overheated 4.0

[FR-425]

Wrong head gaskets blocking the water ports? Installed backward?

I think you would have to be near blind to put them wrong way round, but it is possible.

 

[stx4.0]

Yeah I know.I made a comment to that earlier about triple checking those but yeah no real excuse to put those in wrong.Thats too big of a job to goof up.They were definitely installed correctly and I do always check to make sure they were not labeled wrong so in other words I didnt just look for "top front" etc and stick it on there..I checked to make sure the coolant ports were lined up and nothing was blocked off.I think I'm going to have to end up changing the engine in it which I hate to do as I know it has very little wear.I've never had an issue like this one where there should be an answer somewhere if you cover all the bases.I am going to play with it a little more and see if I can turn up something but I have been out of ideas for awhile.That is why I posted the thread.I though some different brains might have an answer I hadn't thought of.A guy at ford told me they had a 96 explorer in one time that they couldnt stop from overheating and they ended up putting a new long block in it but I don't know how hard they looked for the problem.doubtful they looked very hard..most dealers I think would rather take the more expensive route to fix something if they have someone willing to pay for it.

 

[2stroke]

I figured I would put my input in, as we had a car that was the same way. We bought it cheap, and was told it just needed a water pump. As best as we could tell, that was all that was wrong, and we really looked that car over before buying it. Long story short, the previous owner "forgot" to tell us he dumped about 5 bottles of radiator stop leak in to stop the leak. The heads were fine on that car too, just a water pump leak. After we finally figured it out, we got a new junkyard engine, put it in, and drove the car a good 150k miles before it rusted out. I think what we did was block off every coolant line except the radiator hoses. We took the thermostat out, and the only path the water could go was through the block. We could not get water to pass through the block with garden hose. We tore that engine down and found water jacket caked with stop leak. The only thing is we noticed it right away when we took the heads off. You probably would have seen it. Anyway, my bet is for a major blockage.

By the way, removing your thermostat will always make your truck run cooler. There is this theory about thermodynamics that says there is a point of no return where your water is being pumped faster than the radiator can cool. While this theory is actually correct, it does not apply to engines in the real world. Real world race engines often run with no thermostat. Thermostats provide one function, and that is to provide the minimum running temperature.

 

[stx4.0]

Thanks for the input.That was always my feelings as well was they would run cooler without it.I tried it in mine and was called an idiot lol by several people and thats when I was told one of the purposes of that thermostat was to slow down the flow to the radiator so the coolant would have a chance to get rid of its heat as it passed through..I tried it in mine and it had no effect what so ever when removed...once the temp gauge starts its climb it will go until pegged out.I do know my block was pretty clean.As I mentioned already when I had my heads off I looked down into the coolant ports in the block and they looked great.I still flushed it out with a hose while I had everything apart just to get anything loose out of it.But the guy I got it from was honest about it.He told me about the pump going out and driving it several miles with no coolant.Normally the pump will seep when they go out and give you plenty of time to change it but according to him it had a major failure and spilled everything out pretty quickly.He told me I would probably have to put an engine in it.I got it cheap enough I can put up with the aggravation its caused.Its just anything I've ever worked on thats overheated you can always fix it as long as its not cracked and if its warped that can be fixed also.This engine has a ton of miles left in it if could figure out whats going on.I am at roadblock at this point on whats left to check.

 

[natenkiki2004]

Chances are, it's not going to be the clutch fan. I believe when the clutch usually fails, it locks the fan so if anything, it would over-cool, not under-cool.

Radiator could be a possibility, slow flowing. Did your friend with the temp gun go over the entire area of the radiator? Top to bottom, left to right.

 

[vq5speed]

Well you can check your coolant flow. I just did a complete cooling flush couple weeks ago. I took out the thermostat put it back together ran radiator flush additive through the whole system. Then I unhooked the upper hose and lower hose and ran the water hose into the top hose into the motor and watched it flush out the bottom. You could just do that step and see if water flows out the bottom hose.

 

[natenkiki2004]

Here's what gets me; the temp sensor is in the lower intake manifold and according to your infrared/laser reader, it's reading the right temperature. That means you MUST be getting flow from the block, through the heads and into the lower intake manifold. Have you felt the return hose at the bottom of the radiator to see if it's as hot as the input?

I'm really curious though if your radiator is plugged up pretty bad. If you get bored, you might try a test; Remove the radiator, plug the lower hose port and close the petcock. Fill it up with water through the upper hose port. Un-plug the bottom hose port and keep filling it through the upper full blast with a garden hose. If it's flowing correctly, it should not over-fill. Meaning, it should drain faster than you can fill it.

Another thing to try if you've got nothing else to try, get a bottle of Prestone flush. Put it in with water and run the engine until the temp gauge is about the N/O area (no need to overheat). Let it cool, run it again, let it cool. Do that a few times and see if it gets any better. If not then there's gotta be some kind of serious and unmovable restriction somewhere.

 

[stx4.0]

I can't remember now if we felt the lower hose or not,we likely did but not sure.I know water was circulating through the engine as we did more than enough checking on that.As far as blockages I can't see where there would be any as the engine doesn't have a pile of miles on it and was clean inside.The radiator was checked and cleaned but I was told it didn't need it which I can believe from how the inside of the water ports in the block looked.I know I didn't drop any rags or towels in it.The water pump was what failed and it had no cooling issues to that point but I have checked everything I know to check just to eliminate possible causes.I may have the block checked by a machinist for warpage as I had a guy tell me the 4.0 has very little tolerance for it.I'm 99% sure its fine but it is one of the things I'm not postive on and it is an iron block so not sure if thats even true or not.I know when I layed a straight edge on it it looked good to me.

 

[vq5speed]

How fast did it take for the temp to hit 235F. And was this all from just idling.

 

[stx4.0]

it takes about the normal warm up time.once the gauge starts climbing it keeps going until it cant go anymore and it is reading correctly.Mostly just idling but I have put it up close to 1500 RPM while running the heater to see if that did anything.It didn't.I dont run it very long obviously since I don't want to ruin my new heads or crack my block.

 

[murkinstock]

my old thermostat failed and it caused my truck to never really warm up. Even though the water won't stay in the radiator long enough to cool, it also won't stay in the engine long enough to get hot. I would be lucky if it made it to the "O" in normal. Now I have one of those "Fail Safe" ones, and its been working great. The temp gauge sits right in the center.

Now on your issue, I am stumped as well. Have you checked to see how clean the exterior of the radiator is?

When I first got my Explorer it had an overheating issue, so I removed the radiator and sprayed water through it, and I was left with a big pile of sand and dirt.

 

[Centaurious]

Pull the radiator and flush it well. Pull the water pump and see if the timing cover was damaged by the old pumps impeller. Pull the thermostat housing and remove the thermostat, replace the housing. Flush water through the engine from the top and watch for good flow out of the timing cover. If you don't have good flow here your block is plugged.

Overheating is caused by lack of coolant flow or lack of air flow, find the restriction and you find the problem.

Best of Luck

 

[vq5speed]

I seen those Fail Safe thermostats that lock in the open position when you overheat. But how will you know when it locks in the open position

 

[murkinstock]

I seen those Fail Safe thermostats that lock in the open position when you overheat. But how will you know when it locks in the open position

If it gets stuck open, then my truck won't warm up all the way. Since it consistently stays in the middle when warmed up, I'll know after 20 minutes or so of driving and it's still cold.

 

[stx4.0]

Pull the radiator and flush it well. Pull the water pump and see if the timing cover was damaged by the old pumps impeller. Pull the thermostat housing and remove the thermostat, replace the housing. Flush water through the engine from the top and watch for good flow out of the timing cover. If you don't have good flow here your block is plugged.

Overheating is caused by lack of coolant flow or lack of air flow, find the restriction and you find the problem.

Best of Luck

I did have the radiator cleaned from the start.There was no damage to the timing cover,I would have seen that when I put the new pump on.The coolant is flowing in and out of the engine which is making me lean towards there being warpage in the block.I will update if I end up pulling it and having it checked out.