Overheating When Accelerating

[Novarn]

Have a '98 Sport 4.0 SOHC Explorer.

Okay, first for the confession:
Drained and replaced the antifreeze about 9 months ago. Everything seemed fine and then about a week ago my temperature gauge starts going crazy. Pop the hood and find that the reserve reservoir for the coolant is EMPTY. I have since filled the reservoir with antifreeze and continue to drive it to and from work.

This vehicle has been great and I don't do a ton of maintenance on it. I change oil, shocks, and fluids as necessary. Didn't realize that there was a reserve reservoir for the coolant when I changed out the old antifreeze. Yes, I am a bonehead. However, I do need your help.

Now for the problem description:

I do a ton of highway driving to and from work. Whenever I accelerate for a good period of time above a certain RPM (~2500RPM), the temperature gauge goes straight to the top and the "check gauge" light indicates on the dash. However, I back off the accelerator for a few seconds and coast and the temperature gauge returns to normal. I've had to change my driving style to prevent overheating and it is driving me nuts.

What are some things that I can troubleshoot on my own? I'm not crazy with engines, but I can find my way around one if necessary. Since the temperature change seems to be tied directly to the engine revs I was thinking that it could be the water pump. This is just a guess.

Thanks a ton in advance.

 

[exploded99]

Did you pop the radiator cap and make sure the radiator was full? with a leak you will need to be sure all the air is out of the system.

Next, find your leak. Visually examine the bottom of the water pump for coolant, check the bypass hose, etc.

If you've never changed your thermostat, that might be the next thing to try - it may not be fully opening. Its pretty easy to do. Make sure and get a new bypass hose.

General rule of thumb with cooling systems is: Overheating at idle, check the fan clutch. Overheating on the highway, check your radiator.

Thats an 8 year old radiator - your radiator may be clogged up to the point that it cannot be cleaned by flushing - you may have to pull it out and have it disassembled and rodded out.

Its not a 100% guarantee, but if you can idle the truck for a good long while without overheating, the water pump is probably ok. Also, with the engine warmed up fully, pull the rad cap and rev the engine and you will see the coolant moving which means the water pump is circulating it.

Also, time for a new belt?

 

[Papa]

The old standby emergency cooling by turning on the heat works in a pinch. Believe it or not I was in my father in-laws Ford van when it overheated doing 65. Long story short it was the clutch fan. Even the shop he took it to missed it the first time around. I thought I read something a while back about 65k miles being a failure point for a lot of the clutch fans.

 

[gijoecam]

Your thermostat is not opening all the way. It's sticking part-way open. Replace it and all your worries will vanish.

I've had three different vehicles do that to me. Thermostat has always fixed it.



-Joe

 

[psymon]

It is deffinatly the thermostat. I had the exact same thing happen in my 98 SOHC about 6 months ago.

 

[Novarn]

Update

Guys,

Thanks a ton for the advice.

The radiator isn't leaking and is full. I've opened the cap and can see fluid pretty close to the top of the radiator.

Fan belts look fine.

I'll be checking out the thermostat, bypass hose, and clutch fan tomorrow.

 

[roadrunner01]

Try checking the radiator's temperature, when the engine overheats. If the thermostat doesn't open, the radiator will be cool.

 

[aldive]

I too believe that your issues are thermostat related.

Good luck in the resolution ....

 

[pete99ex]

speakin of the devil i had this happen to me at uwharrie which is a trail park in north carolina well needless to say i had no spare thermostat so so i cut the vavle part out of the thermostat and just left the plate with the small hole in it to get me home. it did fine and drove like a champ on the way home so i will be putting in a new one in the next few days.

 

[Doubt Incarnate]

on the topic ot thermostats, where might us sohc guys find a cooler one, like 180 or 160?

 

[Papa]

on the topic ot thermostats, where might us sohc guys find a cooler one, like 180 or 160?

Won’t cooler temps like that throw your emissions and corresponding gas mileage all out of whack?

 

[aldive]

Won’t cooler temps like that throw your emissions and corresponding gas mileage all out of whack?

Yes.

 

[gijoecam]

Won’t cooler temps like that throw your emissions and corresponding gas mileage all out of whack?

Indeed.

However, for a trail fix, 'tis better to run cool than run hot. It's not good, but it's less bad than running hot.

I would not recommend a cooler 'stat for everyday use.

-Joe