On Wednesday I replaced my radiator under warranty due to leakage from one of the tanks. It's the correct radiator for the application. The cap was new OEM from Ford in April of this year. The cap is the correct pressure for the application. All was once fine other than the slight leak. Simple enough. But now, for some odd reason the new radiator is not purging itself of ANY air via the burp tank, and does not draw ANY coolant back in when the vehicle has cooled off. I properly purged as much air as possible during refilling of the cooling system. I've never seen this before in my life. Anyone been down this road before?

 

Make sure the hose from the top of the radiator to the overflow reservoir is not pinched, or clogged. The next thing to try is replacing the radiator cap again.

 

My 99 4.0L came from the factory with the overflow hose pinched shut underneath the air box, so check there.

When the engine would cool off, the radiator hoses would collaspe.

 

The hose leading to the burp tank is fine. I trimmed about 3/8" off it at the radiator to ensure a good seal and there are no kinks in the line. The hose must be removed from the top of the radiator while doing the radiator swap so I personally inspected it during reinstallation for damage and correct routing. I'm gonna swap out radiator caps with another rig of mine and see what happens. Do remember, other than a slight leak in the old radiator everything worked just fine. I'm confused that simply installing a brand new radiator, all parts being correct, and the system well purged has resulted in this issue. I'm hard pressed to think that there could possibly be something wrong with the radiator; I can't imagine what it could be. Never in my life have I seen this happen.

 

Well from your description's of what has been done & checked, then it seems we are left looking at the filler neck on the new tank.

By that I mean, it seems maybe someone put the wrong neck on this radiator tank at the factory & it's such that, with the cap installed the system can't physically equalize itself.

Are the depth dimmensions & other physical configurations in the area where the cap fastens & it's plunger seal makes, down in the filler cap area, the same as the OEM or the last Modine tank you had on????

Just seems from your description it's a configuration or dimmensional problem where the cap fastens on. or some weird unheard of internal assembly thing.

 

Bad deal; I can't check it. This is only the second time in my whole life I took in the old part and came home with the new one. The old one is gone. I've been bit like this both times. But from the feel of the cap when it's being installed, it feels normal. I know, that in itself still isn't good enough.

 

Well lets see, do you have anyone close by with the same engine/radiator combo, that you could compare it to????

Just thought of something else, do you suppose the over flow tube was plugged at the factory, to keep debrie out during shipping & that plug got pushed deeper & out of site such that you couldn't see it & is still in there???

 

Tube in the radiator should be ok. When I loosened the cap, air/coolant was released into the tank. But still would be good to poke something through that tube.

What I think I'll do is see if the parts house sent the old one back to Modine yet and prey they still have it qround.

 

An update and request for ideas. The situation was and is such that, after the cooling system has been purged of air as best possible, with the nose of the vehicle higher than the rear, the radiator will not displace remaining air/coolant into the burp tank when hot, and will not draw coolant from the burp tank back into the radiator when cooling (engine stopped and vehicle sitting overnight). It behaves like a solid cap with no venting ability is installed. So far I've:

1) Checked discharge port on radiator that leads to burp tank for obstruction. The port is clear and free flowing.

2) Hose from radiator to burp tank is not pinched or obstructed.

3) I have two cars plus the Ranger; I've swapped radiator caps on these cars onto the Ranger. Their pressure rating was the same. They were all funtioning correctly. No change on the Ranger.

4) Went to Ford dealer and swapped out the new, OEM cap I bought last spring for a new one. No change.

Today I contacted the suppler for the Modine radiator and told them the story. Reluctantly and with a bit of pressure from me, they agreed to get a new one in for me.

So now my questions: has anyone experienced anything similar/like this before? Has anyone ever seen a defective/improperly formed/incorrectly indexed radiator cap seat on a plastic tank on a radiator that has resulted in a situation like this? Remember, other than a small leak on the old radiator, all worked fine. Coolant lost due to the small leak was replaced at the burp tank as should be.. Replacing the radiator has now resulted in a new problem while the leak is, of course, gone. I've never seen anything like this in my 27 years of working on vehicles .

 

I forgot:

Item #5) Distance from the lower seating surface of the radiator cap seal to the top of the cap (seating/seal surface) was measured on the Ranger as well as my two cars. Distance is consistently 25/32".

 

Well pawpaw has tinkered with vehicles for 50 years now & in all the years I've had vehicles with closed systems with recovery tanks, I don't remember having this problem nor hearing of anyone who has.

Good feedback Bill.

Will be interesting to see what happens with the replacement tank.

 

This is a new one for me too, good luck with getting it corrected.

Do you get flow through the radiator?

 

Thanks for the feedback guys.

There is good flow through the radiator and no cooling or overheat problems. I just got back from the parts house where I bought it. I took six pictures of the radiator cap area on my old radiator as well as a measurement between the two surfaces that are sealed by the radiator cap. Same distance, 25/32". A few more pictures were taken of seemingly significant dimensions (scale in the picture). As soon as my truck cools and ample opportunity is given for any liquid to be returned from the tank back into the radiator (lol, good luck, I've been adding coolant in 3-4 ounce increments the last few days) I'm going to look at the orientation of the cuts on the radiator that align the cap and compare against the pictures. I'll update as more information surfaces.

I can't believe something as simple as installing a radiator can throw a guy a curve ball like this has . My fingers are crossed that the next new one takes care of the problem.

 

Well, yesterday I replaced new radiator #1 with new radiator #2, another brand new Modine. And..................the problem continues . The burp tank is not receiving coolant on a warm engine, nor does the level in the burp tank go down when the engine has cooled off (overnight). There are a few more things to add to this story (headache):

1) When installing new radiator #1, I trimmed about 3/8" off the hose leading from the radiator to the burp tank. This was done to remove the deformation in the hose caused by the barb on the port leading off of the radiator. Over time, the barb causes a slight deformation in the hose and I wanted to ensure a positive seal. On the other hand, I can see no reason how this could contribute to the current problem.

2) On new radiator #1 and #2, I've noticed that coolant is somehow escaping past the upper seal on the radiator cap (as best as I can determine), running down to a small plastic protrusion on the tank just under the port for the burp tank, and dripping onto the lower radiator hose. Trace amounts of coolant are also noted running down the radiator tank. I think heat dries much of it off. This explains why I loose about 8 ounces of coolant the first time I drive it after filling.

3) FWIW, all radiator and heater hoses were new in spring of 04.

4) There is no evidence of overheating or overcooling (ie, bad thermostat).

5) There is no reason to believe that by coincidence a head gasket blew at the same time the radiator was replaced. There is no foam/bubbles in the coolant and it's not pumping coolant into the burp tank. And of course, the burp tank is not overflowing.

#2 really would make it seem as if there is a problem with the radiator cap. However, it's a new cap from Ford. The current problem occured with the previous cap (OEM Ford, new in spring of this year and working fine prior to radiator replacement) and I've ran two radiator caps from my other cars, both known to have no problems. The problem persists with all radiator caps used.

At this point, I'm concerned about the possibility of abnormally high pressure buildup in the radiator which may result in blowing the new radiator and/or the heater core. I've noted that on my other two cars, I can squeeze the upper radiator hose and coolant is driven into the burp tank. When I release my hand from the radiator hose, coolant returns from the tank back into the radiator. When I do this on the Ranger, no fluid is expelled from the radiator nor does any return. Do remember that I've verified that the line from the radiator to the burp tank is not obstructed or pinched.

At this point I'm baffled. Two new radiators, four radiator caps (one being new), a perfectly good/functional line between the burp tank and the radiator, good radiator/heater hoses, fairly new and correctly functioning thermostat, and no evidence of a head gasket failure. How can something so simple as a cooling system be causing such a headache?

On edit (5:18AM 11/19/04)....

There have been two random times where coolant was expelled into the burp tank; it never returned to the radiator. This happened after the radiator was filled. Filling the radiator will not consistently make this random discharge into the burp tank occur. Last night again proved that.

 

WOW, you are having a rough time Bill!!!

Just a dumb question, if you disconnect the line to the burb tank from the radiator, holding it lower than the tank, does coolant run out?????