Is it overheating?

My temp gauge doesn't work, so bear with me.
The PO removed the thermostat. I put a 180* one in. I can see the coolant circulating in the top of the radiator, so I know the thermostat and water pump are working, (at least to some degree),and both heater hoses get hot and are filled with coolant, so I appear to have flow through the heater core. Timing is 5* BTDC, but it still boils all the coolant out of the radiator intermittently. It will go three or four days and be just fine, then one day it will overheat and be out of coolant. Is there a way to find out if I just need a new radiator cap? I put a kitchen thermometer on the block when it was hot and it only read about 170*, but that wasn't one of the times it spewed all the coolant out either.
Sound like a cap problem to anyone? Maybe something else?
(no sign of oil or exhaust in coolant, or coolant in oil by the way).

 

I had a similar issue, mine turned to be a belt issue. When it was converted to an alternator the PO used the same belt. When I adjusted the belt it was at full adjustment. It seemed tight enough and didn't squeal so I thought it was OK but the temp would steadily climb until it would belch the coolant. I checked everything including having the radiator flow checked and finally put on a shorter belt and now you can't get it to run hot. The cap can definitely fail but these are low pressure systems ( 6 PSI ) I think so if it is only losing coolant when it overheats it is just doing it's job.

 

overheating occurs while driving the vehicle, can occur while sittng and idling.
Is it really overheating ?
Afterboil occurs after the engine is shut off; the coolant expands and heats up while absorbing heat in the block. This causes the coolant to expand; it can't go anywhere except out the overflow. If you don't have a overflow bottle, then it goes on the ground.

If you are filling the radiator to the very top or just below the cap neck, this expansion will push coolant out.
If you fill about 1" below the cap neck, this will alllow for expansion and most likley not push any out.

Of course, you could check your cap or replace with a higher pressure if necc.

 

I had a similar problem with mine and had the radiator flushed out at a radiator shop. Additionally I drilled a small hole in the thermostat to let air out and the problem went away.

 

For real!? ALL the coolant in the entire system!? If you had a bucket under it, how much coolant are you talking about?

 

1. I have had it occur when idling, and when driving.
2. I know not to fill the radiator to the top and expect it to not spew some out, (learned about that whole thing here actually).
3. It shouldn't build up enough pressure under normal circumstances for afterboil to cause me to loose coolant should it?


Also: when it happens, it is a little over a gallon, (thats what I have to put back in each time anyway). So maybe all thats in the radiator, or less.

I put a new cap on it today, and drove about 15 miles (mostly freeway) and back with no problems, but then again, its not uncommon for it to go a few days between instances.

I will get a new belt when time/money allows as well.

Is there any other way to definitely tell if it is running hot? (besides a gauge that works, I'm working on that). I don't have a good thermometer, (also working on obtaining). Any kind of giveaway with performance or little tricks to help me determine if its too hot or not?

 

Goofy deal. A gallon is a lot, assuming it's not 105° like it is here, and that your brakes aren't dragging, etc, etc. Almost sounds like to me that the thermostat is hanging up occasionally. If it were my prob, I'd pull the thermo, take a screw driver and pry the heat thingy so it was centered, then test a few times in a glass of water at 180-190° to assure proper operation.

 

How did it perform without the thermostat installed?

Run fine, no overheating? you may want to pull the thermostat again.

My Dad had an old Model T back in the late 30's / early 40's that ran fine without the water pump. No overheating, plenty of power and all that stuff. He found a nos water pump for it and put that on. (it originally had a plate bolted in place of the pump) Had nothing but problems . No power, it would overheat in half a mile. Removed the pump and replaced the plate. Back to no problems. Go figure.

 

Thermostat installed backwards?

 

i say a sticking t-stat. buy a new one, 160 or so and drill a very small hole in it to allow it to burp when needed.

 

It was doing the same thing without a thermostat, (thats what led me to get one, figured the one it had was going bad, but there was none).
I wasn't aware of any other way to install a thermostat, (the spring is on the bottom, in the head).
It has been two days without incident.(since I put on a new radiator cap). If I have another problem I will get a new belt and test/drill or replace the thermostat.
Thanks to everyone for your suggestions/help.....hopefully I won't have any more problems....

 

have you done a compression test?

it is possibile that the head gasket is weeeping compression and the conditions have to be just right for it to happen.

 

1. Yes...The compression was between 97 and 110 for all four cylinders, (lost the paper I wrote it down on, wasn't too bad though).....

UPDATE: Third day(today): I take a short trip to the conveniance store, maybe 1/2 mile round trip......get home, park the jeep and it spews all the coolant out of the radiator again, (well, about a gallon again).

Seems that maybe its only doing this on short, non-freeway trips. Not long trips on side roads though.....come to think of it, about a week and a half ago, I was messing with the dwell in the parking lot at work, and after it heated up,and I shut it off and it did this.....

theory: maybe the short/non-freeway trips are getting it hot, but but not hot enough to open the thermostat, (air bubble?), then when I park it, the afterboil pukes all the coolant out. When I drive it for an extended period, or on the freeway though, maybe it gets a chance for the thermostat to open and thus is cool enough to not spew.......
Sound possible to anyone?????

(i tightened the belt today, it was very loose) will vacuum flush the system and inspect/ drill a hole in the thermostat as soon as I can get to the shop.....maybe the alternator bracket, (or lack of one) is the problem.......T.B.C....

 

That would have been nice to know in post #1

 

come on .. be nice.

 

Which part?
I hadn't realized how wobbly the alternator was until recently.....could that be it?

 

I pass

 

could be if it's not keeping enough tension on the belt to keep the pump going fast enough and especially if the fan is not spinning fast enough.

makes some sense since at highway speeds air will flow fast enough through the radiator without the fan and as slow speeds the fan may not pull enough air through the radiator to keep things cool. that might explain why it overheats on local in town runs and not after highway and side roads. (i think that's what you indicated?)

in fact above a certain speed the fan will actually impede the flow of air thus the use of fan clutches or fluid couplings for fans on pre electric fan engines.

 

R)

 

Ok....since operantly I'm being stupid here....I will see what I can do about the alternator, (at least the belt is tight now).....test/drill the thermostat, flush the system, and not waste any more of any ones time.....thanks.