv.
coolant cap30K/yr -17.3%4.5% conv.
coolant cap replacement11K/yr -12.0%5.1% conv.
coolant reservoir tank cap12K/yr -1.9%5.0% conv.
reservoir cap10K/yr -15.2%2.7% conv.
radiator reservoir cap8K/yr -20.7%5.9% conv.
coolant overflow cap5K/yr +32.0%4.0% conv.
radiator overflow cap4K/yr +10.4%4.7% conv.
engine coolant reservoir cap4K/yr -2.9%4.7% conv.
coolant tank cap4K/yr -7.2%4.3% conv.

All search terms

Top coolant reservoir cap products on Amazon

Each bubble is one product — market share against review moat; bubble size tracks estimated sales, color grades how beatable the incumbent looks.

Beatable (≤4.3★) Contested Strong incumbent (>4.7★)

All 24 tracked products in this niche — three views at once, no toggling.

Top sellers

by 90-day click share

Dorman 54201 Engine Coolant Reservoir Cap Compatible with Select Models

Dorman$12.424.6★4,822 rev

2PCS Engine Radiator Coolant Water Tank Black Reservoir Cap Compatible with Infiniti Nissan Renault OEM# 21712-79900

KEVWR$6.264.4★385 rev

DeFageH 2Pcs Coolant Reservoir Cap - Premium Leak-Proof Coolant Caps for OEM# 21712-79900 Compatible with Nissan Pathfinder Maxima Murano Infiniti G35

DeFageH$4.374.6★26 rev

13502353 Coolant Reservoir Cap for Chevy GMC Buick Cadillac -Silverado 1500 2500 3500 Express Avalanche Suburban Captiva Cavalier Equinox Malibu Savana Sierra Yukon Radiator Surge Tank Cap

ROVIKE$11.524.4★162 rev

Car Radiator Cap Replacement OEM#68442532aa 53479332 Coolant Reservoir Cap Compatible with Chrysler Dodge Jeep Ram Standard Car Accessories Radiator Cover Easy to Mounting

Stacool$7.204.5★84 rev

Newest

by launch date

4PCS Coolant Reservoir Cap Replacement OEM# 21712-79900 - Radiator Overflow Coolant Reservoir Tank Cap Compatible with Nissan Murano Rogue Versa Quest & Infiniti EX35 FX37 G35 M35

Alfaly$3.0811 rev

4mo ago

DeFageH 2Pcs Coolant Reservoir Cap - Premium Leak-Proof Coolant Caps for OEM# 21712-79900 Compatible with Nissan Pathfinder Maxima Murano Infiniti G35

DeFageH$4.3726 rev

5mo ago

Houlishu 2 Pack Coolant Reservoir Cap Replacement Universal Radiator Reservoir Cap Compatible with OEM# 21712-79900 Black Overflow Tank Cover for Water & Antifreeze

houlishu$6.0918 rev

5mo ago

SWQS Coolant Reservoir Tank Cap for Toyota Engine Coolant Expansion Tank Cap 16471-0A030 Radiator Coolant Caps Replacement for Toyota Sienna 2004-2010 Lexus RX330 2004-2006 & RX350 2007-2009 (Black)

SWQS$9.932 rev

7mo ago

HZEL Car Coolant Reservoir Cap Vehicle Radiator Surge Tank Cap OEM# 13502353 13598760 1305248 Automotive Replacement Accessories Compatibility with Encore Regal Verano

HZEL$5.7816 rev

10mo ago

What buyers say about coolant reservoir cap

What buyers praise and complain about, mined from review topics.

What buyers love

Size-Overall55%

“Fit great”

Quality-Overall13%

“Quality replacement”

Value For Money7%

“Good price”

Advertised Vs Actual Product5%

“Worked as advertised”

Coolant4%

“Worked great as direct replacement for coolant reserve tank fill cap”

Efficiency4%

“Does the job just fine”

Leak-Proof2%

“No leaks so far”

Assembly/Installation1%

“Easy installation”

Durability1%

“durable”

Ease Of Use1%

“Easy to use”

What buyers complain about

Size-Overall23%

“Doesnt fit advertised to fit”

Compatibility-Overall14%

“Did not fit Suzuki Kizashi”

Quality-Overall11%

“Expected much higher quality from Gates”

Durability8%

“Not durable”

Coolant7%

“Stop coolant loss”

Functionality-Overall5%

“doesnt fix”

Leak-Proof4%

“Will leak everywhere”

Advertised Vs Actual Product3%

“Do not believe what is advertised”

Value For Money3%

“absolute waste of money”

Pressure3%

“It doesnt hold pressure”

Top return reasons

Size-Overall53%

Coolant22%

Compatibility-Overall10%

Advertised Vs Actual Product3%

Defective Material/Parts3%

Pressure2%

Value For Money2%

Functionality-Overall1%

Leak-Proof1%

Product Condition1%

Common questions

Is coolant reservoir cap profitable to sell on Amazon United States?: The niche generates $73K/yr across 89 tracked products. 0 of 15 products launched in the last 360 days are still selling. 90-day search growth is -10.1%. Flapen's verdict: Worth a look (55/100).
How competitive is the coolant reservoir cap niche?: 61 brands and 148 sellers compete. The top 5 products take 22% of clicks and top 5 brands hold 35% of demand.
What do buyers complain about in coolant reservoir cap?: Top complaints mined from reviews: Size-Overall, Compatibility-Overall, Quality-Overall. The return rate is 2.8%.
When does demand for coolant reservoir cap peak?: Demand is steady year-round — the busiest month runs 1.1× the quietest.
What does it cost to enter the coolant reservoir cap niche?: Listings span $3.08–$20.38; the average listing price is $8.59 (sweet spot $15–$100). The average incumbent carries 264 reviews — the moat a new listing must climb.