Rick's Free Auto Repair Advice

Do you have a bad water pump?

How to diagnose a bad water pump

If you have a bad water pump some of the first things you’ll notice are:

1)      Engine temp rises at stops
2)      Low or no heat at stops
3)      Signs of coolant leaks under engine
4)      Rattling noise under hood

Start by checking coolant level

Low coolant level can cause circulation problems

coolant level

Check coolant level in recervoir

that are similar to a failing water pump. Check the coolant reservoir and the radiator for proper coolant levels first.

Next, determine the state of your cooling system

Corrosion is the enemy of every cooling system. You can perform a coolant test to determine the coolant’s cold protection properties, but those testers will not tell you the coolant’s state of anti-corrosion additives. To do that you must perform an electrolysis voltage test with a multi-meter.

You can also test the pH of the coolant using test strips

coolant test strip

Coolant test strips measure water/coolant ratio, pH and acid reserve.

test antifreeze with multimeter

Corrosion can destroy a water pump

Pop the radiator cap and look for signs of

View of clogged radiator from the filler neck

This is what neglect looks like

corrosion inside the radiator. If the system has been neglected and corrosion has begun, chances are high that the water pump has also been damaged.

Check for noise from bad water pump

A worn water pump bearing will make a growling noise. In the early stages of wear, that noise can be hard to detect without an automotive stethoscope. But by touching the stethoscope probed the water pump bearing area, you can diagnose a bearing issue in an instant.

water pump cutaway

Check for coolant flow

Simply remove the radiator cap and start the engine. Once the thermostat opens, you should see coolant movement in the radiator. That confirms that the water pump is moving coolant

Check for bad water pump leaks

Every water pump has an input shaft seal that allows the pulley input shaft to turn the impeller yet prevent coolant from escaping. If you neglect cooling system maintenance and corrosion builds, the corrosion wears out the seals and the water pump leaks through the seal area.

Water pump replacement tips

If your diagnosis leads you to believe you have a bad water pump and you’re going to replace it yourself, follow these installation tips:

1) ALWAYS flush the entire cooling system before you remove the old pump. Do be stupid here. It makes no sense to swap a new pump into a dirty corroded cooling system. Flush it first. Then remove the old pump and swap in the new one.

2) NEVER rotate the shaft of a new water pump when the pump is dry. You can damage the seals even before you install it by rotating the shaft against dry seals. The seals require coolant as a lubricant.

3) Watch that sealer! Whoa dude, did the shop manual really call for RTV sealant? Adding an RTV sealer may sound benign enough, but using RTV sealer when you don’t need it can cause all kinds of problems down the road. Follow these rules about gasket sealing:

• If the water pump comes with a paper gasket it doesn’t need sealant Period. The end

• If the water pump comes with a silicone gasket, it doesn’t need sealant unless specified in the instructions.

• If the water pump doesn’t come with a gasket or no gasket is listed for your application, THEN you should use and RTV gasket maker (like the RIGHT STUFF by Permatex).

• ALWAYS, always always use a torque wrench when tightening bolts. Water pump housings are made from a soft magnesium material that can warp if not tightened in the proper pattern and torque. Following the tightening sequence shown in the shop manual and use a torque wrench.

• Bleed air out of the system using a vacuum bleeder. Air in the cooling system can quickly destroy the new pump through cavitation.

• Use the recommended coolant when refilling. There is no such thing as “all makes, all models” coolant. Coolant, even dealer coolant is cheap compared to the cost of early radiator, heater core and water pump failure. Use the right coolant.

©, 2019 Rick Muscoplat

Posted on by Rick Muscoplat



Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN