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  #1  
Old February 10th, 2018, 19:43
SBpunk SBpunk is offline
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Heating/Cooling Issue

1992 4.0 - rebuilt motor, NEW head, new radiator, water pump, mopar 195 thermostat (pre tested), lower/upper hose, overflow bottle, 50/50 coolant, thermostat housing and it's been professionally 'burped'. Heater vacuum controller (plastic piece of leaking crap) has been replaced with straight hoses to the heater core which has also been back flushed with no leaks. Gauges have been double checked using aftermarket gauges.

Woo ok now that's out of the way. During the colder days my motor will heat up to 210 then drop down to 160 then climb back to 210 then drop a little higher than 160 then back to 210... you get the point right? Anyway eventually it'll settle just under 210 unless I'm running on the highway and it'll climb maybe a bit over. Doesn't sound like a big issue but once it heats up and the A/C starts getting used it'll climb to over heat. This all occurred after my motor was rebuilt. Recently had the head replaced since apparently there was a gap. Didn't change anything but I havent had a chance to test it in warmer climates yet. I've run out of ideas but another forum suggested using a restrictor IE https://www.ebay.com/itm/Allstar-Per...laZqg0&vxp=mtr but figured I'd ask a larger forum in case someone has an idea. Thanks again
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  #2  
Old February 10th, 2018, 20:03
SBpunk SBpunk is offline
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Re: Heating/Cooling Issue

Front and back temp sensors have also been replaced with OE parts from the dealership. All sensors for the matter and have been tested to ensure they're working proper.
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  #3  
Old February 10th, 2018, 20:28
BALTANAKT BALTANAKT is offline
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Re: Heating/Cooling Issue

Having the same issue.

Only I don't get up to 210.

More like up to 198, down to 160, repeat.
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  #4  
Old February 11th, 2018, 03:04
Jim Malcolm Jim Malcolm is offline
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Re: Heating/Cooling Issue

Specs on the rebuild, radiator and water pump? How old is the fan clutch?
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  #5  
Old February 11th, 2018, 05:32
SBpunk SBpunk is offline
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Re: Heating/Cooling Issue

Quote:
Originally Posted by Jim Malcolm View Post
Specs on the rebuild, radiator and water pump? How old is the fan clutch?
Basic rebuild nothing fancy but everything is new and broke in proper. ZJ fan clutch also is new. Water pump is from Napa. Radiator is a 3 row csf aluminum.

Sent from my PH-1 using Tapatalk
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  #6  
Old February 11th, 2018, 06:15
CJR CJR is offline
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Re: Heating/Cooling Issue

A couple of questions:
1. Was the block & head just steam-cleaned and reassembled with new parts?
2. Or was the block & head cooked-out to remove scale &crud?
3. Was the block and head pressure tested for cracks?
4. Was the block resurfaced/decked and was the head resurfaced?

Many years ago, my 88XJ, was running hot when I bought it. I took it back to the dealer,still under warranty, to check it out. The dealer pressure tested it and it tested fine. Later, while driving it down the road on a hot day I saw (in the rear view mirror) a momentary puff of white smoke and then no white smoke. Apparently, the head/gasket would rise periodically and dump hot exhaust gases into the coolant and then the head gasket would reseal. I took it back to the dealer, told them about seeing the periodic white smoke. The dealer pulled the head, resurfaced it, reinstalled the head, and no more running hot issues.

Best regards,

CJR
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  #7  
Old February 11th, 2018, 09:15
SBpunk SBpunk is offline
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Re: Heating/Cooling Issue

It was on all of it. The head was from Clearwater in Florida. The machine shop that did the lower half used new parts for all the moveables. The block was cleaned up, resurfaced, dipped and all that jazz. Least thats what they said. The shop that did it also didn't put the head on correctly and left a gap in the head gasket which is why it had to get redone. Thought the head mightve been warped but never double checked. The block itself wasn't though. The guy that installed the head checked and made sure the pistons looked new. Checked the walls as well just in case. Broken shoulder so I havent been able to do any of the work myself.
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  #8  
Old February 11th, 2018, 11:58
CJR CJR is offline
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Re: Heating/Cooling Issue

When you say "It was on all of it", what does that mean? Specifically, was the block and head pressure tested for cracks? "Dipping" doesn't really remove scale. Blocks and heads typically have to be "cooked" a day or so to get them clean. New heads can be warped. Was the new head from Clearwater,FL checked for flatness or resurfaced again? After engine rebuild and start-up, was the head re-torqued? There are a lot of gaskets sold which state that no re-torque or sealant is necessary. In my view, that's BS. No one can estimate after warm-up, whether the thermal growth in the head bolts will return back to the initial torqued bolt lengths, or what the gasket thickness shrink compression will be, or what will be the loss of head bolt torque that results as the head bolt sealant-coated threads settle in after a warm-up. Re-torquing after warm-up is essential because typically the initial applied torque will be lower. Likewise on new engine rebuilds, everything keeps settling-in for awhile, so another re-torquing of the head bolts always helps. You're done when the head bolts no longer turn. Finally, if a teflon-coated gasket is used between a clean head/block it will eventually tear in shear after enough thermal cycles. The teflon digs into the clean metal pores as the head radially expands with heat and shrinks on cool-down, and the teflon pulls itself apart. Head gaskets need to freely expand and contract radially over the metal surfaces and not be held by the metal surfaces. Solution? Use the old hotrodders trick; coat very clean block/head surfaces with real aluminium paint as used on hot chimneys. Years ago many gaskets were coated this way, because it works. Hope this helps.

Best regards,

CJR
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  #9  
Old February 11th, 2018, 15:21
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Ecomike Ecomike is offline
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Re: Heating/Cooling Issue

I assume it is an HO open cooling system, so replace the radiator cap with a tested, proven to hold 16 psi of pressure cap. rent a pressure tester for that style cap and pressure test the cooling system with the free rental testers the parts stores have. You can also rent a block tester that checks for CO2 exhaust gas in the coolant for peace of mind.

Second, get a new OEM T-stat and replace the T-stat and the Radiator cap at the same time!!! Sounds like the T-stat is bad for sure. IF you can not find an OEM stat buy a Murray T-Stat (Made in Israel, the rest are junk).

Assume the temp cycling has a different cause than the overheating!!!!

Look for reasons why it might be running lean. Inspect the spark plugs for color and other clues as to how the engine is running, like is it running lean, do all 6 plugs look the same!!!!!!!!

Is the Radiator fan cowl still on it???

Is there an exhaust leak blowing on the block or screwing up O2 sensor data.....

Is the AC overheating the system? That is possible!!!!
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