I've got a thread going in the Ranger forum concerning a brainbusting cooling system problem I've got. For additional visibility, I'm posting my most recent post here. The URL is http://fordtrucks.com/forums/showthread.php?t=306512. This is a problem that so far I cannot successfully troubleshoot. The probem is noted in the first paragraph below.

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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?

 

Cowboy -

You've identified your problem with 2) - until you fix that leak, the system can't pressurize and let the coolant recovery tank do its job. Hard to believe 2 new radiators have bad/incorrect filler necks that won't let the cap seal, but it sounds like that's where your leak is coming from. If you have the original radiator, match its filler neck against the new radiators(s). Try putting some heavy grease on the top cap gasket, to see if that solves the leak.

Steve

 

Thanks for the feedback. Over the last week I've taken and compared measurements of the radiator cap sealing surfaces on the radiator. I've done it on the current radiator, the last new one, the one that was leaking, and on my two other cars. The distance between those surfaces is consistently 25/32". About 1/2 hour ago I installed clamps on the line from the radiator to the burp tank. Ford never installed any and I've never had a problem until now. I'm not optamistic this was the problem. I also drove it down to a radiator shop for an opinion; they noted the clamps just mentioned and they think I should try a new thermostat. The radiator cap tests good and opens at 15psi per design. I'll probably do the thermostat, but I really don't have any confidence that it will solve the problem. There's no overheating or overcooling.

BTW, the system is developing pressure; removing the cap on a warm engine results in coolant under pressure escaping. It's as if the coolant can't flow from the radiator to the burp tank and by default it's escaping from the top seal on the radiator cap. But the line leading to the burp tank is free flowing in both directions so leakage from the top seal on the cap should not be possible. I'm baffled at this point. It's hard to believe that two radiators could have bad necks. The first new radiator had a build date in 1997 and the current new one has a build date in 2003. Initially, that made me happy; I was thinking there would be no chance of a bad neck due to a the time span between production of the two. The lower sealing surface is parallel to the top one I've taken measurements.

 

Bill -

I assume you've checked it, but is the filler neck nipple for the coolant recovery tank hose plugged? You've blown into that hose and gotten air into the tank? Is the tank's cap vent clear? Also, try the grease on the cap's upper gasket - it's not a permanent fix, but if it works you'll know where the problem is.

Steve

 

I haven't visually inspected it, but I'm able to easily blow air through the hose leading to the burp tank and I'm able to easily siphon coolant from the tank. There is a strong stream of coolant during siphoning implying no restriction. I'm going to go out and apply some grease now to rule out any issue in the neck/upper cap seal. I'll be driving this afternoon and will report what happens. No stone can be left unturned on this one. This includes rigging up a temporary overflow/recovery system from a coke bottle and extra hose. I haven't tried this yet since I'm finding no valid reason to think that the OEM setup could possibly have a problem.

 

Bill -

Obviously the hose and tank inlet are clear from your checks, but how about that hose nipple on the filler neck? Take the hose off and see if it will pass a big drill bit - maybe it's full of solder.

Steve

 

Good catch, but I've checked it with a drill on both radiators. I also just got through lightly greasing the cap seals. I'll most definitely be updating this tread.

 

Bill -

I'm outta ideas - let me know if the grease helps.

Wait........I lied! If you have an old cap, cut off the bottom part and see if coolant goes into/out of the tank with just the top part of the cap installed.

NOW I'm out.

Steve

 

That IS a good one!!!!!!!!!!! I'm gonna do a few warm up/cool cycles this afternoon and see what happens. There may be some hope in those hose clamps that I put on the burp tank line. The level actually dropped some; first time in a week. Experience has shown me that on this rig, it takes about 4-6 duty cycles to fully purge the all of the air out. This is with a good purge to begin with. I'm cautiously optimistic right now. That leak really appears to come from the top cap seal; I looked with a light and a mirror. I'll update soon. Thanks for all the help .

I bought this Ranger new back on 12/4/94. There have never been any clamps on the line for the burp tank. Every other vehicle I've owned puts clamps on this line. I have to wonder if Ford screwed up during assembly.

 

Well, I fixed it and verified proper operation over the last week. What did it turn out to be? I added just one small hose clamp to the burp tank line at the radiator end. The big curve ball along the way became erratic operation. And to think, all I did other than change a radiator was to trim off about 3/8" of burp tank hose so that the hose would fit more secure on the barbed port on the radiator. BTW, Ford never installed clamps on the burp tank hose, by design.

Thanks to all of the good feedback on this one .