Bubbles in Coolant?

Messages
968
Location
Battle Creek, MI
I have a 2003 Ford F-150 pickup with the 5.4L and about 134k miles and is primarily driven in the winter for daily commuting and can sit around for months at a time. I will tow with it, but since I have owned it starting at 89k I have never overheated the engine. The problem I noticed was an intermittent coolant leak under the front of the engine (haven't been able to pinpoint exactly) and only see the leak during a cooldown period. I have added maybe 1-2 quarts of coolant over the past 6 weeks and last night I checked for the usual signs of a bad head gasket. No water in oil No oil in water No puff of white smoke on startup No rough idle or any other odd symptoms including check engine light The occasional bubble coming up through the coolant overflow tank and increases when the engine is revved (at least when the engine is decelerating since I haven't had a friend help me). I have read a lot people have problems with the coolant overflowing the coolant reservoir and the engine overheats. I don't have anything close to this. My question is what is the right plan of attack to figure out the problem? 1. The first thing I was going to do today is the combustion leak test to check for hydrocarbons 2. Do a compression test 3. Inspect spark plugs while they are out to look for antifreeze or signs of water contamination 4. UOA to test for contamination Is there any other reasons I would see bubbles in the coolant? Maybe a leaking water pump (source of my leak as well)? Bad intake manifold gasket? Thanks for your help.
 
Messages
8,051
Location
Michigan
Maybe a used coolant analysis be able to detect a combustion leak into the cooling system. I don't think a compression test would be able to detect a small coolant leak. If the gasket was seriously blown on one cylinder so that a compression test would definitely show a low reading, you would be pumping water out the radiator anyway. Inspecting the spark plugs is relatively easy, and you may be able to see coolant deposits on the insulators. A blown water pump seal would let coolant drip out of the weep hole, which is always on the bottom of the pump in a place that's hard to see. You could probably see in there with a light and an inspection mirror.
 
Messages
3,181
Location
Ohio
Check the spring clamp on the lower radiator hose at the waterpump. They have a tendency to have a small split in them that is hard to see.
 
Messages
7,485
Location
S California
When't the last time the water pump was replaced? With a chain cam drive the pump is not getting replaced with a cam belt change. If you haven't changed the pump it's probably the original pump and in that case maybe it's time.
 
Messages
2,349
Location
Ontario Canada
The bubbles are not smoky? A friend had a Dodge with a head gasket leak and with the rad cap off it produced smoky bubbles. Remove rad cap when cold of course.
 
Last edited:

SVTCobra

Thread starter
Messages
968
Location
Battle Creek, MI
Originally Posted By: OneEyeJack
When't the last time the water pump was replaced?
Original equipment to the best of my knowledge. The previous owner kept records of all of the service that was done and I don't recall seeing a water pump installation.
Originally Posted By: cjcride
The bubbles are not smoky?
Not at all. And the coolant doesn't get super hot either.
 
Messages
6,174
Location
Illinois
Maybe radiator hot side tank? Almost all Ford I've had develop a leak there over time as the aluminum crimps weaken over time. Usually only leaks when cold though.
 
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