I6 temperature range Normal?

627 Views 19 Replies 11 Participants Last post by turbogus, 16 d ago

MilanR

Discussion Starter · 17 d ago

Quick question for you all. I have a new (to me) ‘76 CJ7 with an inline 6 cylinder motor. It was a restomod so I’m not too sure what the previous shop did. That said, it has a new radiator, new hoses, looks like a new thermostat housing (or at least cleaned up). I don’t know about the thermostat. My question is, is this normal operating range for the I6? The needle stays there and is in the green but seems to be on the hot side. Normal?

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John Strenk

· #2 · 17 d ago (Edited)

I'm going through this right now on my 76.

Read: Winter Warrior

Do you have a shroud on your radiator?
Do you know what temp thermostat they put in your engine?

Here are the specs on the gauge scale:

OEM Temp. Gauge calibration:
Room Temp.....................70 degrees--200 to 400 ohms
C (cold)........................ 130 degrees--73 ohms
Beginning of band........ ..171 degrees--36 ohms
Top of band.................. 242 degrees--13 ohms
H (hot)........................ 270 degrees---9 ohms

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bob4703

· #3 · 17 d ago

That is one reason why I went to an aftermarket gauge that reads in degrees and not C & H. I theory as long as it is in the green you are good. Like you I'd like to see it more in the green for peace of mind.

KDub1984CJ7

· #4 · 17 d ago

Like mentioned in @John Strenk thread linked above, timing could play an issue. I had never considered this, even when my temp ticked up a bit. Mine used to sit dead center between C-H, and about 6-8 months ago I noticed that it had ticked up to about 5/8 up...was winter Temps out...BUT, I had just Nuttered and reset timing as it was retarded by PO.

As @bob4703 stated above, OEM gauge isnt the most accurate but should suffice better than a "check engine soon" light, lol.

MilanR

Discussion Starter · #5 · 17 d ago

John Strenk said:
I'm going through this right now on my 76.

Read: Winter Warrior

Do you have a shroud on your radiator?
Do you know what temp thermostat they put in your engine?

Here are the specs on the gauge scale:

OEM Temp. Gauge calibration:

Room Temp.....................70 degrees--200 to 400 ohms

C (cold)........................ 130 degrees--73 ohms

Beginning of band........ ..171 degrees--36 ohms

Top of band.................. 242 degrees--13 ohms

H (hot)........................ 270 degrees---9 ohms

Thanks for the info! Nope, no shroud. I assume the stock one wouldn't fit the new radiator so they just scrapped it...I may look at picking one up and shaving it down to fit if needed. I assume that will help get the temp down a bit. Regarding the timing, I'm going to leave it alone for now as I need to get it smogged (I missed the cutoff year by 1 in CA) and they may need to adjust it anyway. Photo of the radiator:

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baldfatdad

· #6 · 17 d ago

get a infrared temp gauge from harbor fright. shoot the top radiator hose and see the real temp, then you'll know what the gauge is telling you

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devildog80

· #7 · 17 d ago

I have the same setup in my '81 CJ5 I6 as you do in your pic. No shroud, 4 blade fan, looks like original radiator in mine.....with new cap.

My temp gauge reads where yours is, 114* outside, crawling around on desert trails at 2-4 mph.

I completely agree with baldfatdad, $25 for an IF temp gun at HF, and see what your temp really is in relation to your gauge.

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MilanR

Discussion Starter · #8 · 17 d ago

Thanks guys, will pick up a IR temp gauge. What should it read? Is there any for the hose insulating it? Thanks again for the help.

gehlsurf

· #9 · 17 d ago

MilanR said:
Thanks guys, will pick up a IR temp gauge. What should it read? Is there any for the hose insulating it? Thanks again for the help.

Are you asking if the hoses can be insulated?

I have a whole thread on that. If interested.

gehlsurf

· #10 · 17 d ago

AFR can also play a role- just like timing, one of those things ya don't really think about, but I've seen it with my own eyes while learning tuning with an AFR gauge. It isn't much, but still there. Maybe 5-10°?

It was cool to see, lol. One of those things you read in magazines or see in Hot Rod channels on YT but always seems like a theory. But it's real. Same with Humidity and less Oxygen needing a different tune.

Small things you never notice or see until you get an AFR and actually start to put the pieces together. Anyhow, sorry, kinda went off topic there, lol.

LouC

· #11 · 17 d ago

Later model 4.0s used in Wrangler, Cherokees and Grand Cherokees all run at about 210*F which is the middle of the gauge. I’m not sure what’s yours is running at but I’d guess 220-230*F which is a bit high. I’d think about fitting a shroud if you can. The only time I had higher than 210 as a regular thing on our ‘98 Grand 4.0 was when the original thermostat started getting sticky & wasn’t opening far enough; it was obvious when I tested it, you could test that first.

BagusJeep

· #12 · 17 d ago

Your gauge says you are in the green, that is all you need to know!!!! If it goes up from its normal position, then you need to think.

It looks like a new gauge cluster, so may not be as accurate as the original. (not that it was accurate)

As said, for peace of mind you should measure the water temperature just after the thermostat. You will see the stat opening if you have the radiator cap off as well. There is an opening temperature but full open is a bit higher. This depends to an extent on which thermostat was inserted, should have been a 195 but some mistakenly put in lower rated which leads to increased wear and a cooler heater.

Opens at 195F
Fully open at 218F

You should also have a rad cap rated at 14psi. If any less then you will get boil over at a lower temperature.

Efficiency of the system is affected by radiator cleanliness, coolant, pump etc. This is only a concern if the needle starts to creep upwards and even then only if it hits 250F, the boiling point at 14psi.

For peace of mind I would be concerned if it hit 242F for any length of time, which is supposed to be the top of the green band.

At the top of the band the resistance measured is 13 ohms. You can measure this or replicate it with a suitable resistor, but I just match the readings to what my thermometer tells me.

Bagusjeep got a new engine rebuild, a lot has been renewed. Gauge now goes to 2/3 of Green, approx 220 on the gauge maybe. It measures 205. Happy days if it stays there.

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exheep

· #13 · 16 d ago

I was thinking along the same lines as Bagus regarding the newish looking gauge.
FWIW my 76 gauge reads slightly cooler than that consistently with no shroud or overflow reservoir.

MilanR

Discussion Starter · #14 · 16 d ago

BagusJeep said:
Your gauge says you are in the green, that is all you need to know!!!! If it goes up from its normal position, then you need to think.

It looks like a new gauge cluster, so may not be as accurate as the original. (not that it was accurate)

As said, for peace of mind you should measure the water temperature just after the thermostat. You will see the stat opening if you have the radiator cap off as well. There is an opening temperature but full open is a bit higher. This depends to an extent on which thermostat was inserted, should have been a 195 but some mistakenly put in lower rated which leads to increased wear and a cooler heater.

Opens at 195F
Fully open at 218F

You should also have a rad cap rated at 14psi. If any less then you will get boil over at a lower temperature.

Efficiency of the system is affected by radiator cleanliness, coolant, pump etc. This is only a concern if the needle starts to creep upwards and even then only if it hits 250F, the boiling point at 14psi.

For peace of mind I would be concerned if it hit 242F for any length of time, which is supposed to be the top of the green band.

At the top of the band the resistance measured is 13 ohms. You can measure this or replicate it with a suitable resistor, but I just match the readings to what my thermometer tells me.

Bagusjeep got a new engine rebuild, a lot has been renewed. Gauge now goes to 2/3 of Green, approx 220 on the gauge maybe. It measures 205. Happy days if it stays there.

Thanks Bagus!! Great info and what I wanted to hear!

MilanR

Discussion Starter · #15 · 16 d ago

bob4703 said:
That is one reason why I went to an aftermarket gauge that reads in degrees and not C & H. I theory as long as it is in the green you are good. Like you I'd like to see it more in the green for peace of mind.

ThanIs! What aftermarket gauge did you go with? I’m considering switching for peace of mind/future concerns.

bob4703

· #16 · 16 d ago

MilanR said:
ThanIs! What aftermarket gauge did you go with? I’m considering switching for peace of mind/future concerns.

I was in immediate need of a gauge so I bought what I could find. It is an Equus from O'Reilly's. I replaced my thermostat housing for one for a 4.0 engine. It has a port for the sending unit in the housing. IR heat gun said the gauge was within a degree or two.

devildog80

· #17 · 16 d ago

Within a degree or two at what temp where it shows on your gauge?

bob4703

· #18 · 16 d ago

devildog80 said:
Within a degree or two at what temp where it shows on your gauge?

Thermostat opening at idle.

devildog80

· #19 · 16 d ago

Ok

turbogus

· #20 · 16 d ago

Once you get that hand held temp tool I'd definitely get a shroud on that radiator, IF you can find one.

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