NHC MOTORS · SERVICE RECORD

Kia K8 coolant and brake fluid service, plus Road Force measurement

This 2021 Kia K8 received a cooling-system cleaning and coolant change, BG PF7 pulsed brake-fluid exchange and loaded wheel/tire measurement. On the machine’s placement screen, assembly number 4 had an RFV of 11.5 kg and was marked red.

BG Cooling System Cleaner used during cooling-system cleaning.

2021 Kia K8

We changed the coolant and brake fluid on this 2021 Kia K8 and measured its wheel/tire assemblies on a Road Force machine. The placement screen marked machine number 4 red at 11.5 kg RFV, higher than the other three.

Engine-side work also included HHO carbon cleaning and a fuel additive; the new brake fluid was BG Super DOT 5.1. We checked the battery for discharge. For the tires, we measured mass balance, rim shape and the variation in force under load as separate things.

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Cleaning the cooling system and changing coolant

We connected service hoses in the engine bay and cleaned the cooling circuit with BG Cooling System Cleaner. We then changed the coolant and added BG Universal Super Cool. The cleaning and change addressed used coolant and contamination in the circuit.

Coolant carries engine heat to the radiator and helps protect the circuit internally. After service, check whether the level remains stable with the engine cold.

During the same visit we also performed HHO carbon cleaning, added BG 44K to the gasoline fuel system and checked for battery discharge.

Service hoses connected in the engine bay for the coolant work.

BG Universal Super Cool added with the coolant.

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Exchanging brake fluid with the BG PF7 pulsed system

We changed the brake fluid using the BG PF7 pulsed method and filled the system with BG Super DOT 5.1. After working at the reservoir, a hose was attached at each wheel outlet to move the old fluid through the brake circuit. Pulsing the flow helps move fluid that can remain in less direct parts of the circuit.

Brake fluid transmits pedal force to the brakes and absorbs moisture over time. Its condition and time in service matter even on a low-mileage vehicle.

BG PF7 pulsed brake-fluid exchange machine.

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Separating mass balance, rim runout and RFV

We measured the wheel/tire assemblies under load. One screen showed current assembly RFV of 9.5 kg and rim runout of 0.05 mm. A separate screen showed current RFV of 11.0 kg and a predicted match value of 10.0 kg. These are separate readings, not a before-and-after pair.

Balance correction in grams concerns mass distribution. Rim runout in millimeters concerns how true the wheel runs. RFV in kilograms represents variation in the tire’s rolling force under load. Correcting mass imbalance alone may leave vibration if a rim is bent or a tire does not deflect evenly.

The predicted 10.0 kg is the machine’s estimate for changing the tire’s position on the rim. Only a fresh measurement after doing that could establish the actual result.

Road Force screen showing current RFV 9.5 kg and rim runout 0.05 mm.

A separate screen showing current RFV 11.0 kg and predicted match 10.0 kg; the latter is an estimate.

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Assembly number 4 showed 11.5 kg RFV in red

The placement screen showed RFV of 6.0 kg for machine number 1, 6.5 kg for 2, 5.0 kg for 3 and 11.5 kg for 4. Only number 4 was red. These are machine identifiers, not front/rear or left/right positions on the car.

The same screen showed a minimum-pull arrangement of 10 N. This is the machine’s calculated placement value, with different units and meaning from RFV in kilograms. It is not an on-road measurement of actual vehicle pull.

Number 4 measured higher than the other three assemblies. If you feel a vibration, tell us the speed and whether it reaches the steering wheel or seat; that helps decide whether to remeasure or consider tire matching.

RFV and calculated minimum-pull placement for machine numbers 1–4. Number 4, at 11.5 kg, is marked red.

K8 Road Force: RFV by machine ID

Only number 4, at 11.5 kg, was marked red on the machine screen.

Machine ID 1

6.0 kg

Machine ID 2

6.5 kg

Machine ID 3

5.0 kg

Machine ID 4

11.5 kg

IDs 1–4 are machine identifiers, not positions on the vehicle. The chart shows the four RFV readings on one measurement screen.

Frequently asked questions

Can a tire still vibrate after its balance is corrected?

Yes. Balance corrects mass distribution; RFV measures force variation while the tire rolls under load. Number 4 on this K8 was marked red at 11.5 kg. Whether the vehicle actually vibrates must be judged with the driving symptoms.

Is the predicted 10.0 kg a confirmed after-work result?

No. It is the machine’s estimate if the tire is repositioned on the rim. The actual value requires remeasurement of that assembly after repositioning.

Must coolant and brake fluid be changed together?

No. They belong to separate systems with their own service timing. Both were changed on this K8 visit, but their next service dates should be considered separately.

K8 coolant and brake fluid service with a tire-vibration check

Tell us when the coolant and brake fluid were last changed. If you feel vibration, also note the speed and whether it reaches the steering wheel or seat. We can check mass balance, rim shape and loaded RFV before advising on matching or tire replacement. Contact us to book.

We explain the work and estimate before proceeding with your consent.

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031-258-1617 · NHC Motors, Suwon · By appointment

Published 2026-09-26