Engine Water Pump Replacement for the 1995-1999 Mitsubishi Eclipse
Understanding the critical differences in water pump service for 420a and 4G63T engines is key to a successful repair.
- You MUST identify your engine: 420a (non-turbo) and 4G63T (turbo) use different pump designs and replacement procedures.
- For 4G63T turbo models, ALWAYS replace the timing belt, tensioners, and pulleys with the water pump.
- Aisin is the OEM manufacturer and the most recommended brand; Gates and GMB are trusted aftermarket alternatives.
- A minor stain from the pump's weep hole can be normal, but a steady drip means immediate replacement is needed.
Is it for a 420a or 4G63T Engine? Know This First.
Before you buy a water pump for your 1995-1999 Eclipse, you must know which engine you have. The replacement job is completely different for each.
- 4G63T Engine (Turbo GST, GSX models): The water pump is located behind the timing belt covers and is driven by the timing belt. Replacing this water pump is a major service job. It requires removing the timing belt, so the water pump, timing belt, and all related tensioners should be replaced at the same time. 🎬 Watch: Full 4G63T timing belt and water pump replacement walkthrough
- 420a Engine (Non-Turbo RS, GS models): The water pump is driven by the external serpentine belt. This makes it much easier to access and replace. While still a significant repair, it does not require a full timing belt service. 🎬 See how to remove the water pump on a 420a engine
Symptoms of a Failing Water Pump
A bad water pump will give you clear warning signs. Ignoring them can lead to severe engine damage from overheating.
- Coolant Leaks: This is the most common symptom. You may see puddles of green, orange, or pink fluid under the front-center of your car. Sometimes, a slow leak won't hit the ground but will leave a white or colored crusty residue on the engine near the pump.
- Engine Overheating: If the pump fails, it can't move coolant. Your temperature gauge will climb into the red zone, and you might see steam coming from under the hood. If this happens, pull over and shut off the engine immediately.
- Whining or Grinding Noises: A high-pitched whine or a rough grinding sound from the front of the engine that changes with engine speed often points to a bad bearing 🎬 Watch: How to identify common bad water pump symptoms inside the water pump.
A Note on Leaks from Mitsubishi
Mitsubishi issued a technical service bulletin (TSB-19-14-001) for all its models. It states that a small amount of coolant stain or residue near the pump's "weep hole" can be normal. This happens as tiny amounts of steam pass through the seals. A small stain is not always a sign of failure, but a steady drip or puddle means the pump needs to be replaced.
Choosing the Right Aftermarket Water Pump
For a critical part like the water pump, especially on the 4G63T engine, quality matters. The original manufacturer for Mitsubishi was Aisin, which is available as an aftermarket brand and is considered the best choice by enthusiasts.
- Top Tier (OEM Quality): Aisin is the original supplier and a direct replacement. For the 4G63T, pairing an Aisin pump with a Gates timing kit is a popular, reliable combination.
- Trusted Aftermarket: Gates and GMB are well-regarded brands in the DSM (Eclipse, Talon, Laser) community. They offer a good balance of quality and price. Many owners use them with success, though some recommend using a higher-quality gasket, like one from Fel-Pro or OEM, instead of the one included in the box.
- Standard Aftermarket: Brands like ACDelco and US Motor Works offer replacements that meet factory specifications. They are functional choices, though they don't have the same strong reputation in the Eclipse community as Aisin, Gates, or GMB.
| Part/Service | 420a (Non-Turbo) | 4G63T (Turbo) | Notes |
|---|---|---|---|
| New Aftermarket Water Pump | $43 - $76 | Price for the pump itself. | |
| New OEM Water Pump | $150 - $200+ | Aisin is the OEM manufacturer. | |
| Shop Labor | $200 - $400 | $470 - $700+ | 4G63T labor is much higher because it includes a full timing belt service. |
| Total Estimated Cost | $243 - $476 | $620 - $900+ | Total cost can vary significantly based on location and other parts replaced. |
Common Ordering Mistake
Do not buy a water pump based on your car's trim level alone. Always verify if you have the 420a (non-turbo) or 4G63T (turbo) engine. The parts are not interchangeable, and the required labor is vastly different.
Frequently Asked Questions
Do I have to replace my timing belt with the water pump?
If you have the 4G63T (turbo) engine, the answer is YES. The water pump is driven by the timing belt, and you have to do 95% of the labor for a timing belt job just to reach the pump. It is standard practice to replace the timing belt, water pump, and all tensioners and pulleys at the same time. For the 420a (non-turbo) engine, it is not required, as the pump is driven by the accessory belt.
Are there any recalls for the water pump?
No. There have been no recalls issued by the NHTSA for the engine water pump on the 1995-1999 Mitsubishi Eclipse.
Can I just replace the gasket if it's leaking?
It is not recommended. The leak is usually a sign that the internal seal on the pump's bearing is failing. Replacing only the outer gasket will not fix the root cause, and the pump will likely continue to leak from its weep hole. Given the labor involved, especially on a 4G63T, you should always replace the entire pump assembly.
What is a water pump "weep hole"?
The weep hole is a small opening on the water pump housing. It is designed to let small amounts of coolant escape if the internal shaft seal begins to fail. A few drips or a light stain can be a normal sign of age, but a constant drip means the seal has failed and the pump must be replaced soon.
Helpful Videos
Technical Specifications
OEM Part Numbers: MD972050
OEM Part Number MD972050 applies to the Aisin pump for the 4G63T engine. The 420a engine uses a different part. Drive type is the key specification: timing belt-driven for 4G63T, serpentine belt-driven for 420a.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mitsubishi Eclipse: