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Old 11-16-2010
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Loud thumping and temperature gauge fluctuation

So this has left me scratching my head and I am hoping someone can help.

I have a 1999 4.0L ranger. The problem occurs after the truck reaches normal operating temperature. When driving or when stopped the temperature gauge in the dash will fluctuate from the normal just under half-way mark to around the C. It will continue to fluctuate every 2 minutes or so. After coming to a stop, at red light or parking lot, or after I shut it off the engine I'll start hearing a thumping sound, like a dull bass sound, coming from the passenger side of the cabin. It can be very noticeable or quite subdued. I have gone out and checked under the hood when it starts and noticed that the upper radiator hose will pulsate, and sometimes it has been collapsed. This only happens when the heater is on. If I turn off the air system the thumping dissipates and the temperature needle returns to normal. The bad news is I live in Alaska and need my heater!

The needle fluctuation never occurred until my engine block heater blew out. After getting it back from the shop I noticed the gauge wandering. I've burped the coolant system a couple of times, but it still seems to thump. I replaced the Rad-cap and thermostat. The heat always comes out hot, even when the gauge drops. I am not losing coolant, and have not noticed any coolant in my oil.

I found out that ford released a TSB for a very similar problem and had offered a coolant bypass kit (Part # F8PZ-8522-AA) but my dealer hear said that the part is no longer available and that they no longer have the schematic. Has anyone here had this problem, or had this bypass installed? T

I am not sure if it is relevant or not but on cold starts in the morning this truck also idles a little rough and after leaving the truck idle for five minutes or so it starts running rough and chokes and will stall unless I up the revs. It doesn't seem to stall after it warms up.

It had these repairs:
replaced the bad power steering pump, a cracked serpentine belt, lower rad hose, and had the radiator pressure tested and and flushed in both directions. I got this gunk kind of the consistancy of cat litter, but after that it seemed to run well and the gauge never varied until last month when the block heater became unseated.

Any help would be appreciated!
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Old 11-23-2010
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Has anybody had this problem or had the bypass installed??

If so, could you post pictures? I want to see if I can have the part fabricated, but have no clue what it would look like.

Thanks

James
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Old 11-23-2010
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I've had a truck make a thumping noise and it was the radiator hose collapsing and then opening up.. Must've caused a vibration or the coolant and/or air passing through it may have been making a sort of burping noise? I'd replace that hose while I was working on it if it were my vehicle..

Sorry I can't be of more assistance.


GB :)
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Old 11-25-2010
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ive had the same problem but the thumping was coming from the radiator/overflow... there was air in my system and was caused by my heater core going bad, i live in hawaii so i dont need it. I cut the two hoses going to the core and put them together then bled all the air out of the system by running the truck with the radiator cap off on an incline and kept refilling for around 5min after the thermostat opens... my truck works perfect now, no thump and the temp stays stable between the "N" and the "O"
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Old 12-04-2010
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How about some more info - when was the last time the coolant was changed, what coolant was used? Flush? ...with what? My radiator/cooling system did this when I was having head gasket issues - a Combustion Leak Test would be a good idea. Also find a multi meter and put the negative lead in the block, and the positive IN THE COOLANT. Set it to "AC Volts" and check the reading. .001v is perfect (almost impossible actually), .3v or higher is BAD. That would be Electrolysis - bad thing, just went through that....
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Old 12-10-2010
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I just had the coolant flushed and replaced at my local shop -I am not sure of the brand of coolant they used-, as well has had my hoses replaced. They found that the radiator is leaking slightly at the top and bottom covers - Though it is getting worse now that it is very cold. They suspect that is causing or contributing to the problem. They didn't believe it was the head gasket, but I'll ask about the combustion leak test. I've never head of electrolysis. I'll ask about that too. Are there any noticeable symptoms of electrolysis? I did notice there is some coolant near the exhaust manifold next to the engine. After I got the truck I drove it for a little bit and I noticed steam coming out from under the hood from this area, and still today, but it is far less apparent now.

I think I am just going to take it back to them later today. It is far too cold now to do this in my drive-way.

Thanks for the input everyone! I appreciate it.
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Old 12-10-2010
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They probably spilled coolant on the engine changing the hoses, it will take a bit for it to burn off.

The burping sound can come from air in the system, and you will have air in the system as long as there is a leak. As for the bouncing temp gauge it can be from air or it can be from a cheap thermostat.
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Old 01-26-2011
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Update: I went and got my radiator replaced around the 18th of December. The next morning I went outside and started up the truck so it could warm up. After ten minutes or so I went back out and noticed the new radiator leaking from the covers worse then the original. Took it back and was told the cold (-40F) damaged the seals. Now that it is relatively warmer they replaced the bum radiator. The truck still loudly thumps. After getting home I checked underneath the front end and noticed antifreeze on both sides of the replaced radiator, same spots as before though not as bad, antifreeze was on the fan cowl, and there was a faint smell of hot coolant. I wiped everything down and checked this morning and didn't see any spots in the snow or any noticeable drips forming on the parts. I plan on checking later after the truck cools to see if there have been any other leaks.

I talked to a ford dealer and wasn't given much help about the bypass kit. They found the service bulletin, but couldn't find a part, or a description, or schematic. I was told that the thumping was merely an annoyance but wouldn't cause any problems.

I was curious about this thread:
http://www.ford-trucks.com/forums/91...from-dash.html

It summary it said that the thumping in his truck was caused by a bad power steering pump that was robbing the water pump of power and causing steam. my question is could the AC compressor cause a similar situation? My compressor clicks (I think this is it engaging and disengaging) and whines heavily. It is just a thought, but I thought I'd ask knowledgeable minds.

Thanks for your continued help.
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Old 01-26-2011
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If you think the ac is the issue, disconnect the power connector at the clutch. You may need to zip tie it out of the way.

Power steering pumps are crap from ford, check your fluid if it smells burned get it flushed.
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