PULSCAR ANALYSIS - OWNER COMPLAINTS ABOUT COOLANT FLUSHES AND MAKER DOCUMENTS ON COOLANT SERVICE
PulsCar analysis of NHTSA public data, November 2026.
License: CC BY 4.0
Attribution: "PulsCar analysis of NHTSA public data, November 2026."
Published alongside https://www.pulscar.io/blog/coolant-flush-cost

Scope. Complaints in NHTSA's public file received 1 January 2015 to 4 October 2026 (782,908 records) that mention a coolant flush, drain-and-fill, coolant change or exchange, cooling system service, or wrong or mixed coolant, or a shop recommending one. 605 complaints were found by two searches of the complaint text (the exact phrases are in codebook.txt); 551 of them describe it on the owner's own vehicle. Each complaint was sorted twice by written rules (codebook.txt), and every difference between the two sortings was settled by a written rule. The final category, both sortings and the flags are in the complaints file.

What was counted. Complaints, not vehicles. A complaint is counted in one category (D flush done as the remedy for a stated fault; S flush recommended or quoted; F a service visit or draining found something; P a problem began after a visit that included a flush or change; R routine flush mentioned; U coolant a side detail of another story; M wrong, mixed or crystallizing coolant named as the problem; N not about this vehicle's coolant service). The flags shop_recommended_flush and came_back_or_persisted count only complaints where both sortings said yes, so they are minimums.

Owner-reported prices (18 figures). A dollar figure counts only if the owner gives the price of the flush, exchange or coolant service itself, alone or as its own line, on their own vehicle. Totals for bigger repairs, bundles of services, and figures for a flush plus a part were left out. Nine figures are whole-system flushes or coolant services (median $260; six paid or billed, median $230; three quoted, median $299); nine are heater-core flushes (median $450; four paid, median $375; five quoted, median $470).

Documents. 12 manufacturer bulletins and service documents from NHTSA's public files were read; their ids, numbers and links are in the documents file. Owner's manuals, maintenance guides, dealer and chain pages and price sources used in the article are listed with dates in the article's Sources section.

Limits. Complaints over-represent bad outcomes; owners report what they were told and paid as they understood it; "a problem began after a flush" is a sequence the owner reports, not proof that the flush caused it; the set is small for almost twelve years of complaints and cannot give a rate or a price survey; searches of the complaint text miss complaints that describe a flush in unusual words. Coverage and prices in the article are as of November 2026.