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Old 01-22-2020, 11:29 AM   #1
Gunner41
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3500 overheating

Morning guys this is a long one.

My head hurts because of my 97 3500 7.4. overheating
Lets start with what I did.
Replaced the head gasket. Heads and block were cleaned> Head gasket took the fall.
Replaced water pump, t-stat (195) water temp sensor, water temp switch. New radiator, fan clutch.
Flushed out the water passageways, flushed the oil passage ways.
The engine fired up no problem and no DTC's and purrs but the temp goes up as it sits there and idles.
The only thing that I can find is that the aux fan will not work?
I direct 12 to the motor and it works. I tested power coming out of the connector to the fan. Relay is good. Fuse is good. ( switched both of these.
I turned on the A/C to see if the fan would work but nope.
Im out of Idea's guys and could use some feedback. I want to drive my truck again. Yes the Camrys mileage is great bit its not my truck. Thanks
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Old 01-22-2020, 04:11 PM   #2
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Re: 3500 overheating

Sounds like you might have an air pocket or two in the cooling system.
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Old 01-24-2020, 02:39 AM   #3
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Re: 3500 overheating

You said you tested power to the fans, is there power there when engine is hot? If not check to see if it goes to ground. A lot of vehicle devices are switched to ground not to power. Power would be supplied on the non switched wire. Not really familiar with that truck. If the main fan is engine driven you may want to check out the fan clutch.
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Old 01-24-2020, 10:46 AM   #4
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Re: 3500 overheating

Richard Sir. Good point with the ground. I will dig deeper into it later today. My old fan clutch was good but I replaced it anyway and its good. My aux fan either was (supposed to) come on when the temp sensor kicks it on or I turn the A/C on but It wont. Relays good, fan works in both directions when direct power is applied. I hate to say it but the only thing that I haven't replaced is the actual fan or the heater control.

Last edited by Gunner41; 01-24-2020 at 10:56 AM. Reason: More information
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Old 01-24-2020, 06:53 PM   #5
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Wth?

Apparently you need to understand a couple of things:

Vehicles with both mechanical cooling fans AND electrical cooling fans do not rely on the electrical cooling fans to cool the engine. The electrical cooling fan is for the AC NOT THE ENGINE.
While you probably have an electrical cooling fan problem, this is not the cause of your over heating problem.

We have to assume you did all the stuff you did because of the overheating problem since you put a header of overheating and listed each one of the things you did underneath it.

When you say you are overheating, we are not given any indication of what your are referring to. For example is overheating to you mean the gauge on the dash is going real high? Is the radiator boiling over? Is the coolant being pushed out the overflow tank? Referring to now not before you did all this useless stuff to the vehicle.

When you said in your original post you changed the temp sensor AND the temp switch. Did you mean the 2 temperature sensors that 1. feeds data to the PCM for control and 2. The sensor that feeds data to the gauge?

Does anything change when you drive the vehicle on the highway versus just sitting still?

Have you let the vehicle sit over night to cool and opened the radiator the next morning to see where the coolant level is?

Have you looked to see if there is flow in the radiator after the thermostat opens with the engine running?

One last item. You say you changed the radiator but never mentioned the cap. We sell radiators without caps so my question is are you using the old cap?

Understand the cap is critical to allow pressure to build up in the cooling system. Without this pressure, the boiling point of the coolant is lower than when it's pressurized. A bad cap may not allow enough pressure to build up and can be a cause of overheating.
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Last edited by speedygonzales; 01-25-2020 at 09:04 AM.
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Old 01-26-2020, 08:36 AM   #6
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You neglected to mention some things

I noticed you posted about "water in your oil" back a year ago which you neglected to mention in this post.

http://67-72chevytrucks.com/vboard/s...d.php?t=780040

No posts for a year and then this post.


In your first thread here you mentioned the head and the block were cleaned. You neglected to mention if they were checked for flatness.
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Old 01-27-2020, 12:28 PM   #7
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Re: 3500 overheating

Am I a mechanic? No I am retired Army. Did I spend my life playing with cars and truck? No. Was I forced into this situation because I like my truck? Yes. I'm doing the best with what I have.
Yes the block was checked. Yes the heads were machined. The reason for no post was because I didn't have enough resources to just drop life and fix my truck and I actually hate asking.
Yes new radiator cap.

Last edited by Gunner41; 01-27-2020 at 12:44 PM. Reason: More information
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Old 01-27-2020, 02:38 PM   #8
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Re: 3500 overheating

We are trying to help as well.

I did a head gasket on my 99 back in 2013.

How much coolant/water did you put in the cooling system. How many minutes before it overheats? Does it overheat before the thermostat opens? Does the thermostat open? What head gaskets did you use(big blocks changed through out the years, these are gen 6). Did you take the little shipping caps off the radiator? If you give us more info, we can do a better job of helping.
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Old 01-27-2020, 03:21 PM   #9
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A little testy are we?

If you're going to have an attitude then F you. Figure this out by yourself.

Also I had asked several questions that you never answered. Have fun asshole.
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Old 01-27-2020, 03:23 PM   #10
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Re: 3500 overheating

95 S Trucker. Thank you sir I do realize that and its greatly appreciated. I have only been able to keep this thing going this long because of kindness from you and people like you which is 99.99% of this forum. My problem is when somebody tries to talk down to me for any reason (on purpose) well the fight is on and I will win.
Like I said before anybody can PM me so this stuff is offline. I really do appreciate the help yall have given me bro.
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Old 01-27-2020, 03:25 PM   #11
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Re: 3500 overheating

edited by staff, please use the report a post feature in the future. Thank you

Last edited by Liz; 01-28-2020 at 05:26 PM. Reason: edited by staff
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Old 01-27-2020, 03:51 PM   #12
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Re: 3500 overheating

I'd prefer to talk on the forums, that way it can help someone in the future.
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Old 01-27-2020, 06:36 PM   #13
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Re: 3500 overheating

Yes sir.
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Old 01-28-2020, 07:57 AM   #14
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Re: 3500 overheating

You mentioned changing the waterpump. You may want to check that they gave you a reverse rotation one.
I had my son pick up a pump for his truck several years back and the guy sold him one for a normal rotation pump. He even argued there was no difference in them when I had him take it back.
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Old 01-28-2020, 05:25 PM   #15
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Quote:
Originally Posted by Gunner41 View Post
95 S Trucker. Thank you sir I do realize that and its greatly appreciated. I have only been able to keep this thing going this long because of kindness from you and people like you which is 99.99% of this forum. My problem is when somebody tries to talk down to me for any reason (on purpose) well the fight is on and I will win.
Like I said before anybody can PM me so this stuff is offline. I really do appreciate the help yall have given me bro.
Next time please report posts like that. Its not acceptable

Quote:
Originally Posted by 95 S_Trucker View Post
I'd prefer to talk on the forums, that way it can help someone in the future.
Thank you, taking it to PM will not help the community as a whole. Many folks just dont think of that.
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Old 01-30-2020, 10:05 AM   #16
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Re: 3500 overheating

Quote:
Originally Posted by mingoman View Post
You mentioned changing the waterpump. You may want to check that they gave you a reverse rotation one.
I had my son pick up a pump for his truck several years back and the guy sold him one for a normal rotation pump. He even argued there was no difference in them when I had him take it back.
I was thinking wrong rotation water pump too.
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Old 02-12-2020, 04:01 PM   #17
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Re: 3500 overheating

Thank you all. I found the problem thanks to starting back from basics. It was a twofold issue. 1. The thermostat (while being new) was junk and would not open when I tested it in boiling water. 2. Heater core was blown out but wouldn't leak into the cab. I still have one issue ongoing with my A/C auxiliary fan but the truck wont go past 195-197 so cooling has been resolved (for the most part). Thank everybody for your continued help.
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Old 02-12-2020, 04:51 PM   #18
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Re: 3500 overheating

Here is the diagram for the fan. It will only work when the A/C high pressure side is above 300 PSI or if engine coolant temperature is above 225 degrees.

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Old 03-02-2020, 10:15 AM   #19
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Re: 3500 overheating

Thank you 95 S Trucker. That's perfect. I appreciate all the help.
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