Two 4.0s getting hot

[stx4.0]

I bought 2 rangers last year from different people that got them hot.I got good deals on both but am having trouble fixing the overheating problem.One is a 4wd that the water pump went out and went out bad from what I was told.I guess it lost all coolant within minutes out the weep hole.Anyway I pulled the heads and one of them was cracked,neither one was warped though which was strange as it got hot enough to pop the overflow hose off and spray coolant everwhere under the hood.I bought new alabama cylinder heads and put a straight edge on the block and the block checked out so it all went back togeather.I also had the radiator cleaned just for insurance as it looked really clean anyway and bought a new thermostat.After I put it all back togeather and fired it up it still wants to get hot and acts like theres no coolant at all in it.Once the temp gauge starts to climb it keeps going.I pulled the thermostat out and ran it that way and it had no effect which really puzzles me.My only thought now is I had to miss something when I put the straight edge on the block even though I was very thorough when I done it.Does anyone else think the block is probably warped or is there some trick to the 4.0 I dont know about?I am holding off working on my other 4.0 untill I know for sure how to fix the problem.I also pulled the thermostat out of it to see if it had any effect and it did the same thing the other one did.Anyone got any ideas or thoughts on anything I might have missed?

 

[Beanmachine7000]

If it still gets hot with no thermo, it sounds like coolant isn't able to flow... Have you made sure coolant can flow through all the passages in the heads and block? You said you replaced the heads, but what about the water passages in the block?

 

[ranger dude]

I have seen this only a few times that the water pump impeller was rotted away or had broke loose from it press fit one way to comfirm it is if the thermostat it out take the rad cap off or upper hose at the rad. and check for flow with engine running the rad cap way is less messy it so be flowing good even at a idle if rpm is rised (1500-2000) it should be flowing strong and level in rad sould drop 2-3''

 

[stx4.0]

The water pump was replaced with new as it was the reason it got hot in the first place because of it failing.The block passages were fine,no buildup at all around the holes.I made sure every one of them was totally clear since the heads were off.It does actually flow coolant as I felt the radiator hoses as it was warming up.That was my suspicion also was that no coolant was being circulated.It seems to flow normally.I ran the heater also while it was warming up and it did get warmer as the temp gauge climbed so I know the coolant is defineately flowing and also the temp gauge reading right.That is why i wondered if 4.0s have to have something different done(besides the basics)if they get hot.I am really thinking the block is probably warped at this point but dont want to tear it back apart unless I am sure.

 

[RangerSVT]

Usually when an engine gets hot, the rheostat inside the temp sending unit gets stretched and the guage reads incorrectly, it's cheap insurance, but try changing the sending unit, or put a mechanical guage and see where that gets you. Try flushing the coolant system with clean water for 15 min. Turn your heater to full hot, open the drain pet cock on your rad(remove if possible), and put your garden hose into the rad and start your truck and flush.
SVT

 

[stx4.0]

I actually did all that right off the bat.I did think the temp gauge was reading wrong,that is untill the radiator starting boiling over!Then I knew for sure it was reading right.Which also told me I probably just ruined a new set of alabama heads!This was after I had ran it 2 previous times and shut it off-to be cautious-when the temp gauge was showing it was getting warm.The third time I let it run and kept my eye on everything.When it started boiling over,it went!It popped the cap on the overflow and from there sprayed coolant all over the place.So I defineatly know the temp gauge was reading right!

 

[RangerSVT]

Do a compression test and leak down test and see if you have any probs in the cylinders, retorque the intake manifold in sequence to the heads, check your oil level for contamination, such as coolant leaking from the intake.
SVT

 

[stx4.0]

I did a compression test after I was done installing the heads.They were all exact except for the cylinder that had water in it from where the original head had cracked and let coolant leak in.It had some rust in that cylinder that I had to remove but it wasnt bad and the reading was only a couple pounds less than the others.I didnt however retorque anything,other than what the Ford manual or fel pro gasket called for.I wouldnt think that would cause overheating though.As far as the block and radiator everything was flushed and cleaned when it went back togeather.The coolant passages were pretty clean in the block and I did not have any problems at all with overheating before the water pump went out.That is why I am thinking the block is warped now.I know this is the only vehicle I have ever owned that I could go out and start it when the temp was 0 and have heat blowing out 2 minutes later.That always amazed me.

 

[RangerSVT]

I had a similar problem with a 4.6L in a 97 cougar, engine overheated, put another block in it with same "plastic" intake, and still overheated...I didn't check it out but lead me to believe that the intake was damaged, possibly warped...I'd check the mounting surfaces of the intake to head and head to block, maybe something is warped, thats the only thing I can think of left...
SVT

 

[dorman68]

Is the heater core clogged? I have seen other cars overheat because of a partially clogged heater core slowing down coolant flow.

 

[stx4.0]

I think you are right Ranger svt.I think something is warped somehwere..I tried to cover all other bases on this.I never checked the upper or lower intake for warpage but I wouldnt think they would cause the motor to hold that much heat being made from aluminum.I think it is in the heads or block,maybe both.As far as clogged heater core it throws out heat like you wouldnt believe.I wouldnt think a clogged core would do that.Not only that all the test I have done so far show the coolant circulating fine.I was told the other day by removing the thermostat I didnt help its ability to cool..The guy said I wasnt giving the coolant enough time to flow through the radiator to dissipate heat??I never heard of that before..Any other motor I was ever around that had a removed thermostat it took awhile for them to heat up and then they would not run as warm as usual without it.

 

[RangerSVT]

The theory on removing the t-stat can go both ways...yes it will take a while to warm up as the block constantly has a supply of cold water, on the other hand with no t-stat to slow the water flow down, IE restrict the flow, the water can in theory flow too fast past the cylinders to transfer the heat from the cylinder walls to the water, thus cooling the engine...aluminum can warp quickly, especially with enough heat, that can in turn cause both heating and cooling problems...
SVT

 

[289-tiger-]

Check or bypass the heater core (maybe cavitation) one line cold one line hot = problem.

Good luck.

 

[stx4.0]

I can tell no matter how hard I try its still going to end up in me tearing this animal back apart and I dont really mind that as much as long as it ends up fixing the problem.I think the whole thing is going to come out this time.As hot as it got I think everything should be checked.I always worry about piston/ring damage on an overheated engine,especially with the tolerances these engines are built with.I never really looked at the angle that maybe the intake could be some of the problem.If its not warped I will be surprised.I will say this.I did not like how the fel pro intake gasket was made.It is flat and you have to form it yourself as you drop the lower intake into place.It is really awkward and cumbersome.I think the factory one was ten times better.I was told by a ford mechanic that they can be reused if your careful on how they are pulled??Dont know for sure if thats true.I never like feeling I'm taking a chance especially with a gasket so I used the new fel pro.I often wondered if it didnt seat right but I never had any leaks.

 

[RangerSVT]

Did you try a gasket from FOMOCO?? Maybe the dealer will have the style you are looking for, as for what my opinion is, I would not reuse a gasket, you have it apart anyway, replace it with new and do the job right the first time. IMO, too much of a chance to take
SVT