Q: my car leaks coolant but is fine with water. it also recently had a new water pump and thermostat put in why would this happen?

asked by on September 07, 2017

when i bought my car they said they had just replaced the thermostat and water pump. It overheated the same weak and all my coolant leaked out. I put water in it then i had it flushed and refilled with dex cool and now everytime i put coolant in it it leaks but when its only water it holds better and leaks less. Why would this happen?

My car has 140000 miles.
My car has an automatic transmission.

You are probably just seeing "randomness" in the leak rate when you add water versus coolant; both will leak at the same rate. What you want to do, of course, is just simply get the leak pinpointed and repaired. If the cooling system leaks, it obviously will not hold maximum pressure either and the coolant will then potentially boil over and that itself creates overheating (pressure in the sealed cooling system RAISES the boiling point of the coolant). Engine coolant can leak externally through a hose, radiator, water pump, etc. or internally due to a leaking head gasket and sometimes a leaking intake manifold gasket depending on the engine design. External leaks are typically found by simple pressure testing of the cooling system. To find the leak that exists in your case, and get the required repair estimated, please request an engine cooling system leak diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Transmission problems

My first recommendation is to have a certified mechanic verify the symptoms with a thorough transmission inspection that includes a road test. Explain to the technician what you are experiencing so they can look out for these things during the...

Something is draining my battery, both battery and alternator have been checked and are working fine.

Hi. Your diagnosis is spot on! If the alternator and battery are good, something is causing a pretty significant drain on the battery, and this needs to be identified. This problem can be diagnosed by connecting an ammeter to the...

I'm smelling antifreeze an seeing a little steam from under the hood

The engine in your Pontiac Grand Prix is known to corrode out at the corners of the intake and head. The leak starts with a gasket and grows to damage the intake and heads. I suggest removing the intake and...

Related articles

The Best Used Cars to Buy for Occasional Drivers
Not Not everyone relies on their car on a daily basis. Maybe you aren’t the type that deals with a daily commute, and running from here to there constantly. If that’s the case, you may be looking for a car...
How to Buy a Classic Pontiac
Whether you want to buy a classic Pontiac for yourself or as a gift, here are some tips on buying one for a great value.
Understanding the Pontiac Oil-Life Monitor and Service Indicator Lights
Car symbols, or dashboard lights, are a car service reminder. The Pontiac Oil Life Monitor (OLM) indicates when and what service your car needs.