Guide to the 1990-1999 Mitsubishi Eclipse Engine Timing Belt Tensioner
A failing tensioner can destroy your Eclipse's engine; here's how to choose the right replacement.
- A ticking noise from the timing belt area is a critical warning sign of tensioner failure.
- Always replace the hydraulic tensioner as part of a complete timing belt kit, including the belt, pulleys, and water pump.
- For the 4G63 engine, stick to high-quality aftermarket brands like Gates and Dayco, or use a genuine Mitsubishi OEM part.
- Verify your engine type (4G63 vs. 420A) before ordering, as the parts are not interchangeable.
Engine Differences Matter
Before buying any parts, you must know which engine is in your Eclipse. This is the most important step. Most GS, GST (turbo), and GSX (turbo AWD) models have the Mitsubishi 4G63 engine. However, some non-turbo 1995-1999 RS and GS models came with a Chrysler-built 420A engine. These two engines use completely different timing belt components. This guide focuses primarily on the more common 4G63 engine, which has a well-known history regarding its hydraulic tensioner.
Symptoms of a Failing Tensioner
A failing tensioner often gives warning signs before it lets go completely. Ignoring these can lead to one of the most expensive repairs an Eclipse owner can face. Listen for a distinct ticking or rattling noise coming from the timing belt side of the engine, especially at idle. This sound is often the hydraulic tensioner failing and allowing the belt to become loose. You might also hear squealing or grinding if the tensioner pulley bearing is failing. In some cases, a bad tensioner can cause the timing to be slightly off, leading to a rough idle, engine misfires, or sluggish acceleration. If you see any oil leaking from the tensioner itself, it has failed and must be replaced immediately.
🎬 See and hear what a bad hydraulic tensioner sounds like.Do Not Drive
If you suspect your timing belt tensioner is failing, do not drive the car. The risk of the timing belt slipping or breaking is extremely high. On an interference engine like the 4G63, this will cause the pistons to hit the valves, resulting in catastrophic engine failure.
Choosing Your Aftermarket Tensioner: Quality is Critical
For many years, the wisdom in the DSM (Diamond-Star Motors) community was to use only genuine Mitsubishi OEM tensioners. This was due to a history of low-quality aftermarket parts failing prematurely. Today, the situation is better, but quality is still the most important factor. A timing belt job is labor-intensive, so you don't want to do it twice. It's highly recommended to replace the tensioner as part of a complete timing belt kit that includes the belt, idler pulleys, and water pump.
Brand Quality Tiers
- Premium-Tier (Gates, Dayco): Gates is a highly respected brand in the Eclipse community, known for making kits that meet or exceed OEM quality. Dayco is another long-standing OE supplier with a solid reputation. Choosing a complete kit from one of these brands is a reliable and trusted option for the 4G63 engine.
- Mid-Tier / Economy (GMB): GMB is a large manufacturer of aftermarket parts and is often included in timing kits. While they produce a wide range of components, enthusiasts strongly recommend sticking to premium brands or OEM for a part as critical as the hydraulic tensioner on an interference engine.
The "Grenade Pin"
New hydraulic tensioners come with a small pin, often called a "grenade pin," holding the plunger in a compressed state. This pin should only be pulled *after* the entire timing belt and tensioner assembly is fully installed and torqued to specification. Also, when installing, the new tensioner must be compressed very slowly in a vise to avoid blowing the internal seals.
Known Issues, Recalls, and TSBs
No specific recalls or Technical Service Bulletins (TSBs) from Mitsubishi or the NHTSA were found for the hydraulic tensioner itself on the 1990-1999 Eclipse. However, the part's potential for failure is well-documented in owner forums. For the 420A engine, some owners have reported issues with the tensioner bracket alignment causing the timing belt to "walk" off the gears, a problem that sometimes requires shims to correct.
🎬 Watch this guide for installing a 420A mechanical tensioner.Cost of Replacement
The cost of the hydraulic tensioner assembly itself varies by brand. The labor for this job is significant because it is part of a full timing belt service.
| Part/Service | Estimated Cost |
|---|---|
| New Aftermarket Hydraulic Tensioner | $69 - $221 |
| Shop Labor for Timing Belt Service | $600 - $900 |
| Complete Aftermarket Timing Belt Kit (Recommended) | $200 - $350 |
Frequently Asked Questions (FAQ)
Can I reuse my old tensioner?
No. The hydraulic tensioner is a wear item and should always be replaced whenever the timing belt is serviced. The cost of a new tensioner is minor compared to the cost of engine damage if the old one fails.
Is this a good DIY job?
This is an advanced, labor-intensive job not recommended for beginners. The process is complex, requires special tools, and a mistake 🎬 Watch this step-by-step 4G63 timing belt replacement walkthrough. can destroy your engine. Setting the timing correctly and properly pre-loading the tensioner are critical steps that require experience.
How often should the timing belt and tensioner be replaced?
The standard service interval for the 1990-1999 Eclipse 4G63 engine is every 60,000 miles or about 5-6 years, whichever comes first. Age can make the rubber belt brittle, so it's important to replace it even if the car has low mileage.
What's the difference between the 1G and 2G Eclipse tensioners?
The first-generation (1G, 1990-1994) and second-generation (2G, 1995-1999) Eclipses use slightly different parts. For example, early 1G models (up to April 1992) use a different tensioner than later models. It is crucial to order parts that are specific to your vehicle's exact year and engine type.
Helpful Videos
Technical Specifications
OEM Part Numbers: MD164533 MD308587
Hydraulic automatic tensioner. Specific part number depends on production date (pre or post 04/1992 for 1G models) and engine type (4G63 vs 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: