overheating problem

[billydove]

Please help, my 2000 Explorer 4.0 SOHC is overheating. It takes about 20 minutes for the needle to peg H or 10 minutes if the AC is on. It gets hot enough that if I let it go to long it will start boiling out the reservoir. If I turn the heat on, the needle will go to normal and seems to run fine although it seems the trans is seeking in and out of drive and overdrive or bucks at low speeds. Not sure if that is related but it started at the same time. Now that the weather is getting hot, running around with the heater on is getting unbearable.

Ive flushed the radiator with prestone flush and ran it for around 2 hours. Also installed one of those flush kits on one of the heater hoses and ran a garden hose through it with the lower radiator hose off (t-stat removed).

Replaced thermostat and then removed it completely.

Replaced water pump

Pulled radiator when I replaced water pump. Appearance wise it looks great.

Checked the Fan clutch by taking a rolled up magazine and trying to stop the fan. Did not stop. Fan does not turn easily when hot.

Checked for upper and lower collapsed hoses. None found.

When I fill it with 55/50 mix I do so until the it runs out the flush kit fitting on the radiator hose. The T-stat is removed and I get over 2 gallons in it. So I don't think I have air in the system.

No presence of water in oil or any smoke out the tailpipe to indicate a head gasket issue. I bought it new in 2000 and it has always made rattling noise at start up and is kinda noisy when idle compared to other cars Ive owned. Since it has always done this since new and has 95K miles on it. I just chalked it up as being normal since I have never had a lick of trouble out of it until now.

I'm stumped. What should I check now? Should I get a new radiator or pull it and take to a radiator repair shop to be professionally flushed?

Thank You

 

[2000StreetRod]

Good attempts

You have done virtually all of the normal things to identify and correct an overheating problem. I'm guessing from your post that the overheating problem started last winter. You know from the heater valve reducing the overheating that you have coolant flow in the block and your water pump is working. It seems to me that you either have a blockage in the radiator coolant or air flow or your engine is under heavy load. Make sure that there is no radiator airflow restriction (cardboard, dirt, etc.).

Does the engine overheat in Park/Neutral or just when driving? If it overheats in Park and your hoses don't collapse then I suspect your radiator core coolant flow is blocked. When the vehicle is going 25 mph on a level surface and you release the throttle does it slow down much faster than it used to? Are your upshifts delayed like you're pulling a trailer? Did your fuel economy drop significantly when the overheating started? If so, I suspect you have an abnormal load on the engine. That would explain your transmission hunting for the appropriate gear.

 

[McSlug]

Big guess here could be timing although I haven't seen it as a symptom of the timing chain issues that plague the SOHC.

Might be worth investigating the transmission. Usually after you replace everything where you think/hope the trouble is, it ends up being in that other harder place you didn't want it to be.

Try driving with the radiator cap loosened this will stop it over heating as fast. Water boils faster under pressure.
Be very careful not to cook your engine. Cooking your engine will turn it into a boat anchor.
I would not subject your plastic chain guides to any more heat than is necessary either. This will surely hasten their inevitable failure.
I wish you luck in curing your issue.

 

[billydove]

Just wanted to close the loop on the thread.

New radiator resolved the overheating and t-stat is back in. Also no more trans seeking problem so that seems to have been a side affect as well.

Thanks for all the advice