2004 intermittent coolant leak

[Bobwheeler]

Have a difficult to define, intermittent coolant leak in that area. Everything I can see looks good. Road tests are inconclusive. Any hints?
More data: I have changed out the degas (expansion) tank and hose. Found the upper connection broken. Part of the plastic tube came off with the hose. Got it out. Hose reusable. Took it for a 4 mile test drive after filling to between the fill lines. As I stopped in the garage, approx 1 pint (what I added earlier) was discharged on the floor. Drip spot says center of car at about aft end of engine. Next day, after inspection and not adding coolant to approx 1 inch below fill lines, went for same test ride. Stopped in front of garage to avoid mess. Turned it off; no leaks. Put it in the garage; no leaks. No coolant in the car. Visual shows nothing. This is a mystery. Is there a relief valve in the system somewhere? My Tech Service Manual for a 2005 shows a relief valve at the exp tank. I have not bled the high point vent as I never lost more than a cup (8oz) of coolant. Car had been driven 500+ miles with exp tk level down as noted. Filled it to try to do the right thing and now have this mystery. Car will be on a lift 29 Sept. so maybe will see something then. Anybody with a similar situation. Does not make sense to me. Any stories on a bad freeze plug? Thanks.

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[doug7740]

With the engine cold, I would perform a pressure test on the cooling system.

(See instructions below)

doug7740
1955 Thunderbird Blue

 

[74 Harley]

Intermittent coolant leaks can be extremely difficult to find. I have fixed a few of them over the years (not on birds). The ones I dealt with occurred at the point of temperature differential between parts. In other words it would only leak for a few minutes while going from cold to warm. Or during the cooling cycle.
With the car cold place a large piece of cardboard under the car. Start it and let it warm up. A really good flashlight helps. Look for leaks at all of the hose connections and the ends of the manifold. Keep an eye under the car as well. If you don't find anything shut it down after about 20 minutes. Start watching all over again.
Coolant will leave a trail, and may run quite a ways away from the leak before dripping off.
Putting it on ramps may help as well.

 

[Bobwheeler]

With the engine cold, I would perform a pressure test on the cooling system.

(See instructions below)

doug7740
1955 Thunderbird Blue

View attachment 24397

Good idea. Think I can get a test rig at HF. Looks like this is a generic test as it calls for a pressure relief cap which these 2002-2005 cars don't have that I know of. Am I missing something? Rather than removing the cowl vent screen which I just reinstalled after breaking off the snaps to remove it for cabin filter insp. and fixing, can I not use the high point vent tube that slides off the degas bottle and can be pulled out for reasonable access? This engine has no radiator cap per sei, just a filler cap. It doesn't relieve does it? More I think of it, the more I like it. Thanks.

 

[Bobwheeler]

Intermittent coolant leaks can be extremely difficult to find. I have fixed a few of them over the years (not on birds). The ones I dealt with occurred at the point of temperature differential between parts. In other words it would only leak for a few minutes while going from cold to warm. Or during the cooling cycle.
With the car cold place a large piece of cardboard under the car. Start it and let it warm up. A really good flashlight helps. Look for leaks at all of the hose connections and the ends of the manifold. Keep an eye under the car as well. If you don't find anything shut it down after about 20 minutes. Start watching all over again.
Coolant will leave a trail, and may run quite a ways away from the leak before dripping off.
Putting it on ramps may help as well.

Also a good idea. Getting the car off the ground has a few problems. Do you know if a floor jack can be placed under the car at a safe spot that won't break anything? Would simplify getting jack stands in place. Thanks for your input. I shall prevail!

 

[Bobwheeler]

With the engine cold, I would perform a pressure test on the cooling system.

(See instructions below)

doug7740
1955 Thunderbird Blue

View attachment 24397

You know, the service manual on a thumb drive from ebay for a 2005 shows a relief valve right by the degas tank. I know it's a dumb question but, is there supposed to be one? I don't have one. The text does not talk about it. It makes sense to have one. More mysteries. The tstat housing, pipe and hoses are all recent (a year ago). Cap is not. What am I up against here?

 

[doug7740]

The test procedure that I attached was not generic it came straight from the service manual. Item #13 in the illustration and picture below is the relief valve next to the degas bottle. The relief valve is used to bleed air from the cooling system. The relief valve is part of the hose that is attached to the coolant pipe that runs along the firewall. If it is missing or not located next to your degas bottle, that might the cause of your coolant leak.

doug7740
1955 Thunderbird Blue

 

[Bobwheeler]

Have a difficult to define, intermittent coolant leak in that area. Everything I can see looks good. Road tests are inconclusive. Any hints?
More data: I have changed out the degas (expansion) tank and hose. Found the upper connection broken. Part of the plastic tube came off with the hose. Got it out. Hose reusable. Took it for a 4 mile test drive after filling to between the fill lines. As I stopped in the garage, approx 1 pint (what I added earlier) was discharged on the floor. Drip spot says center of car at about aft end of engine. Next day, after inspection and not adding coolant to approx 1 inch below fill lines, went for same test ride. Stopped in front of garage to avoid mess. Turned it off; no leaks. Put it in the garage; no leaks. No coolant in the car. Visual shows nothing. This is a mystery. Is there a relief valve in the system somewhere? My Tech Service Manual for a 2005 shows a relief valve at the exp tank. I have not bled the high point vent as I never lost more than a cup (8oz) of coolant. Car had been driven 500+ miles with exp tk level down as noted. Filled it to try to do the right thing and now have this mystery. Car will be on a lift 29 Sept. so maybe will see something then. Anybody with a similar situation. Does not make sense to me. Any stories on a bad freeze plug? Thanks.

So here we are a month later and no more leaks on the floor. The coolant pressure test done by the shop on 29 Sep. showed a leak at the tstat housing but it does not leak during normal running. I have discussed on another post. For now I am taking no action. Seems like the new exp. tank fixed the leak. Car runs very well. End of story.

 

[Mark James]

So here we are a month later and no more leaks on the floor. The coolant pressure test done by the shop on 29 Sep. showed a leak at the tstat housing but it does not leak during normal running. I have discussed on another post. For now I am taking no action. Seems like the new exp. tank fixed the leak. Car runs very well. End of story.

My philosophy is if it’s not the head gasket everything else can be tracked down over time and with some patience.

 

[The Flash]

The last leak I had was from the radiator, where the top hose connects. The plastic was cracked. had to put in a new radiator.
My other leaks have been from;
the coolant tank, replaced it three times now.
The O rings at the thermostat, had that happen two times.

 

[Terry Humphrey]

Have a difficult to define, intermittent coolant leak in that area. Everything I can see looks good. Road tests are inconclusive. Any hints?
More data: I have changed out the degas (expansion) tank and hose. Found the upper connection broken. Part of the plastic tube came off with the hose. Got it out. Hose reusable. Took it for a 4 mile test drive after filling to between the fill lines. As I stopped in the garage, approx 1 pint (what I added earlier) was discharged on the floor. Drip spot says center of car at about aft end of engine. Next day, after inspection and not adding coolant to approx 1 inch below fill lines, went for same test ride. Stopped in front of garage to avoid mess. Turned it off; no leaks. Put it in the garage; no leaks. No coolant in the car. Visual shows nothing. This is a mystery. Is there a relief valve in the system somewhere? My Tech Service Manual for a 2005 shows a relief valve at the exp tank. I have not bled the high point vent as I never lost more than a cup (8oz) of coolant. Car had been driven 500+ miles with exp tk level down as noted. Filled it to try to do the right thing and now have this mystery. Car will be on a lift 29 Sept. so maybe will see something then. Anybody with a similar situation. Does not make sense to me. Any stories on a bad freeze plug? Thanks.

Had a similar problem with my 2005 turned out to be the plastic coolant filler cap. It would only leak after getting very warm.