Over the summer, a radiator leak lead to my engine overheating. I've since had both the radiator and motor replaced.

A few months later, I noticed my coolant levels were abnormally low, so I took the car in for a leakdown test. They said they couldn't find anything.

I checked my levels not long after and it seems like I've lost more coolant. Where should I go from here?

 

Pressure test is typically for coolant leaks, not a leakdown test.

Do you keep topping it up, and it keeps getting low?

 

Only places I can think of losing coolant is the radiator, or the water pump. If not that, then it's being burned by the engine. Pressure testing the radiator is the cheapest easiest way to find a coolant leak. If it ain't coming out of the engine, radiator, or hoses, it's coming out the tailpipe. Then again if there are air pockets in the cooling system as the system slowly burps itself, it will lower your coolant level.

 

This has the sound of head gasket problems. Better get the coolant system pressure tested.

 

Oil analysis will detect both antifreeze and water. Shouldn't be any.

Blackstone will send you the kit free. You just pay for the test when you mail it in. Results take about a week.

-- Chuck

 

heater core? Does inside of car have a sweet smell?

 

external leaks can almost always be smelled, the sweet smell as the engine bay heats up can't be mistaken.

Some common sources of leaks are the smaller coolant hose lines that run under the throttle body, they are used to heat the throttle body and also run to the idle air control valve on the intake manifold.. Run your hand under there and see if it is damp. If you have an aftermarket phenolic intake manifold gasket, check to see if it is leaking, they are famous for leaking when people install them. Water pumps will weep coolant, you would normally see a wet spot on the ground when parked. Common sources to check. Take a bright flashlight and check all parts of the engine bay and under the vehicle, look for coolant dripping.

 

I will just add to check the drain valves too. It has taken a few months for me but just last week I finally discovered that is the source of a slow intermittent leak in my 1999 Jeep. Who knows?

 

A problem I had on my Accord recently, the pressure cap seal became pitted over time and caused the overflow tank to literally overflow; all over the engine bay.

It seems if the cap seal is damaged the system won't hold pressure, instead redirecting all the hot expanded liquid to the overflow tank which is not sealed by design.

I read this can also lead to water evaporating out of the coolant mixture, but I'm not sure how true that is but it could cause low coolant levels.

Not sure if this is your issue, but it is something a cooling system pressure test won't find.

I could only determine it by opening the cap when the engine was hot and experiencing no pressure release. Obviously be careful and use gloves and a towel and if you try this...

 

I'm betting on no leak, but rather air pockets, as someone else also mentioned.

The original radiator leaked, engine overheated. They were both replaced, but its difficult to purge all the air out, especially if engine (and radiator) were basically dry.

So now coolant level keeps coming up low, but its not coolant leaking out, its air bleeding out. The assumption is its leaking because that is what happened before.

This is a dangerous situation, and can lead to a repeat of overheated and destroyed motor.

Test this out. Omce car is warmed up, crank heater. If its not very difficult to hold your fingers up to the vent for more than several seconds, you got air.

DO NOT drive this car until you can rule out air in coolant. Air pockets are a ticking time bomb. Motor will overheat past damage point with little warning.