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I've got a '74 Challenger with a 383 (the 318 it was born with is somewhere in the ether) and I can't seem to find why it's overheating. I've replaced the entire cooling system with new Cold Case radiator, new hoses, new 180 degree thermostat (I tested to ensure it does open), new water pump, two electric pusher fans and two electric puller fans. I do have a Sniper EFI instead of a carb on the engine and the water pump is electric (50 gpm). I am not intending to nor have I ever drag raced it. Maybe someone before I owned it did... no clue. I make that point as folks that know more than me mentioned the reason for an electric water pump suggests maybe the car was drag raced. I do get really good temperature data from the Sniper and verified with an IR thermometer. The car, in any temperature, steadily climbs to 220 after a few miles at which point I shut it down and let it cool off before running it back home. I put a part in the upper radiator hose from Champion that has a screen filter with a glass body https://www.championradiators.com/ra...t-filter-black which allows me to verify the coolant is, in fact, flowing. I am stumped on what to look for next. Any thoughts?
Thanks & FYI this is my first restoration attempt and while I've learned a ton I am admittedly a complete amateur at this stuff.
How large of a radiator did you install? How Many Rows?
Also, Have you tried using "Water Wetter" in the system?
And is the thermostat staying closed long enough for the radiator and fans to cool the water within the radiator?
Just a Question for you or the group...... How many GPM dose a stock belt driven water pump put out or move?
After 40 years here I am so ready! My wife has 2 years & 7 months until she retires and I work remotely so my plan is living anywhere else that is 25 degrees or more cooler from May/June until Halloween.
As far as the thermostat once it goes above 180 degrees I don't see the temp come down at all while driving or at idle unless I turn the heat on and even that doesn't bring it back to near 180. I do have heat btw so appears the heater core is functioning properly.
2 row in your climate is questionable. The fact that it comes down with the heater on shows it can cool, but it's not getting enough from the radiator. Do a quick test to make sure you're not getting cylinder air in the coolant either through a head gasket leak or cracked head. Remove the fan belt on the water pump. Pull out the thermostat with coolant right up to the base of the thermostat housing. Start it up. If you see bubbling, there you go, you found a leak. The coolant will rise or spill over a bit as it heats and naturally expands. What you're looking for is bubbling. Exhaust sniffer in the radiator too while fully assembled works too.
We did this on my buddy's 383 Charger that ran warm like yours. Drained out the coolant, block and all. Filled with distilled water so no rusting. Added Dominator coolant boost from Amsoil. This stuff works much better lowering temps up to 20 degrees in some cases if used with distilled water. If it works you know you have engine heat that isn't getting removed by your radiator.
Thinking more on your warm engine. Did you have over heating issues prior to installing the electric water pump? 50GPM is a lot. I'd say too much. The coolant needs to be exposed to the radiator long enough to cool down. Speeding through the radiator may sound good but it's not. If it zips through in seconds it will never be exposed long enough for the fins to cool it. I've seen this with people who changed out pulleys making the water rush through the radiator and developing a heat problem.
I've spent the majority of the last 3 years on rustoration work and just recently began looking at issues with the drive train. The water pump is inherited so I just checked what it is rated for and it shows 50 gpm. I am planning on looking at the timing first and then going through (step by step) with suggestions you all are offering in the thread. I want to jump right in but it's ungodly hot here right now and I am juggling a bunch of stuff at the moment. Might be a bit until I dig in but I promise to come back and update ya'll on my findings. I am so appreciative of your help. Learning a ton of stuff I wish I had learned in my youth.
Is the pump is flowing in the correct direction, is it wired correctly?
I don’t like that it’s overheating under all circumstances I would be looking for compression in the coolant. You don’t mention what heads are on the motor but a head gasket failure is very possible. I’ve seen enough edelbrock head failures to warrant the need for checking into them, same with old cast iron.
Water pump is going in correct direction. I tested before install so I can rule that out. As far as a bad head gasket would I see the oil or coolant getting fouled? I don't know what heads are on it.
My concern with that water pump pushing out 50 GPM is that it has the potential to suck the suction hose closed making it collapse. I've seen that happen with stock pumps with weak hoses never mind one like yours.
You should let the engine heat up with the cap off the radiator, it will dump coolant as it expands, refill it after it cools down, but what you want to see is if there are bubbles. That would be a heat gasket.
I'm still stuck on the temperature... 180* thermostat and moving up to 220 is only a 40* difference for an area that runs between 100* - 125* ambient temperature....
Mostly dry heat ...... Some humidity sometimes, when it rains.....
With That said..... Lets look at the basic flow rate of a stock water pump...... ( You guys can grill me as you wish!!! )
Basic cruise speed GPM is roughly 30 GPM...... Basic idling speed GPM is roughly 10-15 GPM
SOooooooooo
My thought is that a Restrictor may need to put in place to adequate slow that water flow so it has time to cool and heat when it cycles through the cooling system..
My second thought is that the capacity of the radiator in just not large enough for those types of temperatures for adequate cooling.
Most of the folks that i know that I have helped in your area, have belt driven water systems.... And they at times do run hot, but not overheated... They do also run a single pusher fan, a larger radiator, and also water wetter in the systems....
I agree on radiator capacity. It was always an issue with Mopars back then. The large capacity radiators with 3 rows never were in the shop with chronic overheating problems, unless they rusted. Once rusted things got very plugged up. My 3 row radiator in my 383 Dart in Massachusetts never runs hot. We're experiencing temps in the upper 90s now and it still only budges the needle to the first normal mark. If we lived closer, I'd do a radiator swap for a day and see what happens.
07-24-2023, 02:09 PM
