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Engine over heating and idling problems

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Willie8126 View Drop Down
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    Posted: 25 July 2014 at 7:10pm
OK I got my engine rebuilt and it runs great. My problem is I took it on some rough trails this week and the first day it was over heating. Well in the process of adding water I lost the radiator cap. I bought a new one for the second day. With the new cap I had no over heating problems. I think the spring on the old cap was worn out if that makes a difference. My other problem is when the engine was over heating it idled great, but when the engine was running at 180 on the gauge (I have a 160 thermostat, I think the gauge is off) it wouldn't idle at low speeds which is what I was driving most of the day. Also when I got out on to a paved road and sped up to 45 the temp went up a little. Any ideas.
Thanks for the help
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Old Boy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Old Boy Quote  Post ReplyReply Direct Link To This Post Posted: 25 July 2014 at 8:51pm
Hi, you cannot base the engine temperature gauge accuracy based on the stat opening temperature. The 160F is only the temperature the stat will be fully open at. It is down to the cooling system to them keep the engine temperature within limits. As for your poor running I suggest a tune up. Check fuel mixture, carb jets, ignition timing, points gaps, plugs etc etc. Smile
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Willie8126 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Willie8126 Quote  Post ReplyReply Direct Link To This Post Posted: 25 July 2014 at 9:25pm
Everything was replaced last year before Ihad the eengine rebuilt. The reason I think the gauge is off is if you check the water temp with a thermometer it is less then what the gauge says.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2014 at 5:55am
A radiator cap doesn't make and engine run cooler, it only raises the temp at which the coolant will boil. I think the original caps were 7 psi and the water pump seal won't hold much more than that. I think your overheating problem is a stopped up radiator.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scoutpilot Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2014 at 10:24am
We're missing a lot of details here. 
How many miles/hours since rebuild? 
Was the radiator boiled out/rodded/cleaned/recored or just flushed? 
What was psi for lost cap? 
What is psi for replacement?

For the carburetor. You indicate it was a rough ride. By chance could the float have been knocked about and jammed up? Could you have dislodged some crud in the tank and it found its way to the carb? Got a filter? 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote damar2yxr Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2014 at 1:01pm
X2 with Carl and Rick. That radiator question needs to be answered. Your problem was similar to mine and fixed with a recore.Big smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oilleaker1 Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2014 at 2:04pm
Old original radiator caps did not have a rubber seal on the bottom. They were brass and sealed on a gasket that was in the radiator neck. New ones have it. The pressure should be 4 pounds. Unless you have a water pump bypass hose, the thermostat needs a small bypass hole or you'll have initial overheating problems.  The list is endless on idling problems, and what to do to counter overheating. Read all the threads you can about this with a search and then apply that knowledge to your situation. You will need to take notes and make a list of things to check off, one by one until you find the problem. John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lee MN Quote  Post ReplyReply Direct Link To This Post Posted: 27 July 2014 at 2:47pm
MHO, and I agree with all comments posted here but will add, your waterpump temp will be 20-30 degrees cooler than the head temp as it is running in coolant that has passed through the radiator. I have spent much time with a temp gage checking 134 engine temps, the hottest part of the head is at cyl. no 3, and that's where the gage gets it's readings. Your old cap, if it did not have a gasket would piss coolant till it was low enough not to, and may have given you the impression that it was overheating but was not.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Willie8126 Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 12:56pm
I've got about 100 miles on the rebuild.

The radiator was just flushed out. It leaks a little from the core near the top and I need to either get it recored or a new one.
The old cap was 12lbs and the new one I put on is also a 12lb cap.
I have a hole in the thermostat and I have a hose that runs from the water pump to the back of the block I don't know if that is the bypass mentioned above by Oilleaker1 or something else.

Its idling fine again so I don't know if it had junk in the line or something else.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 1:25pm
The cap pressure is too high, 4 1/2 lbs is factory recommendation. A hose going from the water pump to the rear of the block sounds like there was at one time a heater connected and now the two connections are simply being tied together.



Larry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote damar2yxr Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 4:28pm
When a radiator works properly there is fluid traveling down all the tubes with no interference to flow. You can still appear to have a circuitous flow when the thermostat is open and it looks like the coolant is flowing well but you could have many of the tubes clogged with sediment and not even know it. A partial clog will easily cause overheating. I bet with a new core you won't be overheating.Big smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 4:55pm
Rereading this I don't see anything that actually indicates it's overheating, in fact you indicated in the first post that the problem was solved. Is it? Remember, when filling the radiator there should only be enough coolant to just cover the tops of the tubes. If you fill the tank itself there's no room for expansion and it will push the excess out the overflow, moreso if the cap's bad. Running at 180 on the gauge with a 160 thermo is not an indication of overheating. If I read the additional posts you've made it's now running and idling OK also so, everything's OK?

Larry


Edited by rocketeer - 29 July 2014 at 4:59pm
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Willie8126 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Willie8126 Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 6:19pm
It was over heating then I put the new cap on. After I put the new cap on it didn't over heat at the slow speeds but still warmed up at the higher speeds. I was wondering if that was normal.

I'll change out the cap for a 4 1/2 lb one. I went with the 12 lb because that's what the only one was.

It does idle better now but I haven't driven it much after getting back home.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 10:55pm
If you can find a 4 lb radiator cap tell me where you got it. I have not found one anywhere. The only place you MAY find one is NOS. That is the reason I leave my radiator cap loose because I could only find a 7 lb cap. When I lock the cap down the water pump leaks the coolant and then the engine overheats. 

DO NOT fill more than 1/2" over the top of the radiator cores. It WILL purge anymore over that.

If your radiator is leaking at the cores you need to replace it. Check the core replacement price and the radiator replacement price to see which way to go. 


Edited by Carlsjeep - 29 July 2014 at 10:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Old Boy Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 10:58pm
Try Universal Jeep Supplies in the UK for any part common to both MB/GPW and the CJ-2A. Cliff Harris and the team are excellent! Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Willy Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 11:02pm
Carl, per their web site Kaiser Willies has 4 lb caps for both bottom mount and side mount radiators. Did not research other than reading 4 lb cap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2014 at 11:49pm
Walcks has them too, really not that difficult to find.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Willie8126 Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2014 at 1:21am
OK just so I'm straight. Should I replace my 12lb cap with a 4 or 7lb one.
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