Ryno_yj Posted November 22, 2012 Share Posted November 22, 2012 I was out messing with my Comanche today after eating dinner and the temperature gauge pegged to hot. It has two electric fans that were both running. The weird thing is, the radiator was really not even warm. Could this be a thermostat not opening? The engine was very hot so I am sure it wasn't just the gauge messing up. Thanks for any help you can give and Happy Thanksgiving. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted November 22, 2012 Share Posted November 22, 2012 Assuming your coolant level is good, you could have a multitude of issues. Plugged radiator won't let coolant flow, T-stat won't open, plugged water jacket in block, water pump fins have corroded away. The last one is highly unlikely, but still possible. I would start with a good flush and check to see if the T-stat is working. Put it in a pot of boiling water. Also check to see if the front of the radiator is blocked with depris, leafs, grass, etc. . . Link to comment Share on other sites More sharing options...
Eagle Posted November 23, 2012 Share Posted November 23, 2012 Plugged radiator. Link to comment Share on other sites More sharing options...
NotMatt Posted November 23, 2012 Share Posted November 23, 2012 How much air do your two electric fans pull CFM-wise? Also, how hot is "very hot"? Link to comment Share on other sites More sharing options...
Ryno_yj Posted November 23, 2012 Author Share Posted November 23, 2012 Sorry fellas for being kind of vague. It appears that the PO actually did the conversion to the newer style cooling system. I did not even pay attention to the radiator cap sitting there on the radiator and the lack of a pressure bottle. The radiator also looks basically brand new so would not think it is plugged, of course I know weirder things can and often do happen. As far as hot, the temp gauge was pegged at 250 degrees. The engine was definitely hotter than a normal operating temp. Unfortunately I did not get to check the coolant level because I was waiting for it to cool off but ran out of time and had to come in to work. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted November 23, 2012 Share Posted November 23, 2012 Check coolant level and pressure cap. Link to comment Share on other sites More sharing options...
Eagle Posted November 23, 2012 Share Posted November 23, 2012 Could this be a thermostat not opening? Yes, it could. There is one other, oddball possibility. If the PO replaced the water pump, he could have gotten one for a 4.2L engine with vee belts rather than a serpentine belt. Externally they look alike and they both bolt to both blocks, but the direction of rotation is reversed for the serpentine belt, so the impeller vanes go the other way. Link to comment Share on other sites More sharing options...
Ryno_yj Posted November 23, 2012 Author Share Posted November 23, 2012 Well I took the tstat out today and took it up on the hill after topping off the coolant. Everything seemed fine, the temp went a little over 210 but not very far. I then took it down to my parents hay field and ran it pretty hard doing some donuts and stuff, purposely trying to raise the temp. Well, it worked and the gauge spiked to 250. I immediately stopped and shut the engine off. I let it sit for about 15 minutes and turned the key to on. Oddly enough, the gauge spiked back to 250. So I started it up and it almost immediately dropped back down to 210. I went back to the house and let it sit and run and it started creeping back up to 250. I let it keep running to see if there was any coolant being spit out. There wasn't a drop coming out. If that thing was really that hot shouldn't it be spitting coolant? Also one time my buddy's cherokee got hot bc of a stuck thermostat and it started knocking and sounded awful. My motor doesn't make a weird noise at all. What I am getting at is, could it be possible that the gauge is more at fault here than actual heat? These are aftermarket auto meter gauges and the oil pressure and fuel gauges also act weird. Link to comment Share on other sites More sharing options...
87MJTIM Posted November 24, 2012 Share Posted November 24, 2012 If I am reading your issues correctly, the temp only rises when the truck is not moving. When you are driving it, the temp is normal. I had a similar problem and it was the water pump. As the truck was moving the coolant moved thru the engine because of the cooling air flow. No air flow = no coolant flow = over heat. Link to comment Share on other sites More sharing options...
Eagle Posted November 24, 2012 Share Posted November 24, 2012 If I am reading your issues correctly, the temp only rises when the truck is not moving. When you are driving it, the temp is normal. I had a similar problem and it was the water pump. As the truck was moving the coolant moved thru the engine because of the cooling air flow. No air flow = no coolant flow = over heat. See post #7. It's an outside possibility, but it is a possibility. With a new radiator and no thermostat, the temperature should not get anywhere near 210, let alone 250. Remember, the purpose of a thermostat in an automobile engine is to keep the temperature UP, not down. Run it again until it's hot, and check the radiator to see if it feels hot. Link to comment Share on other sites More sharing options...
Ryno_yj Posted November 25, 2012 Author Share Posted November 25, 2012 If I am reading your issues correctly, the temp only rises when the truck is not moving. When you are driving it, the temp is normal. I had a similar problem and it was the water pump. As the truck was moving the coolant moved thru the engine because of the cooling air flow. No air flow = no coolant flow = over heat. Actually after tinkering some more with it today I have found it to be the total opposite. It will hover at 210 all day long at idle, but as soon as I start driving it and put a load on the engine the temp starts to rise. Then it has to sit for quite awhile to cool off after shutting it down. I also ruled out the temp sending unit today because I ran it enough to actually get the coolant to boil over in to the over flow tank. This is when I noticed some light brown coloring in the lower part of the over flow. My instant thought is oil in the coolant, which means a blown head gasket. I checked the oil and it is nice and brown with no milky color or foam at all. A good friend of mine came and picked it up today. He has some sort of chemical tester that detects combustibles in the coolant and he is also going to do a pressure test. Hopefully whether it is good or bad news I will have something to go on. Link to comment Share on other sites More sharing options...
jeepsouth Posted November 25, 2012 Share Posted November 25, 2012 Wish you luck man my son's 2000 ford ranger 2.5 just blew the head gasket for the second time. He scrapped it. Third vehicle i've bought for him ,and the last. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted November 25, 2012 Share Posted November 25, 2012 Actually after tinkering some more with it today I have found it to be the total opposite. It will hover at 210 all day long at idle, but as soon as I start driving it and put a load on the engine the temp starts to rise. Then it has to sit for quite awhile to cool off after shutting it down. I also ruled out the temp sending unit today because I ran it enough to actually get the coolant to boil over in to the over flow tank. This is when I noticed some light brown coloring in the lower part of the over flow. My instant thought is oil in the coolant, which means a blown head gasket. I checked the oil and it is nice and brown with no milky color or foam at all. A good friend of mine came and picked it up today. He has some sort of chemical tester that detects combustibles in the coolant and he is also going to do a pressure test. Hopefully whether it is good or bad news I will have something to go on. Chemical/Pressure whatever you fancy test the pressure in the cylinders Answer: Head Gasket Link to comment Share on other sites More sharing options...
NotMatt Posted November 26, 2012 Share Posted November 26, 2012 It'll be interesting to see what the coolant pressure test and contaminant test comes back with, but I'm still wondering what kind of fans are installed, since you said "two electric fans"... A lot of people think you can just slap an electric fan on in place of the mechanical one and it will cool just as good or better than the mechanical fan, which is not necessarily the case. All electric fan setups have their place, but the setup needs to be well-designed to work with the system and keep things cool. A 50 dollar parts store curved blade fan that only pulls 700 cfm slapped on in place of the stock mechanical fan is going to make things worse, not better. So, before you go concluding that your rig needs a head gasket, you need to make sure you're actually pulling enough air through that radiator to cool off your motor, especially since you didn't install the fan, the previous owner did. Link to comment Share on other sites More sharing options...
relyt120 Posted November 26, 2012 Share Posted November 26, 2012 Be wary if that test turns up negative for a blown head gasket, used one on my mom's xj and it turned up negative. Issues persisted so we went ahead and changed it. Made all the worlds difference. Link to comment Share on other sites More sharing options...
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