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Overheating...

centex99

Member
Joined
August 10, 2007
Messages
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City, State
Buda, TX
Year, Model & Trim Level
'07 EB
So my 07 4.6L 2wd is overheating... Has 165k miles on it. It seems to be worse after you let it heat up and then drive it a second time... the temp will climb, throwing the fan on, which cools it down, and process continues as the fan puts load on motor and heats it up more, etc...

Isn't leaking fluid. Less than a year ago, overheating issue caused by slow fluid leak was fixed and thermostat and all fluid replaced at that time (precaution). Took it to place who did that work and they diagnosed it as being the fan clutch.
They wanted $500 for the part + an hour labor, I bought it on amazon and did it myself...

However, that wasn't the problem as it's still behaving the same. I have a scan tool, forscan software, etc... Any clues on what I should look at to help further diagnose what the problem might be.
Any other suggestions? I guess I could try to replace the thermostat again, but they often fail open vs closed.
 



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It’s possible to have a bad new thermoset, I have personally experienced it. So you could remove the thermoset all together (not replace) to eliminate that as the issue since you are in the hunting mode. Costs time and a couple of gaskets….

Another possibility is a clogged or blocked radiator. And I have dealt with cars that if you do not ensure you have bleed off all the air out of the system it will ‘air bind’ and thus overheat. But have not had that issue with these 4.6s One option is to – be careful here – start the car from cold with the rad cap off (not the overflow, the actual radiator cap) and look for flow (this is old school). If get a ‘good flow’ you know the rad is not clogged and you do not have air binding… so perhaps do this post pulling the thermostat (does not have to heat up to get flow) and then if flow, cap on, drive (without thermostat) and see if overheats. Blocked rad is look for bent over fins or debris precluding airflow thru it.

Keep at it and post what you end up finding out..
 






So just idling with AC on in driveway... It seems to be operating correctly... it's about 206 on OBD and I'm reading w/ IR 166 on the upper hose and 144 on the lower hose... But also not getting it to easily overheat. fan speed keeps getting adjusted between 450-500 rpm and 800rpm...
 






I would check there is fluid looking in the rad cap opening. If it wasn't burped when the work was done it could be contributing with an air pocket. If you're pulling the thermostat go with a FORD one some parts such as T-stats its not worth the headache in using aftermarket. They are not all the same most OEM's have a pin hole all aftermarket don't but reliability is key.

If you have ramps drive it up and pull the rad cap before it gets too hot and let it run and some air might burp out of it. if the angle is enough.
 






Fluid looks good in the rad cap opening and quite full. I'm not sure what brand t-stat was added. Also, there was a good amount of time in between the work having been done and it starting to overheat, so feel like it isn't likely air. Now, could it be the thermostat restricting flow? possible... I'm considering taking it back to them since I paid a diagnostic fee and having them look at it some more since their suggestion doesn't seem to be the problem.
 






given you know the fan is working which is key under load when cooling of the rad is necessary. The T-stat is #1 in my opinion. I been on a lot of forums for vehicle I own or my son and one thing has become gospel for the older mechanics. Use the OEM's thermostat and not aftermarket. They can fail, hang up etc. Not worth the few dollars saved.

I am not sure about this rad but what I'd done years ago in one of my T-stat repairs to drain fluid for the change is. Get a clear tube maybe 3/8" or so and slide it down into the rad if you can if its a side positioned cap into the rad side ends low enough and you can siphon coolant into a bucket (clean if you're going to reuse it). I don't like using the plastic drain valves too many don't seal when closed or you can't get at them. I always put a coating of silicone sealant on the gasket faces etc before tightening the casting gently (not to crack it). That adds to the sealing of the faces if you can wait for at least an hour or more before filling and using it.

PS: You are lowering the level enough so the top of the block area has not fluid in it.

Hope this works out for you.
Cheers
 






Well, they couldn't reproduce it and get it to overheat like I did yesterday. I think I may just go ahead and replace the thermostat again myself and go from there. I'll use the siphon to pull some fluid out of the radiator, and use a funnel to purge the system, can do this on ramps.
Should I go with stock temp or a cooler temp living in Texas?
 






Stick with the stock temp as the specified Ford part. Otherwise everything can get thrown off creating other problems. Get the write one from a ford dealer for your engine. They can look it up. If the parts guy appears to guess triple check or go somewhere else.

If the shop is willing to work with you on this. Give then the Ford specified stat and let them install it. Then you know where you stand and its eliminated as the fault. They can be intermittent or not fully opening when needed.
 






Well, they drove it one last time and it overheated... doesn't overheat sitting at idle, but driving it, specifically with the AC on, gets it to kick up in temperature after a random amount of time.
 






Yeah, under load which is nothing like idle. Wide open T-stat is necessary for the full cooling flow and one that doesn't stick ever. If it were the rad it would do it all the time. A rad is shot or plugged doesn't alter how it works.. Have them put a certified Ford T-stat in. Bet its all gone afterwards
 






Agree with tripplec do the thermostat with OEM
And if the shop is unwilling, can affirm is the thermostat by removing it and driving it around without one prior to putting new one in. May be a way to make your point with these guys...

also about the bypass, here is what that looks like:
No Hole.jpg
OEM with Hole.jpg
 






Reference ESGWHEEL post above. I have had Jeep Cherokee's, AstroVan 4WD vehicles and in every forum they major DIY long time member alway say USE OEM THEROSTAT only whenever there is a overheating issue when replacing them.

That would be the first thing to do. It also can pass air (burp) through small passages while driving. But a dedicated burping procedure maybe necessary as it depends on the block if these are susceptible to trapping air I can't say due to lack of experience with this block. Others can speak to that but its certainly a major factor in coolant flowing well if enough air it trapped. I would not go for a rad at this point or at least until these have been 300% eliminated as the cause.
 












Well, they replaced the thermostat under warranty since they had replaced it before. This time they went with Napa's "premium" model, which appears to have the bypass hole
https://www.napaonline.com/en/p/THM555090
Regarding the rad cap, I replaced it not that long ago... I think it was OEM, but not 100% sure. I'm going to leave it as is for now, since it should be fixed. In theory the fan clutch may or may not of been going bad... they claim they were able to hold it without it putting up much of a fight, so who knows... but at least I replaced that @ $250 (including the tool) vs paying them the $600 they wanted.
Granted, when I first went in I told them I thought it was the thermostat, but they didn't listen... *shrugs*
I'll leave it as it is, since it should be working fine now... if it overheats again though, I'll be putting on a motorcraft thermostat first thing.
 






Very good


good luck with it.

Fan clutch is very free when its cool or warm as its designed to tighten up when the air get very hot on it engaging the fan to spin even more.
 






Yeah, like I said... was it actually bad? eh... probably not. Does it hurt to be replaced at 165k miles? Not really...
 






They can be quick to take your money!!! The more they replace on your tab the more likely they got the problem covered. Not true trouble shooting but as some of us say, just throwing parts at it since if you do enough parts you'll be right on the money. LOL Not knowing which was the cause.

At least you did not have to do it in the winter. Post back as its good for us/others to know as well.
 






Well, didn't overheat but started idling and then driving like crap after I drove it home (15 minutes)... Bad enough to throw the engine light... Time to read the codes later and see what's next... They didn't mention it doing this while they had it though... It rained today, so perhaps water and coil issues.....
 






Fun... coil #5... also the one closest to the thermostat... it doesn't appear any fluid had leaked into there or any signs of anything... it's also probably one of the coils that have never been replaced. All of the coils seem "loose" though and can wiggle... I have a pack of 8 from autozone so I may just replace all 8 tomorrow. Plan to at least pull that one and see if there's any liquid down there, dry it out, and put a different or at least cleaned up coil on.

I sat and let it idle for quite some time though... radiator hose was hard, so I think the thermostat was opened up... didn't notice any leaks during that time... so hopefully just a replace the coil and it be done type of issue.
 



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Maybe they moved or removed it to work on the T stat. No one well or connected well. Let it all dry and/or get a hair dryer to assist. I keep an old one of my wifes in the garage for cold weather work to warm up frozen items so as not to break them.
 






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