2.5 lt running cold, need ideas

Hi folks,

I have a temperature related problem, but contrary to the majority of threads I see here, it does not have to do with high temp, it has to do with low temp.

Here is the story:

1984 2.5 lt XJ with 5-speed manual, Weber carb.

Radiator replaced when the truck was bought about a year and a half ago, with a custom 3-row one (we do not have your range of suppliers here, so it had to be made to order, sorry I do not recall what the behaviour was before the radiator change).

The engine is running fine, but the temp gauge never goes above the line to the right of the blue area. Even when going up a hill with first gear! Even in heavy start-and-stop traffic. Even in high-way speed. Nothing I tried can make that needle go above that point.

Attemps to fix it:

- New temp sending unit (no change)
- New temp gauge (no change)
- New thermostat (195 degrees, Mopar unit, like the one before, no change)

The engine seems to be working fine, after running it for a while, the lower hose going to the radiator gets warmed up (which I assume means that the thermostat is opening up and allowing coolant circulation).

Yesterday, I blocked half the radiator with a cardboard, to see if that would make a change. Run the truck around for a while, still the gauge shows low, barely above that first line to the right of the blue area.

Apart from the possible air bulb inside the engine (which I've tried to remove several times), what else could I do to solve the problem? I do not feel good, seeing the temperature so low, since I do not know if I can trust the gauge to show a problem.

All help will be greatly appreciated.

Kind regards

are you getting heat from the heater? if so then you probably have an open wire. if you short the wire the gauge will go full hot,
open full cold. test it, then replace the wire(s) to the gauge.:repair:

After you check the wireing.......

B/C Andy knows what he is talking about. If that does not do it I would check the fan clutch. Mine ran like that a lot. Very cool. And yes its an 84 2.5L.

SV1CEC and I have been through the gauge testing part long ago.

How can the fan clutch make it run too cold? The thermostat should stop flow to the radiator below the rated temperature, in which case it wouldn't matter if the fan clutch works, doesn't work, or isn't even there. In fact, I have a friend (with a 4.0L) who welded his fan clutch solid to avoid constant replacements. His doesn't run too cold.

Mine ran too cold a lot.....

My 84 ran normally in the 180 range. Especially after I put a new T-stat and water pump on. It was just a thought. Maybe even with the T-stat closed it was flowing too much air? Are you sure its runing cool? Have you had the temperature of the engine/radiator check with one of those temperature testers?

Also, did it start this after you put the new radiator on?

Pardon me

You haven't actually said whether this is a heating problem or an indication problem. If your engine is heating properly i.e. the top hose gets too hot to touch when the thermostat opens and it blows plenty of hot air from the heater then lets troubleshoot the indication problem. If the bottom hose only gets warm then that isn't hot enough.

Just for kicks and giggles make sure your thermostat is in correctly with the spring portion in the head. Also I had to change the thermostat twice to get a good one. I found out when I checked it on the stove with a thermometer.

I run an '85 with an aftermarket radiator and it runs relatively cool although the indication is higher than yours. I had to flush out my heater core to get any heat out of it.

If you have already done this then ignore all.

Cool runnings

I took Norbert for a test drive and found that I am reading about what you are. My gauge reads as follows:
100o wide line
blue section
wide line (this is where my needle normally reads)
narrow line
220o wide line
narrow line
wide line
red section
260o wide line

My normal reading is a needle width higher than the wide line above the blue seciton. My heater blows hot and my hoses are hot. I believe this to be normal. I just don't think that this engine runs very hot and has a fairly large radiator. My advice is to consider it normal.

Folks,

Many thanks for all the answers, and I apologize for not coming back sooner, but was away from the PCs all day long.

Here are some answers:

Wires to the gauge and test: If you ground the temp sending unit wire, it deflects fully to the right. Open, it stays on the left (I think, don't remember testing it).

Heat from the heater: One week ago, when I first turn the heater on this year, I hardly got a luckewarm blow. Then over last weekend, I flashed the core and even though it didn't produce that much dirt, now the heater is really heating the truck's interior.

Fun clutch: it appears as if it is fine. You can easily turn it when cold, so I guess it should be OK. Haven't tried to turn it when the engine is hot.

Thermostat is installed correctly, checked with the manuals.

Test engine temp with a tester: I am sorry, I do not have access to one.

Bottom hose gets really hot after the thermostat opens. But even that takes a long time to happen. After I changed my thermostat yesterday, I took it for a spin up on a hill near my house. So after about 10 minutes of climbing up with first gear, I checked the lower pipe and it was hot near the engine but totally cold near the radiator. I drove it quite a bit more, before the lower hose became really hot.

HossHoffer, that's exactly the area that my needle points to also. Mine is a little below or just on the wide line after the blue zone.

What I plan to do for next weekend (if grandma agrees to take care of the twins for a day), is to install a new wire from the temp sending unit to the gauge and see if that helps.

If someone has any more ideas, I am open to suggestions. Neeldess to say, how much I appreciate your input and Eagle's help on this (Eagle is my ... official supplier of XJ parts and my mentor as far as these trucks are converned. So much so, that if I had the money, I would buy a rusted MJ I 've seen in a junk yard, just to make him happy!!! LoL).

Thanks friends and keep those ideas coming.

I'll talk Jeep or Twinn with you any day!

These are mine!

Ghost,

So you know well why my poor XJ has not really been off-road, since it was lifted etc.!!! How old are yours? They look older than mine. I think we need to talk off , I need some consultency!!!

Here are mine.



Couldn't find a Jeep toy to let them play in.

Rgds

10 minutes hill climbing with the lower hose at the radiator not getting hot sounds like a really long time - kind of makes you wonder if the coolant is circulating properly through the engine. Knowing the block temp seems really important here, since if it is a circulation problem, you could be doing serious damage to your engine. It's probably not that, but if I were you I'd want to make sure. Since you say you don't have a temp probe, there are 2 options - most shops/dealers have them and it's the simplest thing in the world to use it, so I'd suggest driving to a shop and asking them to check it free or for $2 or whatever. Second option, even better, some multi-meters have a temp probe circuit. I recently bought one for $15 with the temp circuit, although I haven't used it on the engine yet.

What it should read, I'm not certain, maybe somebody here can verify - but I think the top of the block should read about the same as the temp gauge once everything stabilizes (say after running it 20 minutes). I'll check mine after I drive home from work today and get it warmed up.

Right b4 I snatched my engine It ran like what you describe.....

but it did not have any flow problems that I could determine. As for "burping" the coolant what I do is squeeze the upper radiator hose to make it suck water into it and air out. Works quite well actually. I think the first thing you need to determine is what temperature the engine is running at. I have a meter like this one that I have used when I repaired One Hour Photo Machines for a living. I don't know how much you know about photography but the temperature has to be within 1 deg or your developing process will be slightly off. http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=03482400000 The only thing I have ever done to it wsa replace the fuses. For your purposes it would work fine. These meters will check anything just about. As for the twinns they are 5 and are a challange. Hit me through e-mail [email protected] some time or I also yahoo IM=picturem_99 and AOL IM=pictmanII Check the actuall temperature of your engine first and compare it to the guage. That is what I would do.

Gentlemen,

Here is an update on the above:

I had measured the coolant temperature in the radiator, it is around 80 degrees celcius, or pretty close to what you expect it to be there. I guess that inside the engine it should be around 90-95, which is what you should expect.

It therefore looks as if the problem is an "indication" one and not an operational one.

Apart from :

- new gauge
- new sending unit

I would suspect the wire going from the sending unit to the gauge, so I plan to do some testing with an external wire to see if that corrects the problem.

Anyone can thing of some other part that can produce this behaviour?

Many thanks again and kind regards

Dirty contacts at the back of the guage, will give weak readings. I´ve noticed over the years, the copper contact stripes sometimes grow some oxidation at the contacts (sometimes at the connectors). The amount of voltage/amperage passed by the gauges is, very low, any resistance will show erratic gauge indications.
Most Ohm meters come with a temp. sensor, if not they can be had as a unversal type probe. If your Ohm meter doesn´t have a temp scale, a couple of tick marks with a ink marker, will work as a rough gauge, with a universal temp. probe. You can buy a tube of temp. conducting grease, which when applied to clean metal will give you close to actual temps. A good place to check is the thermostate elbow, bottom radiator outlet area and back of block.
I´ve picked up a few electronic thermos, over the years and have a temp probe for a few ohm meters.
If the thermometer has the range, it´s also good for testing exhaust manifold temps. Wich will tell you quick, if the motor is lean or rich, valve trouble and other things.
An afterthought, I just cleaned the grounds, on my XJ. Especialy the motor to firewall ground, changed the normal indications of most of my gauges a little, but enough to notice.