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brand new engine - over heating
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completelyhis
User
May 28, 2007, 8:55 PM
Post #1 of 8
(1315 views)
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brand new engine - over heating
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I put a newly rebuilt engine (2.5L) in my 95 wrangler, new water pump, radiator, thermostat, radiator cap, the whole deal, after running for a couple of minutes, it starts to get quite hot, I shut it down at 210-215, but it shows that it would keep going if I let it.
I rechecked the plug gap, its at .035, I confirmed that the timing is ECM controlled, so it's not advanced, but the top and bottom hose off the radiator are getting hot, though the top seems to be more "radiant" heat than actual water heat. I confirmed the coolant resevoir is at "full." The fan's turning good, good mix of coolant, I just don't know what the problem could be. I have a couple of theories:
1. bad rebuild. Not having enough time, I had a VERY reputable shop do my rebuild for me. Maybe they messed it up?
2. air pockets in the coolant system. I tried driving it around, revving (not above 2,500rpm), thinking it would "burp" any air pockets out. no luck.
any ideas?
Thanks,
Ian
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2007, 5:24 AM
Post #2 of 8
(1313 views)
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Re: brand new engine - over heating
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Air in the system is most likely. You must monitor coolant level at the radiator cap not just the recovery tank. Air in system fools thermostats and sensors and must be removed. Some have a bleeder to let air out usually near thermostat.
You may be ok but need to take some time to get the air out. Start up from cold with radiator full. Feel the upper hose which should stay cold till thermostat opens and warm coolant or hot air is getting out of engine. Then let cool down and check level at radiator again. Fill as needed and repeat. When temp will stay stable drive it around while warmed up doing turns, stops and starts and air will eventually purge out. May take several cycles to get there. Some simply need to bleed out the air as mentioned. Shops don't generally take the time to do this completely and will guess at overfilling reservoir which will eventually stabilize.
A newly rebuilt engine will make more heat but a good cooling system will handle that with no problem.
When all air is out the cooling system should get up to a normal temp and stay there without fluctuating. Some thermostats will have a small notch to let air out when cold and let small amounts of coolant thru to allow for thermostat to get accurate temp info to open and close as needed. Some are so airtight that they are a problem to purge the air out. Either can work, one takes more cycles to stabilize.
Keep coolant at a 50/50 mix and add just 50/50 as needed and I think you'll be ok with this soon,
T
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completelyhis
User
May 29, 2007, 7:36 AM
Post #3 of 8
(1312 views)
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Re: brand new engine - over heating
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Tom,
Thanks for your advice and encouragement! I could not find anything about bleeding the system, so I figured I'd just do as you suggested. Probably ten cycles of starting, watching the level with the radiator cap off, seeing a little air bubble out (just a little), adding coolant, watching the coolant bubble out, and so on...did that about ten times, still having problems. I'm not saying I disagree about it being air, I guess I'm just saying that it seems to be stubborn!
I have three theories:
1. keep trying what you/I described above, hoping it will eventually work out
2. look for a shop that can hook it up to a magic machine that sucks all the air out?
3. run it with the temp sending unit out (only for a couple of minutes, obviously. The temp sending unit is at the upper most end of the thermostat housing, so theoretically, air could escape and the coolant would still flow. it may be a way to bleed the system myself. There are two temp sending units...the one I just mentioned, and one near cylinder 4. Don't know if that matters or not, just thought I'd share :-)
What do you think?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2007, 8:40 AM
Post #4 of 8
(1311 views)
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Re: brand new engine - over heating
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It may not be air at all it's just likely. I have had some so fussy that I jacked up the vehicle at a rediculous angle to make the radiator cap the highest point. If you keep finding it full at cap then we have to rethink what's next. You shouldn't have to remove senders to get air out but it may speed it up,
T
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completelyhis
User
May 29, 2007, 9:43 AM
Post #5 of 8
(1309 views)
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Re: brand new engine - over heating
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Funny you would mention that...my buddy and I actually jacked up the front end substantially, and still didn't get all that much "burp-age." The manual says the operating temp is 205, doesn't take long to get higher than that! Another clue, maybe...the radiator fins never really heat up. I put my hand in front of the radiator, and it is cool to the touch, all the while the the engine is getting hot. hm. seems like the thermostat isn't opening, or staying open. every symptom seems to be indicitave of a stuck thermostat, even though I have a brand new one (actually, second brand new one) in there. air pockets keeping it from opening? water pump not circulating the water (new pump, checked it before put it in)?
Don't know what else it could be.....
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2007, 11:33 AM
Post #6 of 8
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Re: brand new engine - over heating
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Thermostats can be checked visually by putting them in water in a pot on your stove with a thermometer. You can see that it starts to open at the temp marked on it - usually 195F and fully open by 205 or so. Rad should be cold while thermostat is closed and then warm up and notably cool down toward the bottom or return hose. You should be able to feel the warm air from the fan also. If rad is plugged up that's its own issue and new is best of course but flushing it out can help a lot.
A thermostat stuck open will not let the engine warm up and you'll see flow at the radiator when it's cold.
Air is slow to convey temp to thermostat. Ex: 140F air you can stick your hand right in. Don't do it but 140F water will burn you. Higher than that causes severe burns. Again don't try that but you can believe it.
Water pumps about always pump. The failures with them are bearings and leaks. The shaft would have to break for it to stop pumping water,
T
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completelyhis
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May 29, 2007, 11:41 AM
Post #7 of 8
(1307 views)
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Re: brand new engine - over heating
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Rad is brand new, prob not the problem. I think I'll yank the thermostat and run it w/out it, see if the rad gets warm. not a permenant solution, but good for troubleshooting, right?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 29, 2007, 1:57 PM
Post #8 of 8
(1306 views)
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Re: brand new engine - over heating
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Actually not. Better to test that thermostat and put back in. Running without a thermostat can cause overheating unseen in the back of the engine and blow gaskets. You say "what". That's because the restriction it makes allows the water pump to mix all the coolant to the same temp before letting it out to cool at the radiator.
If the temp at the back it way too hot and the front constantly cool the engine is forced to expand at the back and not at the front and it readys cool but is stressing the head gasket. That and temp sensitive engine controls get the wrong message and make improper adjustments.
If you want to try that just for a quick test - OK but don't leave it that way. Easy on gasket cement too. Some folks don't like it at all. I just use the least possible to hold gasket in place and if you use the "form-a-gasket" type you can usually reuse the gasket with just a smear more or nothing at all added.
Sounds silly but make sure the thermostat is in the right direction. The wax pellet -- looks like copper -- and spring end go towards the block/head side and usually have some marking for direction. Some can't be put in backwards, won't fit,
T
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