MX-13 coolant-loss guide: level history, leak evidence and exact application.

PACCAR MX-13 Coolant Loss: Checks Before an EGR Cooler

by Advanced Truck Parts on Oct 31, 2026 Categories: Parts & Maintenance

Back to the ATP Garage guide libraryPACCAR / MX-13 / Coolant-loss diagnosis

Quick answer: Confirm a repeatable coolant-level change, record any external leak evidence and ask for the engine-matched findings that identify the leak path before ordering an EGR cooler. PACCAR's historical examples distinguish coolant-level or pump-seepage misdiagnosis from a true leak, and separately direct technicians to diagnose coolant loss when coolant is found in an EGR venturi. Neither finding alone proves that the cooler needs replacement. [1] [2]

Application: MX-13 coolant-loss planning with separate MY2013–2014 chassis and narrowly scoped MY2019–2020 diagnostic examples. E276 includes turbo, software, rating and fault conditions. Current instructions for the actual engine and chassis control testing. No universal cooler-test pressure or replacement diagnosis is supplied.

Keep hot-system and warning instructions first. PACCAR warns against opening a hot coolant fill cap. Follow the truck's stop-engine or overheating instructions and arrange service as required; do not open a hot, pressurized system to investigate a level change. [3]

Is the MX-13 actually losing coolant, or are the readings inconsistent?

Keep a record of the level, inspection conditions, added amounts, dates and mileage. Include whether the cooling system was recently drained, filled or repaired. Tell the shop whether the concern is a warning only, a repeatedly falling level, a visible leak or another observed change.

TIB 42-052, released April 16, 2014, covers MY2013–2014 MX-13 chassis. Its T680/T880 level-check discussion explains how parking on an incline can mislead a reading from that surge-tank design and lead to overfilling. It directs the applicable purge procedure after draining. Keep those chassis conditions with the example rather than copying its tank guidance to every truck. [1]

For the installed chassis, use its current level-check and refill instructions. Compare readings taken under consistent prescribed conditions. A top-up made after a different parking position or recent refill should not automatically be logged as proof of an internal engine leak.

Does residue at the coolant-pump weep hole prove the pump has failed?

The same April 2014 bulletin distinguishes a dry red coolant spot and lesser seepage classifications from continual dripping that calls for replacement in its procedure. It was issued in response to unnecessary pump replacements and misdiagnosed low-coolant conditions. A mark at the pump is a reason to classify the evidence, not a diagnosis for every MX-13. [1]

Ask the technician to identify fresh leakage, its location and severity, and the applicable service criteria. Safe overview and close-up photos can help preserve what was observed before cleaning or repair. PACCAR's cited operator manual also calls for checking cooling hoses and clamps for damage. [3]

Does coolant found in the EGR venturi identify a leaking EGR cooler?

It is evidence that needs further diagnosis. E276, released February 24, 2021, includes a troubleshooting attachment dated February 22, 2021. Its MX-13 application is MY2019–2020, HE400 turbo, RC03/04 software and rating at or below 456 hp, with the bulletin's P1710 circumstances. Those conditions matter; it is not a generic procedure for every EGR or coolant complaint. [2]

In that specific process, the venturi and differential-pressure passages are inspected for blockage, excessive soot and coolant. When coolant is present, the instruction is to diagnose and correct the coolant-loss issue. It does not declare the EGR cooler failed merely from that observation. Have the shop document the actual finding and the further evidence identifying its source. [2]

If an EGR fault is also present, keep its original report with the coolant history. The MX-13 EGR fault guide covers separate sensor and contamination examples; they should not be combined into a diagnosis of your engine.

What should be established before replacing the MX-13 EGR cooler?

Ask what evidence isolates the leak to the proposed component. The service report should name the complete applicable test, its conditions and result, rather than supply only “cooler suspected.” Have the technician use current engine-matched instructions for pressure, duration, isolation and acceptance criteria; this article supplies none of those limits.

Observed concern	Keep with the record	Before a parts decision
Level change or warning	Prescribed check conditions, top-up amounts and recent refill history.	Confirm the actual recurring complaint.
Residue or visible leakage	Location, fresh/wet evidence, severity and photos.	Identify the source using the applicable criteria.
Coolant found in the EGR path	Exact location, conditions and associated diagnostic report.	Document the test that identifies the leak path.
Concern returns after repair	Before/after level record, fitted parts and verification results.	Compare the original complaint with the repeat event.

The general EGR-cooler evidence guide offers more questions for the quote. Its Detroit examples are not MX-13 pressure-test specifications. Keep a confirmed leak repair, any associated service and unresolved findings separate in the estimate.

What identifies the correct MX-13 cooling-system replacement?

Provide the VIN, full engine serial, confirmed emissions/model information, installed component markings, safe photographs and diagnostic report. Include previous engine, cooler or cooling-system replacement history. Have the quote name the exact assembly and required installation items.

PACCAR's MX Access description lists RMI service instructions and parts information. Have the supplier and installer reconcile the current application and repair scope before ordering, then retain the completed leak check and level-verification record. [4]

Send the diagnosed application to ATP

Use the part-fitment request with the identifiers and findings. For a separate starting complaint, see the MX-13 fuel and no-start guide. Exact fitment and availability require confirmation.

Common MX-13 coolant-loss questions

Does coolant loss with no puddle prove an EGR-cooler leak?

No. Request findings that identify the actual leak path.

Does every dry mark at the water pump justify replacement?

No. Classify the finding using the criteria for the installed application.

Does coolant in the venturi identify the failed part?

It calls for coolant-loss diagnosis; the source still needs to be established.

Can I use a cooler-test pressure from a different engine?

Use the complete current test matched to this engine and component.

What should be checked after the repair?

Retain the completed verification and compare the level under the prescribed conditions with the original complaint.

Technical sources and application notes

These primary manufacturer documents support the stated examples. Dated bulletins explain diagnostic distinctions; the current service information for your engine controls the repair. ATP prepared this editorial guide; no independent technician review is claimed.