Common Problems on the 1994-04 Chevy S10

Mechanic showing Chevy S10 Problems

1994-2004 Chevy S10 common problems include intermittent starting, an S10 that won’t start after sitting, an S10 that turns over but won’t start, and other issues like fuel pump problems. Find out their symptoms, causes and fixes as we explore the top problems on the 2nd generation of Chevy S10 trucks, also known as the Chevy S-10 or Chevy S-series.

Repair some of these common problems and more on the Chevy S10 with 1A Auto’s videos

Top Issues on the 2nd Generation Chevy S-10 (1994-2004)

1. Faulty Heater Core

Symptoms of a Faulty Heater Core

  • Cold air blows from the heater vents when the heat is on
  • Windshield fogs up while driving, sweet smell in the cabin, and/or coolant leaking on the passenger side floor

Causes of a Faulty Heater Core

  • If cold air blows from the vents when the heat is on, the heater core is clogged from old coolant or sediment. This can happen from not performing a regular coolant flush.
  • If coolant leaks on the passenger side floor, if there is a sweet smell in the cabin, or if the windshield fogs up when driving, the heater core is leaking.

How to Fix a Faulty Heater Core

  • If the heater core is clogged and not damaged, try flushing the heater core to extend its life. If the heater core is damaged, replace it. Replacing the heater core includes removing the dash, steering column, and heater box to access the heater core.
  • If the heater core is leaking, replace the heater core

2. Bad Intake Manifold Gaskets

Symptoms of Bad Intake Manifold Gaskets

  • High level of engine oil with a milky color
  • Low coolant
  • Coolant leak near or behind the water pump
  • Cross-contamination of engine oil and coolant in the coolant reservoir

Causes of Bad Intake Manifold Gaskets

On the 94-04 Chevy S10, coolant travels through the intake gasket, so it can look like the water pump is leaking, but on this pickup it’s usually the intake gaskets leaking

How to Fix Bad Intake Manifold Gaskets

  • An intake manifold gasket replacement on the 2nd gen S10 is a big, detailed job. It requires the removal of the upper engine parts like the fuel lines and the A/C compressor

3. Distributor Problems

Marked spark plug wires and corresponding cylinder on the distributor cap
Marked spark plug wires and their corresponding cylinder engraved on the distributor cap

Symptoms of Chevy S10 Distributor Problems

  • Engine misfires
  • Engine turns over but won’t start
  • Check engine light for misfire code P0300-P0306

Causes of Distributor Problems

Common problems with the distributor on the Chevy S10 are from a bad distributor cap and rotor, but sometimes it’s from worn internal parts

How to Fix Distributor Problems

The distributor is located near the firewall. To prevent distributor problems, routinely change the distributor cap and rotor. Check the owner’s manual for recommended intervals, which is usually around 60-100,000 miles.

  • Remove the screws on each side of the distributor cap
  • Replace the distributor cap or rotor if it has corrosion or carbon deposits
  • If replacing the distributor, for an easier install consider marking the cylinder number the spark plug wires lead to, which is written on the distributor cap, with a marker
Fix common Chevy S10 problems yourself with quality auto parts at 1aauto.com

4. Front Wheel Bearings

Symptoms of Bad Front Wheel Bearings on the 4th Gen Chevy S10

Growling sound at the front wheels at certain speeds, usually over 30 mph

How to Fix a Bad Front Wheel Bearing

  1. Jack up the front of the vehicle up and spin the wheel, listening for a growl or whirring sound
  2. Grab the tire from the 12 and 6 o’clock positions. If there is excessive “play” or looseness in the bearing, the S-10 could have a bad wheel bearing
  3. Purchase quality wheel bearings at 1aauto.com and replace them yourself. To replace the wheel bearing yourself, check out the steps in this video.

5. Fuel Pump Problems

Symptoms of Fuel Pump Problems

  • Engine cranks but won’t start
  • Intermittent starting
  • Extended crank eventually starts the engine

Causes of a Fuel Pump Problems

A bad valve inside the fuel pump sends fuel back into the tank, leaving no fuel or fuel pressure in the fuel lines. Cranking the engine without readily available fuel will cause extended cranking. Turning the key on and off and on and starting the vehicle will prime the system, which is necessary if the S10 won’t start after sitting for a few hours or more.

How to Fix Fuel Pump Problems on the Chevy S10

  • If the S10 won’t start after sitting for a few hours or more, try turning the key to the ON position, and then turn the key to the OFF position. Turn the key back to the ON position, and crank the engine.
  • The fuel pump is located in the gas tank. If the fuel pump is defective, it needs to be replaced. Replacement requires lowering the gas tank. This can be done from underneath the vehicle by supporting the tank and removing the straps, or by removing the bed to the side to access the fuel pump. One method might be easier than the other depending on how old and rusted the truck is.
  • To prolong the life of a fuel pump, keep more than 1/4 of gas in the tank to keep the fuel pump cool and running efficiently.
  • Change the fuel filter about every 30,000 miles or less to keep a consistent flow of fuel and to reduce strain on the fuel pump

6. Defective Vacuum Switch

Vacuum switch on top of the transfer case on a Chevy S10
Vacuum switch on top of the transfer case

Symptoms of a Defective Vacuum Switch

  • Vacuum switch is leaking transfer case fluid
  • Excessive fuel mileage or wearing of front end components, like the HVAC controls and vent doors not working
  • Transfer case fluid inside the HVAC system

Causes of a Defective Vacuum Switch

When four-wheel drive (4WD) is activated, an encoder motor electronically shifts the transfer case to 4WD and presses a vacuum switch at the top of the transfer case that sends vacuum to the front differential. Sometimes when shifting from 4WD to two-wheel drive (2WD), the front differential is still engaged from the switch being stuck in the open position and continually sending vacuum to the front differential.

If the switch is stuck open, transfer case fluid can travel up the vacuum line that leads from the vacuum switch to the engine. This can cause transfer case fluid to leak out of the switch. It can also cause transfer case fluid to travel up to the engine from the vacuum line, and this line is connected to the HVAC system. Since the HVAC system is vacuum actuated, the transfer case fluid can sneak inside the HVAC system and deteriorate the rubber parts of the actuator, making them defective. This will also cause the vent doors to not open, close, and move as directed, and it can break the HVAC control unit if fluid gets inside.

How to Fix a Defective Vacuum Switch

Functional vacuum switch on a Chevy S10
Properly looking and functional vacuum switch
  • To prevent this problem, change the vacuum switch regularlyevery 3-4 years, depending on how often you drive
  • To replace the vacuum switch, remove it with a 7/8″ wrench. If the ball at the bottom of the sensor is stuck flush with the sensor, the sensor is faulty. The ball should be protruding from the sensor and able to be pressed in and out.
Chevy S10 junction connector behind the glove box
Junction connector behind the glove box

To inspect the HVAC system for transfer case fluid

  1. Remove the Glove Box

    Lower the glove box or remove it to access parts of the HVAC system

  2. Remove the Junction Connector

    Disconnect the electrical connector

  3. Inspect the Junction Connector

    Inspect the electrical connector for transfer case fluid or oil-based fluid. There should be no fluid on the connector. If there is, you’ll need to replace the switch and clean out the lines, which can be a difficult job.

Replace Chevrolet S-10 Parts Yourself with 1A Auto’s How-to Videos

Find out how to repair common problems like the ones mentioned in this article and more on your Chevy S10 with 1A Auto’s how-to video. Find install videos for many years, makes, and models in 1A Auto’s video library.

Shop 2nd Gen 94-04 Chevrolet S-10 Parts Mentioned in This Article

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Summary
Chevy S10 Common Problems | 2nd Gen 1994-2004
Article Name
Chevy S10 Common Problems | 2nd Gen 1994-2004
Description
Learn the symptoms, causes and fixes as we explore the top problems on the 2nd generation of Chevy S10 trucks, also known as the Chevy S-10 or Chevy S-series.
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Publisher Name
1A Auto
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