radiator / pressure/ problem

[remote]

recently my backup 89 f-250 developed a seam leak around the top of the radiator. Because it is a backup truck it is not driven regularly.
I suspected that the seam leak was because of pressure when it appeared but cant confirm it. Today I drove the truck to town which is about 6 miles. I didnt check the water level even though I knew the seam leak was there and simply forgot to check. When I arrived in town and stopped
I noticed that the truck had a small amount of steam coming from under the hood. I figured that the seam leak showed up more in cold weather we have had in the last couple of days so I was going to wait till I got home to check and fill the water level. On the trip back I noticed the thermostat run up way higher than normal but not to the hot level. I then heard a single thump or pop and started smelling coolant but the thermostat guage fell back to the normal position. I was only about three miles from home so I continued but when I got about 400 yards from the house the indicator went to the hot side and the engine hot indicator light lit up. I went on to the house and filled the radiator up with water and cooled things down. The motor was running hot but was not to the point where it would blow back water from the radiator.I did notice that the radiator was swelled out around the top where the seam had been leaking. To replace or fix the radiator may not be the original cause of either the seam leak or the swelling. Below I list what I think are the possibilites of the problem but If anyone could help me troubleshoot I would be thankful.

1. radiator cap not functioning.
2. thermostat sticking.
3. Leak in the heads or gasket causing the radiator to pressuize.

[Snotzalot]

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I was only about three miles from home so I continued but when I got about 400 yards from the house the indicator went to the hot side and the engine hot indicator light lit up.

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Why would you ignore something like this??????? You could have been merely low on water, if you filled a hot engine too soon you could crack the block etc. I'd fix the radiator, fill it up and then takle it for a test drive.

[OkieGringo]

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If anyone could help me troubleshoot I would be thankful.

1. radiator cap not functioning.
2. thermostat sticking.
3. Leak in the heads or gasket causing the radiator to pressuize.

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All three a possibilities, of coure. But you just need to get the rad fixed first. I had a similar seam leak, cause by poor solder joint when I had the 5-row core put in in Baja. I took it out and to a rad shop(15 miles away) to have it fixed. The guy suggusted that I use a 7lb cap(he gave me one free) rather than the OEM 12lb. He said that using a higher pressure cap just puts too much strain on all the system and if the engine gets soo hot as to need that much it's already too late and way past safe for engine. Pressure cap increases boiling point 1.5 deg/1lb of pressure. Water boils at 212+(12x1.5)=230. A 50/50 mix Antifreeze raises boiling point to 265 deg(way higher than I EVER want to see my coolant temp), add the (12psi times 1.5psi cap=) 18deg and you're up to 283 deg [img]/ubbthreads/images/graemlins/eek.gif[/img]. OkieGringo

[jlrsn]

I used a 16 lb cap for years until last month when I dropped it to 13 lbs. The 16 lb cap was put on 6 years ago when my SO took the truck in for a starter when I was out of town.

[Runboy]

Interestingly, I didn't ever even think to check the cap on my truck till the other day, remembering this post. I was getting a bit worried about what seemed to be some slight seapage out of the top radiator tank seam. Previous owner had replaced the radiator (Czech Republic special), but I still didn't feel it should be leaking that soon.
I also had issues with the ranger heater bypass valve leaking at the hose connections and where the shaft enters the body. As well as a leaking top radiator hose to thermostat housing which finally quit seaping after repositioning the clamp several times.
Well, the previous owner had installed a 16lb rad cap! I went looking through the parts books and my truck (89) called for a 7lb. 90 they went to 12lb and super duty called for 16lb if memory serves correct.
Anyways, cap has been replaced with 7lb and I am curious to see if some of the top tank seapage issues are resolved.
Mike

[cdnsarguy]

Runboy ..quite often a newer hose has been punctured with those hangup strings. This is a good leak point placed usually right where we try to get the best seal on the hose. One must remember to either mark those holes before install or go back a bit further with the clamp.

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(Czech Republic special),

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Mine was a new Ford rad from the same place first upper seal leak came 3 days past 1 year warranty...... [img]/ubbthreads/images/graemlins/eek.gif[/img]