• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

I want to shoot my frankenjeep, running cold

W

WarGin

NAXJA Forum User
Location
New Milford CT
Hi guys, I've been messing with my cooling system for over a month now, trying to get my heat to work. The heater core input valve is permanently opened, the entire cooling system was flushed 5 times in the past month. I've replaced upper radiator and heater core hoses, replaced my radiator cap (more on that later) , a new thermostat housing with the sensor port, got an aftermarket MECHANiCAl gauge to try and monitor everything.
My grand accomplishment has been nothing. If anything the heat is colder then the slightly warm air it was before.
84 2.5l with a weber.

Ok , so first off, early XJs have a closed cooling system, with the only opening being the pressure bottle, supposedly. Not on mine.
I have a radiator with a 13psi cap going to an overflow that has a cap that doesn't appear to hold pressure.
Replaced tha cap after the first flush, split upper rad hose, then a week later another heater hose went so I replaced that as well. Burped burped burped burped. Still no heat. Put cardboard in front of the radiator, still no heat.
Flushed burped, burped and flushed some more, nada.

Got a thermostat housing yesterday and hooked it up to a sunpro mechanical temp gauge, and I have discovered that, after running for over an hour in yesterday's snow, in 4wd, with cardboard covering 2/3rds of the radiator, my max temp achieved was 120 degrees. However , as soon as I turned the car off,
The temp would rise to 195 exactly after about 5-10mins. Temps dropped back down to below 100 (not even registering on the gauge) as soon as I fired her up again.

My boss (wheels a YJ) said it could be my water pump not moving enough water?
But wouldn't that make me overheat?
I'm at my wits end, help me avoid losing a toe to frostbite.
 
Are you sure that your thermostat is opening? When the engine has come up to temperature, are the upper and lower radiator hoses and heater hoses hot to the touch?
 
Hoses get warm to the touch. Not to the point that is burns. Definetly not the thermostat, been thru 2 195s, a 180 and a 160. Only just got the gauge but they didnt change the lack of heat
 
What temp thermostat do you have in there now?
 
195 degree.
I can hear the change in idle when the thermostat opens for the first time when warming up, but there really isn't much change in flow once it does.
Is it possible that the impeller on the water pump is so corroded that its not really pushing water more then mixing it around? The coolant system was severly, severely neglected by the previous owner, so I guess that is a possibility.

I'm ordering a water pump cus it's 70 bucks and it can't exactly hurt to replace the 30 year old original
 
Are you sure your heater core isn't clogged to hell?

Its typical for any car/truck to actually heat up after cutting it off because the heat is still there, but the coolant isn't moving....causing a temporary spike in temp. If are only seeing 120deg coolant temp and no heat then you have a problem with a clog or your thermostat is stuck. Try removing it and see what happens. I know its a PITA, but you seem to be running out of options. You could try removing the mechanical fan and seeing what happens, since it is running all the time, it may be a culprit.
 
Well, you've got the correct temp thermostat in there. If the heater and radiator hoses aren't super hot when fully warmed up, and you've tried 4 different thermostats..... what's the temp where you live? If it is the water pump, it should be overheating. If it's a collapsed lower rad hose, it should be over heating. This makes no sense. What kind of fan do you have, solid mount or a clutch type? I'm wondering if maybe your mechanical fan is stuck on, like with a defective clutch. Try what Highspeed said, take off the fan.

Oh, by the way, the rising of temp after shutting off the engine is called heat soak. All vehicles do it.
 
Last edited:
I'm 1000% sure the heater core is not clogged. I've flushed and back flushed it a few times in the past month , first time it was muddy brown, got it clean and it's been clean since. Although I did only flush with garden hose water, no chemicals or whatever.
 
Warlock1 said:
Well, you've got the correct temp thermostat in there. If the heater and radiator hoses aren't super hot when fully warmed up, and you've tried 4 different thermostats..... what's the temp where you live? If it is the water pump, it should be overheating. If it's a collapsed lower rad hose, it should be over heating. This makes no sense. What kind of fan do you have, solid mount or a clutch type? I'm wondering if maybe your mechanical fan is stuck on, like with a defective clutch.

Oh, by the way, the rising of temp after shutting off the engine is called heat soak. All vehicles do it.
Click to expand...

The temp has been fluctuating from teens to twenties around here, but I had the same heat when it's 40. The mechanical fan clutch is stuck on, I have electric fans to replace it but I'm lazy.... But that shouldn't be cooling me 80 degrees below operating temp.
I don't know why but my gut is telling me my water pump is just mixing water around in every direction , not really making any pressure but moving enough to keep from overheating? Or maybe the pump isnt moving the water at all, and my temp guage rising to 120 is just heat soaking?
 
Nothing at all makes any sense on this jeep, It's really getting to me.
I have 2 random belts, a pulley off a dodge, another off a ford, my d30 axle shafts are apparently one offs, and now i can't even MAKE my jeep run HOT!!
 
If your thermostat is stuck open, takes forever for the coolant to heat up to specs, if at all, driving in cold temperatures. The idea from "highspeed" that your heater core may be clogged up makes sense. On the other hand, a lot of stuff is made in china by near, if not by slave labor under red army managers. Hence take one, or all 4 of your thermostats and test them, (one at a time), by using a candy thermometer, a pot of water, and a stove burner. Tie a string, or use a bit of wire in order to dip the thermostat into the water, and when the water heats up as per the candy thermometer indicates to, (near), the indicated temp indented on the thermostat, see if it opens up. If one, or all thermostats check good, then your problem is not the thermostat. However, like russian roulette, you just might have a bummer installed now.., but probably not if all the others check out good. The elimination of the thermostat question will go a long way to solve your issue.
 
Your first issue is to get your thermostat discharge temperature up to 205 or so (thermostat starts to open at 195, fully open by 205, iirc).
You *could* have air stuck in the system, making it act funky. You said you burped it and I believe you. Nevertheless, air can get unbelievably stuck in the system. Try, with the engine off, shaking the upper hose. If you hear gurgling or sloshing, there is air in there.
Insufficient flow from the water pump would make it over heat, not under heat, as we've said.
Do your heater hoses get to the same 120 degrees / warm to the touch as the rest of the motor? I've made goofier mistakes than to think the valve was fully open when it was fully closed.
The fan clutch being stuck on (can you explain this more?) shouldn't be an issue, because the thermostat shouldn't be flowing to the radiator until 195' anyway. The fan clutch would make the thermostat flow less, sure, but only once the engine was up to temperature.
And, I know you've been through a few thermostats -
but if it isn't air trapped in the system causing a bad reading at the temp gauge, I can't think of anything else but a bad thermostat. Overheating can be more complex, but not getting up to operating temperature almost can't be anything else.
 
Not sure if it's relevant but OP has two small holes drilled in the thermostat. One at 6 o clock and one at 12 o clock. It's installed into the thermostat housing the same way. The 12 up and the 6 down.
 
The heater core input valve is permanently opened said:
If your heater core input valve is anything like the one in my 1991, it is quite the convoluted piece of engineering. It's easy to get the input and output hoses confused and the on/off operation also. You say that the hoses get warm. How warm? I would try getting a couple of pieces of pipe and bypass the valve, and have the hoses feed the heater core directly. If you then get some sort of heat, it is either a bad heater control valve (heater core input valve) or it's plumbed up incorrectly. I've been turning wrenches since the late '70s, mostly professionally, and I had to replace mine a couple of years back. I installed it just as the last one came out and it did the same thing. I had to look it up in the factory service manual and it turned out that I had (and the previous owner) installed it incorrectly. It's easy to do.

Also, the stuck fan clutch is not helping things.

And I agree with testing the thermostat. If the thermostat is opening too soon or sticking open, it will cool the system too much and cause the low temps that you are seeing in the cold climate that you are in.
Click to expand...
 
Last edited:
WarGin said:
and my temp guage rising to 120 is just heat soaking?
Click to expand...

No,no. You said that your coolant temp is at max 120 degrees when the vehicle is running and goes up to 195 degrees a couple of minutes after you shut it off. The rise in temp (75 degrees) after you shut it off is called heat soak. This occurs because when it was 120 degrees, the coolant was flowing and getting cooled by the radiator. But when you shut it down, the coolant stops flowing and absorbs the heat from whatever source it is in contact with (such as in the head) without the ability to remove the heat by flowing to the radiator. As a matter of fact, this by itself proves that your water pump and cooling system is working to some degree.
 
Kingkong0192 said:
Not sure if it's relevant but OP has two small holes drilled in the thermostat. One at 6 o clock and one at 12 o clock. It's installed into the thermostat housing the same way. The 12 up and the 6 down.
Click to expand...

This is good. Some people do this trick to try to rid the cooling system of trapped air, as most times the trapped air is usually in the head, as far as I know.
 
Warlock1 said:
This is good. Some people do this trick to try to rid the cooling system of trapped air, as most times the trapped air is usually in the head, as far as I know.
Click to expand...

these are generally referred to as steam holes. but trapped air will not make the engine run cold, it would give you hot-spots usually in the head, but the heater core could be air-bound. but i think the main problem is that you are just simply running too cold. it sounds like a classic case of a t-stat being stuck open, but if you are confident that your t-stat is working i'll take your word for it. i had a 2.5L YJ and it acted similarly in cold weather, but it was a steel bucket so i didnt drive it in the winter anyways.
i think you said you blocked the air flow with cardboard, but if you have time i'd try a run without the mechanical fan. take it right off. obviously take the parts and tools with you to fix it if it gets too hot, but right now you are still in elimination mode.
heres another question, i think i recall this being a new-to-you rig but i'm not sure. was it running ok before? or are you just starting to drive it and you're finding this is another problem?
new water pump is not a bad idea, but it's not likely your problem.
 
How about stepping back and taking a look at the heater valve. They are notorious for crapping out. They are also vacuum controlled. Get the vehicle warm and manually move the little lever on the valve and see if you get any heat.

You may also just have an air bubble in the head screwing with the temp meter. Loosen the sender at the back of the head and add fluid until it comes out that hole.
 
Ok ,
The temp sensor is hooked up to the thermostat housing, not the head . The sensor on the head had 6" of wire going to nothing and I coudnt find an aftermarket mechanical gauge where the sensor would fit that. So there's that.

The hoses get WARM to the touch. Never burning.

The heater control valve was rusted closed, now I have it open full time, capped off the vacuum. I'm reasonably certain that the heater hoses are correctly connected. Maybe I will try to delete the actuator completely.

I will go back to advanced and get 3 more 195 degree thermostats (chances are at least one will work), and a cooking thermometer. If I'm pulling the housing off, again, it's gonna get the best thermostat outta what I got.

The fan clutch has never worked ever since I got the car, the fan spins with the engine at all times, from cold start. Does removing the clutch/fan involve needing to remove any pulleys? Or does it bolt to the shaft sticking off the pulley?

Also one thing I never really understood about removing the head sensor to burp air.
Every time I've tried what everyone does, back up an incline, turn off the car and pull that sensor, air gets pulled in, not expelled. So I stopped trying that.

Thanks for the responses, On my way to advanced now
 
You must log in or register to reply here.

Similar threads

V
High temp woes
2
Replies
21
Views
414
Vitzaa
V
S
Issues flushing dirty coolant
2
Replies
29
Views
4K
fenns7
F
G
Coolant System No Pressure
Replies
9
Views
2K
Woodswanderer
W
8
89 4.0 auto connector question
Replies
1
Views
457
lawsoncl
L
R
Fan not turning on when hot- fan works!
Replies
2
Views
2K
JMA_2001XJ
J
Back
Top