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Unread 01-02-2014, 04:14 PM   #1
Mambo_Dave
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Putting a thermostat in a motor that hasn't had one for a long time - problems?

Hi all,

I found that the Jeep I bought recently hasn't had a thermostat in it this whole time.

I have heard in the past that if a motor runs without one for a long time, that putting one back in can cause problems.

One the other hand, all recent fuel injected motors are made to run at specific temperatures, and running without one means, minimally, running rich.

I wonder if this was, in part, part of the problem with the 4.0L burning so much oil - the motor wasn't coming up to temperature, so the rings probably weren't sealing as well as they could.

I'm just looking to learn here. What are the wives' tales, rumors and provable things you know or have heard about this?

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Unread 01-02-2014, 05:13 PM   #2
rjbruzan
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Put one in. It will take a little time for the computer relearn the paramiters. The engine will run better and more efficently.
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Unread 01-02-2014, 07:00 PM   #3
laybackman
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Install a 195 thermostat. Disco the + battery cable and ground it out for 30 seconds or so. Reconnect it. Now the ECM has no learned values in it. Drive it!
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Unread 01-03-2014, 12:10 AM   #4
Mambo_Dave
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Thanks guys.

Quote:
Originally Posted by laybackman View Post
Install a 195 thermostat. Disco the + battery cable and ground it out for 30 seconds or so. Reconnect it. Now the ECM has no learned values in it. Drive it!
195 installed just before I created the thread.

Interesting. I didn't think about the battery & computer.

But by grounding it out ... just what do you mean?
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Unread 01-03-2014, 03:38 AM   #5
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Easiest way is to disconnect both battery cables, then hold the positive and negative terminals together for 30 seconds.

Ken
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Unread 01-03-2014, 06:44 AM   #6
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Thanks Ken.
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Unread 01-03-2014, 06:49 AM   #7
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Quote:
Originally Posted by Mambo_Dave View Post
Thanks guys.



195 installed just before I created the thread.

Interesting. I didn't think about the battery & computer.

But by grounding it out ... just what do you mean?
You dump the learned memory in the ECM by grounding the + battery cable after it is removed, which discharges the capacitors in the ECM. Now when started, your engine will run on the factory presets. As you drive this YJ for the next few days it reads, stores and averages out all the new input that the ECM receives from the various sensors on the engine. IF anything goes 'out of whack' your CEL will light up telling you the engine is not running within those established parameters when measured against the factory presets

Taking off both cables and grounding them is unnecessary since ground is ground.....no matter where you find it on a vehicle. BUT it is a great time to clean both cables before you put them back on the battery.
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Unread 01-03-2014, 09:56 AM   #8
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Quote:
Originally Posted by Mambo_Dave View Post
Hi all,

I found that the Jeep I bought recently hasn't had a thermostat in it this whole time.
Seeing you are in S. FL I'd say the P.O. had an overheating problem and thought removing the tstat would help.
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Unread 01-03-2014, 02:33 PM   #9
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Originally Posted by atikovi View Post
Seeing you are in S. FL I'd say the P.O. had an overheating problem and thought removing the tstat would help.
I have to wonder. It hasn't been cold as of late (most of my driving it has been during about 80 degree days), and no matter how far or fast I've run the Jeep it hasn't got over something like 140 degrees, so the cooling system doesn't seem 'bad' from what I've seen.

Thus far the things I've found are that the heater core isn't hooked up to the hoses, and the thermostat was taken out of it - perhaps all to just give the riders that much cooler of a ride (less ambient heat from the motor, back, or from the heater core having hot coolant in it).

But, yeah, that would make the most sense - if the YJ had a heating problem.

One thing to always take into consideration is that it was a vehicle from Miami-Dade, and the people down there aren't the most educated lot to be found. They could have taken it out using reasoning none of us would understand, and that science wouldn't support.

But, back to the things that it does do - the already very old hoses are now under more stress since they're beign asked to run at normal temps again. I changed out the upper radiator hose yesterday due to this, and will get to the rest eventually.
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Unread 01-03-2014, 03:27 PM   #10
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Quote:
Originally Posted by Mambo_Dave View Post
I have to wonder. It hasn't been cold as of late (most of my driving it has been during about 80 degree days), and no matter how far or fast I've run the Jeep it hasn't got over something like 140 degrees, so the cooling system doesn't seem 'bad' from what I've seen.

Thus far the things I've found are that the heater core isn't hooked up to the hoses, and the thermostat was taken out of it - perhaps all to just give the riders that much cooler of a ride (less ambient heat from the motor, back, or from the heater core having hot coolant in it).

But, yeah, that would make the most sense - if the YJ had a heating problem.

One thing to always take into consideration is that it was a vehicle from Miami-Dade, and the people down there aren't the most educated lot to be found. They could have taken it out using reasoning none of us would understand, and that science wouldn't support.

But, back to the things that it does do - the already very old hoses are now under more stress since they're beign asked to run at normal temps again. I changed out the upper radiator hose yesterday due to this, and will get to the rest eventually.
Swap out all the coolant hoses...antifreeze/coolant is not cheap and pets will drink the stuff and die...not good.

The heater core could have a leak in it BUT maybe the PO didn't want any ambient heat form the heater core.

One way to find out. Hook it back up and top off the coolant. Rune it until it is hot then check the floorboard on the passenger side of the YJ. See water? Bad heater core.

Make sure the drain for the cabin air inlet in front of the windshield is not clogged up with pine needles etc.

That engine was designed to run at 180F a 195F thermostat accomplishes that. This engine runs it's best ( and cheapest) at that temperature. If it overheats the block water jackets might be be plugged up. But think of that last.


More than likely the radiator is plugged up some.

Radiator check; run it up to temperature then shut it off. Now CAREFULLY feel the radiator core starting at the center which should be hot. Now check the four corners of the radiator. Are they much cooler? Radiator is plugged up.

IF you live in an area that gets real hot (+100F) for days on end you might want to get a duel or even a triple core radiator.

Another issues is the clutch fan.

On a cold engine the fan should spin fairly free. After the engine is running for a while and it gets up to full temperature it should now be much stiffer.

If it isn't then the clutch mechanism should be replaced. Many YJ'ers opt for an electrical fan of some sort.
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Unread 01-03-2014, 03:50 PM   #11
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The problem (or bonus, depending on how one looks at it) is that I work 6 days a week, and that drive is only 3 miles each way.

Eventually I'll have the time to test out the Jeep with the thermostat for a lengthy drive. I'm not opposed to buying a new radiator - it's just something that needs done on old collector-era vehicles. In fact, when I change out the bottom radiator hose it would be the perfect time to put a new radiator in it.

With it running as cool as it did in hot & humid weather, and not really being mudded or rock-crawled, I can't see investing in anything other than a stock type radiator (so I take it that it is a single core?).
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Unread 01-03-2014, 04:31 PM   #12
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Quote:
Originally Posted by Mambo_Dave View Post
The problem (or bonus, depending on how one looks at it) is that I work 6 days a week, and that drive is only 3 miles each way.

Eventually I'll have the time to test out the Jeep with the thermostat for a lengthy drive. I'm not opposed to buying a new radiator - it's just something that needs done on old collector-era vehicles. In fact, when I change out the bottom radiator hose it would be the perfect time to put a new radiator in it.

With it running as cool as it did in hot & humid weather, and not really being mudded or rock-crawled, I can't see investing in anything other than a stock type radiator (so I take it that it is a single core?).
Yes it is a single core unit. Three miles one way? Even with a thermostat this engine would barely go into closed loop mode. I would find a long way home and go that way several times a week. Short trip travelling kills gas mileage, spark plugs, and muffler system/cat converter also. Couple of times a week get it out and up to 50 mph or so for a bit.
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Unread 01-03-2014, 10:44 PM   #13
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Yes it is a single core unit. Three miles one way? Even with a thermostat this engine would barely go into closed loop mode. I would find a long way home and go that way several times a week. Short trip travelling kills gas mileage, spark plugs, and muffler system/cat converter also. Couple of times a week get it out and up to 50 mph or so for a bit.
Well, 50 MPH is easy to do in that three miles. But there really isn't any 'long way home,' either.

It really does get up to the thermostat's 195 with the stop lights and minimal (30 seconds or so) warm up, but I'm sure it isn't a full warm-up.

It is what it is. I work too much, and too hard, to do things otherwise. I'll buy a remanufactured motor for it before I go spending time out driving away from home when trying to get home after the hours I am required to work.
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Unread 01-04-2014, 07:37 AM   #14
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Originally Posted by Mambo_Dave View Post
Well, 50 MPH is easy to do in that three miles. But there really isn't any 'long way home,' either.

It really does get up to the thermostat's 195 with the stop lights and minimal (30 seconds or so) warm up, but I'm sure it isn't a full warm-up.

It is what it is. I work too much, and too hard, to do things otherwise. I'll buy a remanufactured motor for it before I go spending time out driving away from home when trying to get home after the hours I am required to work.
If you are getting up to speed and also sit in traffic that might be just fine.
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