1997 Aerostar E-4WD, w/4.0l ohv at 131,000 miles.

Hey guys, I recently changed the heater core in my Aerostar, I drained around a gallon of coolant when I started the process. Once I put everything back together and filled the radiator to burp the system, the coolant kept disappearing. I pour the coolant in and stop near the neck opening, however it drains very slowly (20 mins) and stops just above the inner core tubes/fins. I don't see any leaks coming from the heads or anywhere really. Any suggestions as to why it keeps going out?

 

the engine must have head gasket problems and the cooland is getting burnt in the combustion.

do you get lots of white smoke out the exhaust when engine is cold?

 

No, no smoke what so ever.

 

ok, do you have rear a/c and heater?

if yes, check the rear Heater valve for leaks.

this valve is located outside the van. Behind
the driver's door and rocker panel, under the rear air unit.

 

I checked there, no leaks either. I moved the van onto an incline and filled it up once more, I guess there was just a big pocket of air or something. Thank though!

 

it takes a lot of coolant to fill the 4.0 twin air system and its long hoses to the front and rear evaporators.

 

Okay, the coolant is still disappearing...
i went for a small drive to test it out, it seemed okay. Once I came back, I parked and checked the coolant level once the motor cooled down. I popped the cap and the level was full, I checked again 2 hours later and the radiator was half empty.
I don't see any wetness on the block, the oil looks fine, the trans oil is fine, and with no white smoke is blowing out the back I'm completely lost on what else to look for.

I'm getting some uv dye and checking for any small leaks around the heads and plugs.

 

I once had an external leak on the front corner of the head gasket on the passenger side. The coolant must have been evaporating as it seeped out. There was only one line of sight where it could be seen. I lucked out with some bar's stop leak tablets.

 

I have performed the UV test and can find no leaks at the moment. Maybe the radiator cap is failing?

 

A bad radiator cap will allow coolant into the recovery tank. If you lost half of what is in the radiator, the recovery tank couldn't hold it all and it would go out the overflow onto the ground. But they are cheap and you can try a new one.
If you are sure there aren't any external leaks, you can buy a kit to test for exhaust fumes in the coolant, but as I remember it's a little pricey.
BTW does this thing run rough on first start in the morning and then clear up within a minute or so?

 

A little, it's been running a better since I replaced the EGR feedback sensor a couple days ago. However, when I put the heater core back and hooked everything up, it would run rough then die off once it started to warm up. The only coolant I found was the coolant I spilled onto the recovery tank. Found no coolant with the uv light anywhere else.
If the head was cracked, and allowed exhaust into the cooling system, wouldn't the coolant bounce a lot and have pockets of air coming out like crazy?

 

Bought a block tester kit and performed three tests at operating temp. All three of the tests showed no indication of exhaust gasses in coolant system. To make sure the fluid was working, I stuck the nozzle close to the exhaust and pumped. So far, the block tester and uv dye has shown no results of a cracked head or bad gasket. The cap has to be the issue.

 

my 1997 4.0 does the same thing. I gave up trying to find the cause. It doesn't leak coolant anywhere, outside or inside. l replaced the radiator cap, no change.

the recovery / expansion tank does not have any overflow exit port The engine runs cool but the heater heats like crazy.

Must be the evaporator leaking?
the thermostat always open? I can't figure this one.

 

Are you still losing half a rad's worth each time after sitting? That's a lot of coolant to disappear without going into the engine, oil or ground. I'm wondering if it's just taking a few cycles of operation to fill up the secondary heater's plumbing.

Your problem motivated me to check my coolant, and I did find it down about a quart. The last time I filled it was about a year ago, I have a secondary heater in the back, and I thought I got all the air out of it when I did the fill. A little loss over a long time is expected. All water pumps have a weep hole to allow a small amount of coolant to escape as it leaks past its main seal. This is how it keeps its bearing and seal lubricated. This may be difficult to see, as you have to look from below through the fan belt and any other parts in the way, but try and look for the dye leak around there. Normally that leak is slow enough that you should not see a huge accumulation of wetness, but a light trace of evaporated deposits is normal.

I also had the front right corner of an intake gasket fail, and at first the leak was slow enough that it did not leave a puddle on the floor. I think the area was hidden by the alternator bracket, so it was not easily visible. But once I got into it, I saw a white trail left by the evaporated coolant, and it was obvious where it was coming from.

 

I am anticipating the coolant to be leaking from the intake and freezeplugs. I've burped the system several times over the course of a few days and almost find the radiator to be down a quart after driving to work and back. This only happens after I've finished my shift or from sitting overnight. I've run every test I can think of when looking for a blown head gasket, everything showed no results except for a leaky coolant valve for the heater. No coolant in the oil, no exhaust in the coolant, no coolant in the exhaust, compression is good, plugs show signs of a slightly lean mixture (possible vacuum leak or bad mad/aic), and not a single sign of white smoke from the exhaust. From that, the only possible explanations are a hairpin break in either the head plugs, intake gasket, or somewhere in the coolant lines. I'm going to rebuild the intake section, replace all plugs and line gaskets to see where this annoyance is happening. Honestly, houdini is an amateur compared to my van's magic coolant..