My 93 Ranger (3.0L) has a thumping sound coming from my cooling system. The thumping only occurs when I'm driving at highway speed, during cool weather AND WHEN MY TEMPERATURE CONTROL LEVER IS IN THE HOT POSITION!! I know this sounds weird but it's true. I can make the thumping sound go away by simply sliding the temperature control lever to the COLD position. Within a minute or two the thumping disappears. I was told of a TSB that indicates I may need a coolant bypass kit because built up steam has nowhere to escape. And I'd probably be talked into the kit if it wasn't for the fact that the thumping sound seems to be influenced by the temperature control lever. Any ideas out here? I'm slowly loosing my mind over this.

Rick

 

The bypass system has a heater hose size fitting near the thermostat housing that returns coolant to a T fitting in the lower hose. The idea is that the heated coolant on the engine side of the thermostat
has some air or steam in the system that finds it way into the heater core and causes the thump noise as coolant flows through the core. The bypass returns the air/steam back to the lower hose to be sucked back into the water pump with cold coolant from the radiator. It works. Don't know why only the 3.0L experiences this condition, might have something to do with the engine running at a higher RPM and water pump speed then the other Ranger engines. By sliding the temp controller to cold, you allow outside cool air to go through the heater core and essentially condense the air/steam to not be as obvious.

 

The TSB is #96-21-12.

 

[updated:LAST EDITED ON 10-Oct-02 AT 02:14 PM (EST)]Thought I read something on the 4.0 having the same problem. I have a `99 3.0 so this issue concerns me greatly - haven't got the $ for a bypass kit... PLEASE keep us informed... Glenn

 

An update. The last few days have been cool - right around the freezing mark. I live in Canada. I still hear the thumping sound and everyday I check the coolant levels, etc. The coolant levels are always good. However, this morning I noticed that the coolant overflow tank level had been sucked down guite a bit overnight (almost dry). Could I have had a air pocket that was causing my problems? I'm going to run it today to see if the thumping is still there. Thanks for your insight guys - I appreciate the help.

 

Yes, air in the cooling system will cause a thumping sound.

 

Hey, check out the post entitled "Additional details on TSB95128". Some good info.
:7

 

The engineer I work with just fixed this problem. He consistently had air in his cooling system. Turned out just as I suspected, blown head gasket was allowing air into the system on each compression stroke. We yanked the head, planed it for a couple more lbs compression, replaced the head gasket.... no more probs. Doubt this is the problem on your 3litre. A quick indication is a compression check. Look for a low cylinder. Also, does the coolant barf out the overflow?

I have solved the problem of gassy colling systems in the past by drilling a 3/32" hole in the thermostat. This will allow the gas/steam to pass the thermostat and enter the rad, be cooled and turned back into a liquid. Some thermostats have a hole and a little brass one way valve in them for this reason. If your thermostat has a brass valve in it, yank it out and drill a slightly bigger hole.

There is also an additive used in diesel engine cooling systems. I believe it's called anti knock. Diesels burn so hot that the coolant will turn to vapour in spots on the sides of the jugs and cause hot spots that can burn the piston. My father has been into the heavy duty stuff for decades and says it's quite common, especially in Detroit diesels.

I'd try the cheap things first, drill a hole in the thermostat, and try some anti knock additive. Check that compression and reservoir levels to make sure you don't have a blown gasket.

Rick

 

The main problem is FORD didn't put a by-pass on these 3.0 engines.
The TSB Ford put out adds a by-pass into the system. My first indication of a problem was when I bought my 94 new and the temperature gauge flucuated erratically(up and down continuously). Worse in cold weather. They installed the bypass kit on mine for free and the problem went away. Now on my 3rd radiator and back to original hose configuration I am getting the noise that I never had before. I also drilled a 1/8" hole in the latest Robertshaw thermostat to try and get some flow by the sensor on the stat. Just yesterday saw the upper radiator hose sucked almost closed and then go to pressurized?
Sure wish I knew the answer, but the TSB (96-21-12)does help.

 

[updated:LAST EDITED ON 22-Oct-02 AT 09:34 PM (EST)]Yeah - we need an answer to this - cooling systems are "basically" pretty simple - aren't they ? PS - Has the design changed since `93 - `94 ? I have a `99 3.0

 

 

Did you guys ever get this fixed? I have a 99 4x4 3.0 with a similar problem, in addition to the noise it over heats when climbing long grades in the mountains. I really need to get this fixed. Radiator has been checked and system pressure checked, flushed, new 180 thermostat, new radiator cap, new ford clutch fan and still the same problem.
Did installing the bypass kit fix your problems? Thanks for your time, Jon,
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