250 I6 Overheating

['63MurderTruck]

I plan on swapping out my son's 250 for a sbc asap.

In the meantime, I have to keep this I6 on the road for a while.

It's a 250 I6:
It doesn't overheat at idle, it only overheats while driving. This leads me to believe it is a cooling issue and not an air flow issue.

Even though air flow isn't the issue, I'm switching it over to a 3000cfm electric fan.

I've already changed out the thermostat. The old one was a 160, the new one is a 180. This didn't help at all.

While driving the engine heats up to 250 degrees. Obviously, I shut it down as soon as it gets this hot.

There is no leaking of coolant at all. No hoses are collapsing. I've double checked the gauge, it works perfectly.

It has a brand new 3 core radiator.

This is the first time that we've had this motor running, I have no idea of its previous history.

Worse case scenario is a blown head gasket. A buddy told me to take off the radiator cap rev the engine to 2000RPM and watch inside the radiator as the engine heats up and look for 'bubbles'. He said if I see bubbles it has a blown head gasket. No bubbles at all. Anyone else have any methods for checking for a blown head gasket?

I'm aware of a few issues that I plan to work on that may be causing the coolant flow issue:
Timing(if it's a timing issue should I advance or retard the timing?)
Water Pump(any suggestions on how to check this?)
I'm going to flush and burp the system

Are there any other issues that I'm not aware of that may be causing the coolant flow problem?

Thank you

[Isaiah92260]

Originally Posted by '63MurderTruck

I plan on swapping out my son's 250 for a sbc asap.

In the meantime, I have to keep this I6 on the road for a while.

It's a 250 I6:
It doesn't overheat at idle, it only overheats while driving. This leads me to believe it is a cooling issue and not an air flow issue.

Even though air flow isn't the issue, I'm switching it over to a 3000cfm electric fan.

I've already changed out the thermostat. The old one was a 160, the new one is a 180. This didn't help at all.

While driving the engine heats up to 250 degrees. Obviously, I shut it down as soon as it gets this hot.

There is no leaking of coolant at all. No hoses are collapsing. I've double checked the gauge, it works perfectly.

It has a brand new 3 core radiator.

This is the first time that we've had this motor running, I have no idea of its previous history.

Worse case scenario is a blown head gasket. A buddy told me to take off the radiator cap rev the engine to 2000RPM and watch inside the radiator as the engine heats up and look for 'bubbles'. He said if I see bubbles it has a blown head gasket. No bubbles at all. Anyone else have any methods for checking for a blown head gasket?

I'm aware of a few issues that I plan to work on that may be causing the coolant flow issue:
Timing(if it's a timing issue should I advance or retard the timing?)
Water Pump(any suggestions on how to check this?)
I'm going to flush and burp the system

Are there any other issues that I'm not aware of that may be causing the coolant flow problem?

Thank you

One thing for sure, if the head gasket was blown, it would be running like Crap, you would notice besides the over heating that something was wrong.... I have the exact same motor and I've been through a lot with it.... One think I would try Doing is advancing the timing anywhere from 8 BTDC-12BTDC.... Also try burping it. If your truck has a heather, turn the heater on first so that coolant is running through the whole system since your heater core is connected to the water pump.. then burp the bottom hose first then do the top, be carful for bubbles cuz the coolant will be hot. Also since you were asking about the water pump... I'll give you an example of a problem I had. My motor was running warmer than I also felt it should, my whole truck was neglected for years before I owned it... The engine looked terrible, rusty old alternator, water pump, zip ties everywhere, I could tell nothing was ever replaced. So i just started replacing all the accessories on the motor out of good practice and for its own sake. I wouldn't try testing the water pump, you should just replace it if it looks ancient. Mine when I pulled it out, the propellor that pumps the water, was VERY corroded and a couple of the fins almost gone. Once I replaced it with a new one, I could tell a big difference in cooling.

You never know, that could be why yours is over heating because of the pump, I know it made a big difference for me.

[sharkskinman]

What % are u running?
Where are you located?
Is the electric fan in front pushing or behind pulling air thru radiator?
Rotating correct way?
You have electric or mech gauge?
Mech hooked on head above intake between #2-#3?
What's your oil level, temp, pressure looking like?
Does your heater even get hot?

I've got 250..stock fan and an aluminum radiator that is in my opinion too small..my mech gauge runs at about 200 but flexes between 210-215 and 190 normal and 200 highway
33%antifreeze probably but can go low as 10-25% as I'm in new Orleans (not cold)

Overheated once.. Realized PO had taken thermostat out..
Think I've used my electric fan (in front pushing) twice but really didn't need it
That's in town in new Orleans in traffic
And my rings are bad and 2 weeks ago was running on only 5 cylinders..

Ur water pump moving?
Do y you have OG fan as well?

[jdl71]

Making sure the water pump was creating enough flow and/or coolant passages not plugged would seem the most obvious to me as well. Are you getting heat from the heater core?

[padresag]

bottom rad hose collapsing?
ron

[padresag]

what anti freeze mixture are you using? how many lb pressure cap are you using?
what does your guage read to and when it read 250 degrees is it boiling over?
ron

[chevy_mike]

Where is your temp sensor? If in the head, you're likely getting a false reading. I had this issue on my wagon. Moved to port under the t-stat housing and temps were back to normal.

[mehoff400]

Originally Posted by chevy_mike

Where is your temp sensor? If in the head, you're likely getting a false reading. I had this issue on my wagon. Moved to port under the t-stat housing and temps were back to normal.

i am having this current issue. i ordered a new t-stat housing from rock auto for 6 bucks + shipping.

[padresag]

Originally Posted by chevy_mike

Where is your temp sensor? If in the head, you're likely getting a false reading. I had this issue on my wagon. Moved to port under the t-stat housing and temps were back to normal.

I doubt that the change of location would make that much of a difference that he is experiencing. both are factory locations.
ron
also these vehicles did not use sensors but sending units. sensors came in with the use of computer operated systems

[chevy_mike]

Originally Posted by padresag

I doubt that the change of location would make that much of a difference that he is experiencing. both are factory locations.
ron
also these vehicles did not use sensors but sending units. sensors came in with the use of computer operated systems

I saw a 40* difference. I check things with my IR temp probe and even put a thermometer in the neck of the radiator to verify I was not running as hot as it was showing with the sender in the head. It is right next to an exhaust port.

As noted above, it can also be the lower hose collapsing at speed.

BTW, my phone autocorrected sender to sensor.

[padresag]

Originally Posted by chevy_mike

I saw a 40* difference. I check things with my IR temp probe and even put a thermometer in the neck of the radiator to verify I was not running as hot as it was showing with the sender in the head. It is right next to an exhaust port.

As noted above, it can also be the lower hose collapsing at speed.

BTW, my phone autocorrected sender to sensor.

analogue or android phone?
more and more we are being managed by devices that only respond to the current info
these trucks were originally designed with a 7lb cap and a 50/50 ratio water/ethylene glycol mixture to give it a boiling point of 251 degrees and with a 13 lb cap and 50/50 that boiling point goes to 269 degrees as long as the coo;ing system is operating a normally
In actual fact the only time that 160-180 degrees means normal operating temp is when it is running straight water and and no pressure cap as the boiling point of water ie then 212 degrees.
one can run at 230-240 degrees and be within normal operating temps with the right mixture and pressure cap. for every lb of pressure it raises the boiling point 3 degrees. if one is using an idiot light or a dash guage that reads normal nobody is concerned, but if they have a guage that is reading 220/230/240 they get nervous but the above criteria adjusts for that. one just has to remove that 212 degree boiling point from their mind when the system is under pressure and anti freeze.
ron

[Isaiah92260]

[QUOTE=padresag;7565890]analogue or android phone?
more and more we are being managed by devices that only respond to the current info
these trucks were originally designed with a 7lb cap and a 50/50 ratio water/ethylene glycol mixture to give it a boiling point of 251 degrees and with a 13 lb cap and 50/50 that boiling point goes to 269 degrees as long as the coo;ing system is operating a normally
In actual fact the only time that 160-180 degrees means normal operating temp is when it is running straight water and and no pressure cap as the boiling point of water ie then 212 degrees.
one can run at 230-240 degrees and be within normal operating temps with the right mixture and pressure cap. for every lb of pressure it raises the boiling point 3 degrees. if one is using an idiot light or a dash guage that reads normal nobody is concerned, but if they have a guage that is reading 220/230/240 they get nervous but the above criteria adjusts for that. one just has to remove that 212 degree boiling point from their mind when the system is under pressure and anti freeze.
ron[/QUOTE

Very well said! Isn't that also why most cars now in days run hotter? One of the old work trucks I used to ride around in ran at 220 all day and never had a heating issue. Ran great and it was a 1997 GMC.

[vince1]

Like as has been suggested, bottom radiator hose collapsing? If there is no spring in there it will probably collapse. After you stop to look at it all seems normal.

Water pump impeller OK? On another car brand I found the impeller in pieces in the bottom rad hose.

I just remembered to remove the cardboard from the front of the rad and am surprised it didn't over heat.

[sharkskinman]

25/75% anti/water mixture
16lb cap
Small aluminum radiator (1-2pass)
5 leaking rings
Trail of 20/50 oil smoke
Mech gauge at OG temp location on the head
Stock 4 blade metal fan
(Have auxillary fan but never turn it on)

195-200*
Goes up to 230 sometimes but sweeps quickly back to 195*ish
That's in new Orleans and in stopped traffic
Thundering 60-65mph highway still stays about 200*

[vince1]

It's probably not a problem with the Chev I-6 but with the AMC 232/258/4.0L there is the possibility of getting a water pump that turns backwards if the belt set ups are not correct. Serpentine vs V belt and such. And the old plastic impellers break.