258 Running too cold - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 05-10-2007, 07:32 PM Thread Starter
Journeyman
 
Tim-E's Avatar
 
Join Date: May 2007
Location: HHI SC
Posts: 117
Thanks: 0
Thanked 0 Times in 0 Posts
 
258 Running too cold

Hola everybody,

I'm not really new to this forum, but my old username didn't work with the new boards...anyway...on to the issue at hand.

I've got an old 258 in my cj-7 that has been running cold lately at cruising speeds(5th gear...60mph) Around town, the engine runs at a normal temp, but on the highway, the temp. gauge is barely over the "C." I replaced the thermostat(OEM spec...195 deg. I think) a few months back and that didn't solve the problem. I replaced the heater core a year or two back...
I think I'm getting worse gas mileage on the highway as a result of this. I think I'm losing as much as 4-5 mpg...and perhaps harming the engine.

The last thermostat I removed was not stuck open...it seemed to be operating fine, the current one is most likely functioning properly.
Any guesses as to what the problem may be?
I can't wait 'til this problem plauged engine blows up so I can stick a new one in there! But for now...I'm working with it.

Thanks,

Tim
Tim-E is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 05-10-2007, 08:07 PM
Keyboard Implanted
 
thorjeep's Avatar
 
Join Date: Jan 2000
Location: In the process of finding it
Posts: 2,561
Thanks: 10
Thanked 1 Time in 1 Post
 
Ok, let me get this straight, on the Highway your engine actually cools down? Are you in a very cold climate? Or are you saying you hit the highway when it is cold, not warmed up yet?

1. Have you put a infrared thermometer to it, after pulling off the highway? They are worth the $40 or so now.

2. Does it cool down after driving it at regular temp?

The gauges are notorious.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
thorjeep is offline  
post #3 of (permalink) Old 05-10-2007, 08:09 PM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,432
Thanks: 1
Thanked 3 Times in 3 Posts
 
Have you checked that pesky fan clutch?
LEVE is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 05-10-2007, 08:51 PM Thread Starter
Journeyman
 
Tim-E's Avatar
 
Join Date: May 2007
Location: HHI SC
Posts: 117
Thanks: 0
Thanked 0 Times in 0 Posts
 
I live in Charleston, SC...wonderfully moderate climate.
The engine(gauge at least) is hot enough when I'm driving locally...but when I get on the highway it cools down...I assume the gauge is working ok...the engine(guage at least) tends to get a bit warm while idling for more than a few minutes. I step on the gas and it cools down.

The fan seems to be acting fine...what would the clutch do to act up?

Tim
Tim-E is offline  
post #5 of (permalink) Old 05-10-2007, 10:07 PM
Keyboard Implanted
 
thorjeep's Avatar
 
Join Date: Jan 2000
Location: In the process of finding it
Posts: 2,561
Thanks: 10
Thanked 1 Time in 1 Post
 
Good Call Leve.

When cold. grab the fan, engine off, and spin by hand. If it doesn't easily. replace the clutch. I just went electric, but that has its concerns too.

What Leve means if your fan clutch engages when cold, it will continue to cool the engine, instead of free spinning. It should only engage when warm.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
thorjeep is offline  
post #6 of (permalink) Old 05-10-2007, 10:43 PM
 
Join Date: Sep 1999
Posts: 5,383
Thanks: 0
Thanked 1 Time in 1 Post
 
That may not be a vaild test this time of year in SC...
Ambiant temp may be enough to partly or fully engauge the clutch.

Anyway, It's not your clutch, it's your sending unit/gauge.
There is only about 30° difference between 'Just Off 'C' and showing fully warm.
Only about 60° difference between needle movment and over heated...

I didn't know this until I put in a mecanical gauge and started watching both of them together.
The factory gauge doesn't budge until about 160° and shows overheated around 210°.

Last edited by Junk Yard Genius; 05-10-2007 at 11:20 PM.
Junk Yard Genius is offline  
post #7 of (permalink) Old 05-11-2007, 12:07 AM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,432
Thanks: 1
Thanked 3 Times in 3 Posts
 
OK Tim... one other thought... I don't know what year you hve for a CJ... but if it's got a CTO switch, that may be failing. Then the ECM never thinks the engine's warmed up and keeps the ECM in open loop.... always runs rich. The switch should trip when the coolant gets to 135*F.
LEVE is offline  
post #8 of (permalink) Old 05-11-2007, 12:39 AM
I Might Just Know What I'm Talking About
 
JeepDawg's Avatar
 
Join Date: Dec 2006
Location: S. CA
Posts: 1,503
Thanks: 0
Thanked 0 Times in 0 Posts
 
I think you could have two problems....

Kudo's to you for making the correlation between temp and MPG.....

You're doing the right things regarding the t-stat....I would have done the same things.....however, I would not be thinking the fan clutch is a problem because the t-stat should still keep the engine at or above 195...

First things first...lets confirm your temp reading is right.....
The sending unit is on the head, drivers side in the rear. Pull it out...hook the signal wire back up...AND connect another wire from engine ground to the body of the sending unit....then get a fresh pot of boiling water and drop the sending unit with the wires attached into that pot. With the ign on, you should read 'around' 212 deg F.

If you do in fact read within 10%, then you are not having delusions....you have a weird problem.....if it's off, swap out the sending unit.

Ok....lets assume that what you are seeing is correct....

With the engine cold, crank it up...keep your hand on the upper radiator hose..and at the same time feel the hose going to the heater....as the engine warms up you will feel the heater hose get hot, BUT, the upper radiator hose stays cold. If the t-stat is working as expected, you will feel it get hot when the temp reaches 195.....in other words, when you feel that slug of hot water go through it..go around and look at your temp gauge...it should be around 195..

It is 'possible' that once the t-stat opens, that it gets stuck until the temp goes way below the 195 temp.....one way to confirm this is to turn on your heater (fun in the summer time) and feel the heat 'before' you get on the fwy...then get on the fwy and when you see the temp on the gauge drop, feel the heat again from your heater...if it's cooler..then once again, it's not your imagination. If thats the case, the only solution is the t-stat.

Now...MPG....I don't think the temp will make 'that' much difference....but the TCO switch could be a factor.....

So...fix the temp reading problem first...then go after the MPG problem.

Let us know what you find.

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
JeepDawg is offline  
post #9 of (permalink) Old 05-11-2007, 01:06 AM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
How's the coolant situation?
If coolant is low, or the system is sucking in air, the the temp sender isn't "wet" - it doesn't "see" the water temp - it can read cold or low.

Many engines get fried for that reason - the operator doesn't get an indication it's hot till it's really hot!
RRich is offline  
post #10 of (permalink) Old 05-11-2007, 03:26 PM Thread Starter
Journeyman
 
Tim-E's Avatar
 
Join Date: May 2007
Location: HHI SC
Posts: 117
Thanks: 0
Thanked 0 Times in 0 Posts
 
Some really good tips up there...I'm sure I'll be able to figure out the problem now.
As far as what year I've got, it is a 1983. No computer controls. Nothing too high-tech under the hood. I don't even want to know what a TCO switch is...

I'm not gonna get to these tests 'til Monday, as today is the last Friday of my college career...So I'm off to the bar! I'll update soon with some results. Great advice.
Thanks, Tim
Tim-E is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome