Hi everyone. I have a over heating problem with my 86 F-150 4.9L. I do not know what year the engine is as I can not see any code on the block. I know it is from a van as the oil dipstick is sticking up across the radiator. The truck has not run in two years and the WATER in the radiator was brown. I added radiator flush deep cleaning drove 20 miles to town everything ok. Driving around town the temperature started to rise. Started back home and 3 miles from home the engine overheated and vapor locked. Had a friend help tow it home and after it cooled down I drained and flushed the mud out filled with 50/50 mix and it started right up, but started to over heat right away. Pulled the thermostat housing and thermostat was stuck open. Housing was corroded so I replaced it and new thermostat. Still overheated so I pulled the radiator and it was still plugged so I got a new two core radiator and new water pump. When I pulled the water pump the little hole was plugged solid. It took some digging with a screwdriver to clean it out and I fed a wire up as far as I could to open the passage. When I filled the radiator with 50/50 mix I left the upper hose off the thermostat housing and filled till it was to the top of the housing and then replaced the upper hose and filled the remainder. Still hot. After it cooled off I started again this time feeling the heater hoses and upper radiator hose. Coolant is not circulating it was hot at engine, but not anywhere else. So here is the question, is it possible that the engine and head passages are blocked and not letting coolant circulate? While the water pump was off I did scrape rust ***** off of the #1 cylinder in addition to clearing the small hole. I am thinking the flush loosened rust and blocked what little coolant was getting through the passages.

Any ideas as to how I can clean the rust out of the passages? Or any other ideas.
Thanks, John

 

Hey,

I would back flush the system vigorously. Use a garden hose and flush solvent. Purge/bleed air from system. Also, verify you got the right water pump --EFI pumps (Serp belt 87-96) spin opposite to the Pre-87 versions. Rad cap good/ on tight?

Finally, how do you know its overheating? 30 year-old stock gauges can be unreliable

 

Just cause a T-stat is new does not mean it is any good. I can't count how many I have got that were bad from the get go. So do not rule that out. I now test all thermostats in hot water before installing.
Additionally try running the engine with the rad cap off sometimes they get an air lock in the them and this will help purge it.

 

I like the idea of back flushing with a hose. My water pressure is 50+ psi. I will pull the water pump back off, block the heater core ( I did flush the heater core with the hose before) hook the water hose to the upper radiator hose and see what comes out. What flushing solvent do you use and how do you circulate it while back flushing the head and block ? I do not have a Serp belt, It has the old fan belts with a fan clutch and solid fan blade. The fan clutch screws onto the water pump with left hand threads. How can I tell if I got the right water pump?

Besides feeling the heater and radiator hoses I also used a inferred hand held gun. I had 300+ at the thermostat housing and 84 at the upper radiator hose by the radiator tank. I could also feel it boil in the heater hose.

Thanks for help!

 

I forgot to mention that I pulled the thermostat out and tried to run it without one. It still did not circulate.

I filled the radiator with the upper hose off till coolant started to come out the thermostat housing and installed the upper hose and topped of the radiator so I don't think there was any air lock.

Do not know how to check it I have the right water pump. Do you know how to tell?

Thanks

 

300+? In the immortal words of Frank Zappa: "Yowzah, yowzah, yowzah!"

That's hot! If the radiator inlet is only 84, that certainly sounds like a lack of circulation.

A clogged radiator could block circulation like that. A quick test for total blockage is to fill the radiator completely with water. If the cap is on the downstream side, away from the inlet, you'll have to remove the upper hose and fill it from there. Then disconnect the bottom hose and observe how quickly the radiator empties itself. Don't get misled by water coming from the lower hose, as that is coolant leaving the block. You want to watch the coolant draining from the radiator. No exact specs for how long it takes, but you should see a very healthy rate of flow. If not, your radiator is clogged. No amount of backflushing will help if clogged that badly.

If that checks okay, then +1 on the previous comment that your new thermostat may be bad. You can briefly run without one as a test, but don't leave it that way. Make sure the thermostat has a small hole in the flange, too. This helps the hot coolant reach the thermostat so it can open on schedule.

Does the straight six have a coolant bypass hose between the water pump and thermostat housing? In a recent thread, a V8 overheat was fixed after finding this bypass hose kinked shut. The bypass hose helps hot coolant reach the thermostat so it can sense when to open.

 

I have a motor, non-Ford, that when I got the car had mud for coolant and I mean MUD!
After a flushing with a 2 part for a week it still over heated. I found there was no stat when I went to change it out, still over heated.
Replaced the radiator (2 times) water pump all hoses and flushed again, yep over heated.
Even add a fan shroud, car never came with one from the factory as the fan is about 2" from radiator. It did help keep it from over heating longer but it still over heated.

Every time it pegs the gauge and you shut the motor off you can hear the coolant boil in the block.
The cooling system is so bad 3 core plugs have rusted out of the block and 1 in the head, yes the head!

What I think is happening is there is still a lot of mud in the bottom of the passages around the cly. you can see this when I replaced the core plugs and tried to clean it out.
This mud will not let the coolant pull the heat from the cly.walls.
Had a buddy that had a junk yard motor that ran hot, not over heat but hot. He pulled the motor apart and found mud flushing would not touch in the coolant passages.
He had it hot tanked and no more hot running motor.

I think that is what part of the cause of over heating is on mine and like you said it my have passages between block & head plugged.
Only way to know is to pull motor and hot tank it but in my case it is a PITA to pull in this car so it is parked for now.
Dave ----

 

I had never heard of a engine that had sooooo much rust that it could not be flushed out. I am going to try and back flush the head and block from the thermostat housing out the water pump opening. I will let everyone know how it turns out. If not then I will pull the head.

Thank for the information. It confirms what I have been thinking. Blocked passages.
John

 

Before you pull the head just pull the water pump (much easier to do) and back flush with the pump off through the thermostat. You are going to need a large volume of water to properly flush generally the garden hose will not quite cut it unless it is a high flow tap/piping. If that does not do it pull the head and flush down each coolant passage to the bottom in the deck surface be sure to leave the water pump off. Back in the day they would use something like a zoo flush gun with a copper pipe extension to get down to the bottom of the engine casting through the coolant passages in the deck surface. A solvent gun hooked up to water with an extension should do the same thing.

 

I agree. I will pull the water pump first. I think I will video the gunk that comes out and put it up on YouTube.
I want to check out the new water pump to see if it looks like the old one. Make sure the fins are in the same direction. I was told that there are 4.9L water pumps that flow in different directions. I did not know that.

Thanks
John

 

Ya the reverse rotation ones used with serpentine belts. Ha would not surprise me if the parts place gave you the wrong one. Not like that has ever happened
It would explain the over heating though.

 

Um, before you convince yourself of the worst, most expensive scenario, may I humbly offer my personal motto. It has served me well over many years as a professional mechanic:

"As little as possible, for as long as it takes."

You've received some good suggestions so far, but they are just that: Suggestions.

Latching onto the worst case scenario, at the expense of other less awful choices? That's like asking, "How can I make more work for myself that may not even fix the problem?" Now if you prefer that, I'll humbly bow out. But if you'd like to live my motto ( it rocks! ), then come up with a plan. Work based on the symptoms right in front of you, versus what you have a hunch might be the problem. Chip away at the free and easy stuff first before digging too deep.

Let's say your poor engine is partially clogged with crud. Hopefully it's not a solid piece of sludge and rust yet, but it could be better. If the water pump is actually circulating the coolant/sludge mix (or at least trying), where is it going to collect first? In the wide passages inside the block? Or the narrow passages inside the radiator? That's why I suggested doing the simple flow test of the radiator. Ten minutes and a garden hose, that's all you need.

If good, then you're probably looking at a pump problem.

If medium okay, the rest of the block may be okay. You'd only need to replace the radiator or have it professionally cleaned. Remember, the garden hose flush method ain't going to do much for the radiator, and mostly just run up your water bill.

If the flow is severely restricted, then you may have a lot of crud in the block, too. That could get expensive.

See how that worked? Ten minutes with our friend Mr. Garden Hose and you've settled on one scenario and ruled out the other two. Hopefully you'll save a lot of money in the process. I'm not too proud to split the savings. 60/40? Or are you okay with 30 percent?

Respectfully submitted.

 

KR's got the right idea. I too like to start with the quick and free tests before trying more expensive and time-consuming solutions. My 4.9 always ran hot until I flushed forwards, flushed it backwards, and flushed it some more, up down, sideways....you get it. You'd be surprised at the crap that fell out. Sand and bailing wire left over from the casting process.

Your new thermostat probably got cooked at 300 F, get a new one of those too. And check the direction the water pump impellers spin, they may have given you the wrong pump.

 

KR , I love the " Danger Will Robinson! " I remember the show well. The radiator was plugged so I got a new 2 core. I replaced the water pump because of the crud in the output. Good that I did as I had to chisel out the small hole that was plugged. Now I will pull it off and check the rotation to see if it is the same as the old one.

I have time and water so I will be flushing forwards and backwards. You can bet I will be testing any thermostat before it gets installed.

Thanks Guys,
John

 

Hello Everyone,
Overheating problem solved.
This is what I did.

I removed the water pump and it is the same as the old one. The impellers (fins) are straight out from the center. Not slanted to the right or the left. I flushed and back flushed till clean. Filled with water till it came out the top radiator hose started and run till I could tell it was pumping and connected the hose. It no longer overheated. Drained the water, filled with antifreeze with the upper hose off the thermostat housing till It started to overflow the housing. Filled it very slowly and watched the air bubbles come to the top. When the bubbles stopped I connected the hose and finished filling the radiator. Air blocks in the upper hose so I keep squeezing the hose to get air out. When I got no more bubbles I put the cap on and run the engine a little. Let it cool and removed the cap and added more coolant. Run engine a little more let cool and radiator was full.

No more over heating!!!

Thanks everyone for your help!

John