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papasmif · 08-10-2015, 07:08 PM

Hi All,
I recently bought a 2000 Pace Arrow w/Ford V10 engine. It has 63K miles. It pushes Antifreeze out of the coolant container cap after about 20 minutes or so of driving. It usually happens when going up a long hill or when I tow my car. One local truck garage said it was the pressure cap and charged me just under $300 to put a new one on (Ford OEM). They also did a pressure check and didn't find anything. It wasn't the pressure cap as it still does the same thing. It looses about 2 quarts of fluid on a trip. They didn't want to work on it and I can't find anyone including the local Ford dealer who will work on it. They all say they don't work on Class A RVs.
Last week I went about 60 miles away and it blew out the coolant up a long hill on the interstate. I had the air conditioning on then. On the way home, I took the lower flat land route around the mountain and along the river and kept it down under 50 MPH. I did not run the air either. It seemed hot when I got back, but it did not loose antifreeze.
I would think that it is over heating but the Temp gauge stays fixed (just shy of half way). I have no garages in the area that even want to look at it and certainly none with any experience.
Does anyone have any idea or personal experience as to why it would do this ?

thanks for any help, Bob

Tom N · 08-10-2015, 07:11 PM

Possible stuck thermostat.

Skip426 · 08-10-2015, 07:23 PM

There is a chemical test for , combustion chamber gasses in the coolant ; to check for head gasket ( cracked cyl head issues) did the shop do that test?

Have you checked the rad fan's thermo hub , can you hear the fan come up to full song, when they engage , they get very noisy.
Looked between the A/C condenser ant the rad for debris, anything that could block the air flow , EVEN bug screens can be enough to cause overheating.

TeJay · 08-10-2015, 08:01 PM

I find your story utterly amazing. A cooling system on a car, truck, MH, are all the same. They have changed very little over the last 50 years. Yes they are more complex, precise and do have some variations but they work the same. There's nothing really that special about any of them. They all have basically the same components. Why they would refuse to diagnose and or service one is just stupid.

I'm in agreement with Skip426. Here's what may be happening. After the engine warms up a crack is opening and allowing compression (about 800 Lbs) is getting into the coolant cavities that surround the cylinders and combustion chambers. That pressure is building and blowing the coolant out. That is the worst case. It is easily checked by anybody who has the pressure tester. I'd call a radiator repair shop if you can find one.

You said that it's not really getting hot. That kind of makes me think it may be a pressure leak. If the thermostat is stuck then it would be getting hotter. The thermostat allows the hotter coolant into the radiator so it can be controlled by the fan and air moving down the road.

They'll install a pressure tester on top of the coolant recovery tank then start the engine. It will seal the coolant chambers just like the original cap will. When the engine gets hot it will build pressure of about 15 lbs. That's normal. It does that so the boiling point of the coolant is raised, just like a pressure cooker.

However if the pressure continues to rise then you have a combustion pressure leak. Sometimes you can see bubbles in the top of the radiator if you could see it but you can't on the V-10 engine. You may see bubbles in the recovery tank.

If you don't see pressures rising then it may be something less expensive like a bad thermostat as mentioned.

Get it checked and properly diagnosed. I can't believe the shop charged you $300 to unscrew a cap and screw another one on.

TeJay

Excell · 08-10-2015, 08:16 PM

Go on the Ford truck forum .You may get some help there .

Peter27C · 08-11-2015, 06:29 AM

Hi Bob, let's try some arm chair diagnosis. I am not familiar with your year of chassis and some terms used for components can be different so let's get on the same page first.

You have a radiator. On the radiator can be a pressure relief cap or a straight sealing cap. There is a hose that goes from the filler neck on the radiator to a header tank. The new header tanks are plastic. On the header tank can be a pressure relief cap or a vented cap. Or a hose may go from the radiator header tank to the separate header tank.

Our new F53 chassis have a sealing cap on the radiator and a pressure relief cap on the header tank. A sealing cap has no spring on the underside. It looks like a normal radiator cap but when you turn it over it is just a flat cap with a rubber seal.

Let me know what your setup has and we can move to the next step.

The theory of operation is this. And the entire system must have no leaks to work. The coolant in the engine heats up and expands. The extra volume moves up the hose into the header tank. The engine cools down. The volume of water gets less in the engine and sucks the coolant back down the hose.

Problems: any leaks and when the coolant contracts it is easier to pull air in through a leak than pull coolant from the header tank. Now the radiator is not full of coolant. Leaking head gasket/crack, combustion pressure overloads the system pushing coolant and air up the hose into the header tank, forcing coolant out onto the ground. When it cools down there is not enough coolant to fill the radiator.

If you would like to phone me and discuss this send me a pm.

Pete

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tderonne · 08-11-2015, 07:41 AM

Great descriptions above. One more thing.

The expansion/header tank needs an air cushion to work correctly. If one was to fill the tank completely, it would push water out, maybe even "2 quarts".

It isn't overfilled, is it? It should look like this:

Peter27C · 08-11-2015, 08:09 AM

You are partially correct, however it does not need an "air cushion" to work, if every thing is working properly and it is overfilled, yes it will push the extra water out but will only do that the first time as when it sucks back air will now fill the top of the tank.

Pete

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wa8yxm · 08-11-2015, 09:02 AM

Pressure Cap (Wrong or defective) See note
Stuck Thermostat
Serious internal problem (ruled out by pressure test)

OVER FULL RECOVERY BOTTLE.

engine overheat problem.

note: I had a car that boiled over every time we drove it till I replaced the pressure cap.

papasmif · 08-11-2015, 01:40 PM

Hi TeJay
The shop that replaced the cap said that they did a pressure test for leaks and didn't find any. They said that they tested the cap and it was defective. New Cap, filled the antifreeze, did a test run with no problems. They (and I) thought the problem was solved. However I have since found out that the unit doesn't have the problem under low load and/or low speed conditions. I really don't want to go back there at their high prices. They also said that they have no experience with Fords. They are an International truck repair shop.
I am looking for a radiator shop but I don't know if they can hook up a pressure sensor that we can look at while driving with the engine working a little harder. I don't remember hearing the fan kick on. Maybe when going up a very long hill on my last trip but I thought it was the engine/transmission down shifting and running high RPMs. Is there a way to manually run that fan so I can hear what it sounds like.
I looked under the cover and I found what looks like an open port of some type. I will try to attach a picture. It's on the passenger side of the engine at the rear. Do you know what this is ? In any way possibly related to my problem ?
Peter, I can't see any type of cap on the radiator but my view is extremely limited. The expansion tank is now about 1/3 rd full. The level was about half full when I got home Sunday afternoon and things were very warm.

papasmif · 08-11-2015, 01:50 PM

Attaching some picture files. I must have done something wrong before.

ga traveler · 08-11-2015, 02:01 PM

In fifteen years as service manager I ran into this one time. Usually a motorhome overheats in stop and go traffic. This one did fine at idle and stop go traffic. It overheated while at highway speeds. Slow down and no problems speed up and you overheated. We pulled the thermostat and it had broken and jammed at 1/2 open. it was blocking the flow at high speeds. We changed the thermostat and had no further problems.

TeJay · 08-11-2015, 02:42 PM

papasmif,
They told you they did a pressure test and found no leaks. Here's what they did. They installed a pressure tester and pumped it up to 15 or so pounds of pressure and searched for some fluid leaking out. Fifteen lbs of pressure is what the system is under when it's operating. That's fine but it's not checking for combustion pressure leaks. Combustion pressure leaks occur when a crack opens up somewhere in the cylinder heads or cylinder walls and high combustion pressures (800 +lbs) leak into the cooling system and blow coolant out the pressure cap or overflow. I'm hoping that's not what your problem is but it is very possible.

You've replaced the cap. So we can assume it's working. Again it's purpose is to keep the coolant in a liquid state under pressure so it can stay in a liquid state and cool while operating at a higher than normal boiling temp. I'd change the thermostat next. That's a cheap fix and easy to do. Then run it again.

If you do have a combustion leak it may not be necessary to operate the vehicle to far to see the pressure build. Put the tester on the recovery tank. Get the engine hot, run it for a 1/2 a mile stop and check the pressure.

Not having experience with Fords has nothing to do with diagnosing a cooling system issue. Having confidence in their diagnostic capabilities is what's at stake here and obviously they have none or very little.

Change the thermostat or have it changed. Two bolts at the most. Make sure the coolant is full. Drive it up some hills. Listen for the very high wooshing of air. That's the fan clutch kicking in. The clutch fan won't immediately kick in when you go up a hill but the transmission will as it downshifts. The CF needs to heat up before it turns on. That takes slowing down because of the hill and then slowing of the air. Once you crest a hill the transmission will up shift if it's a transmission noise you think you are hearing. If it's the clutch fan it will continue until after you crested the hill and the cooler air eventually shuts off the fan. That's one way of differentiating from the two noises.

Keep us posted.

TeJay

Peter27C · 08-11-2015, 08:58 PM

Had a look under the hood tonight. The header tank is part of an integral system so only has the one cap which is a pressure relief cap. But it works the same as I described.

I would check the fan is locking up at temperature first as it is easier to do than change the thermostat. Open the hood and using a plastic sheet or similar block off the from of the radiator stack. Run the engine with the ac off. As the engine gets hot the viscous fan should lock up with a huge increase in air flow, and a lot of noise. Of course remove the sheet immediately.

Pete

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