Help me cool down my 383 roadrunner!
#1026746
07/05/11 07:43 PM
07/05/11 07:43 PM
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Joined: Jul 2007
Posts: 291 St. Louis
Imrare
OP
enthusiast
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OP
enthusiast
Joined: Jul 2007
Posts: 291
St. Louis
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I am having an over-heating problem with my 1969, Roadrunner. I have been working half-heartedly at solving this problem over the last three years. Since this car is a trailered show car (driven 60 miles per year) I didn’t put a real high priority on resolving the problem. Plus, if the air temp is 80 degrees or less, there is no problem. The overheating problem only exists when the weather is very hot or when the car is stopped and idling or in a “stop and go” traffic situation where fresh air is not moving through the radiator. Once the car is rolling, even 20 or 30 mph, the engine will start to cool down. Vehicle specifics: stock 1969 383 ci, 4 speed, 22” radiator w/fan shroud, new/tested 190 degree thermostat, new 16lb radiator cap, hood to radiator seal is in place, gravel shield at bottom of front bumper is in place, radiator has been flow tested and validated by Glen-Ray Radiators, Inc., stock OE 7 blade fan and spacer is in place, 50/50 Anti-freeze/water mixture, heater blows hot. I don’t know the exact temperature when the engine is overheating. I am using the OE dash mounted temp gage which simply has a “cold” mark, then what I would call a “normal Operating” mark, to far right of that another mark which would have to be a "do not exceed mark" and at the extreme right is what must be a “ruined” engine mark. The engine generally operates about a needles width to the right of the “normal” operation mark. However, the overheating is real. I have been caught in traffic and had the engine get so hot that it melted the foam firewall steering column gasket, the exhaust heat put a burned spot on the white plastic steering column bearing retainer at the bottom of the steering column, and the engine began to “spark knock”. So the engine is really getting hot, it is not just a bad gage or sending unit that is making me think it is hot. Knowing I was going to ask for professional help I detailed the overheating of the engine on Sunday. The ambient air temperature was 93 degrees, 11:00 am. The engine was started with the radiator cap removed so that I could see coolant flow when the thermostat opened. At no time during the test event can I really say there was positive coolant “flow” through the radiator based on what I saw viewing through the cap opening. After the temp needle pasted the 2nd mark (normal operating) I would periodically rev the engine to see if I could see positive flow through the radiator indicating that the water pump was doing its job. Through the entire test I saw very little, if any, flow through the radiator. I owned an AAR Cuda prior to this roadrunner and I remember viewing the fluid flow in the cuda (340 cid engine, 26” radiator) and the coolant level would drop and the coolant would “rush” to the side of the radiator. That didn’t happen here. However, the coolant would “swirl” a little but I could see bits of dirt in the coolant that just “hovered” round the cap opening. Still, even at 93+ degrees, the engine took 40 minutes from dead cold to reach a point where the engine was clearly getting very hot, temp needle was vertical on the gage in the 12 O’clock position. Just to make sure the same thing would happen with the radiator cap installed, I installed the cap after a short cool down period and the results were the same, taking about 30 minutes to reach the same temp but the engine was started at a higher beginning temp. My suspicion is that there is something restricting the coolant flow through the block, remember, it doesn't overheat if it is moving). I believe some coolant is getting through the block or it would overheat much quicker and it would not run normal temps when moving. I did have the water pump removed during restoration but I don’t remember any problems with it (loose impeller, etc). I did not drive the car in hot weather prior to restoration so I don’t know if the problem existed prior to restoration. At restoration, the recently rebuilt engine was stripped of all paint, disassembled to the short block, regasketed, new freeze plugs installed, and reassembled. The engine runs very good. I need help diagnosing this problem, I'm getting desparate! What should be my next step? Is there a way to effectively “back flush the cooling system that may dislodge debris that could be restricting coolant flow? What would be the best way to check for a blockage in the engine block short of disassembly? Should I remove the water pump and inspect it to look for a loose impeller? Should I remove the engine, remove the freeze plugs, and see if I can find any obstructions (I would really, really hate to do that). Thank you for reading this long manuscript but I felt to properly make suggestions you needed to know the facts and everything I have tired. I will consider each suggestion. Remember though, it doesn't overheat when constantly moving.
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026748
07/05/11 08:25 PM
07/05/11 08:25 PM
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Joined: Aug 2005
Posts: 1,294 Ontario, Canada
FJ5_Fish
pro stock
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pro stock
Joined: Aug 2005
Posts: 1,294
Ontario, Canada
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I would start with a new water pump and a good flushing of the cooling system. Swap to a 180 T-Stat as well. Attach a real temp guage as well and see what the real temp actually is.
Are you loosing water? Any in the oil?
Added: Check the lower rad hose for collapsing as well.
If it has got as hot to melt that stuff, I would also be worried about the engine. It does not take a lot to distort bores and/or to start swapping metal.
Last edited by FJ5_Fish; 07/05/11 10:27 PM.
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026749
07/05/11 10:17 PM
07/05/11 10:17 PM
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Joined: Apr 2010
Posts: 10,570 Sunny South Florida
Golden-Arm
I Live Here
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I Live Here
Joined: Apr 2010
Posts: 10,570
Sunny South Florida
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a good investment would be an infrared temp gun, allowing you to get actual temp reading, by pointing at various locations. it sounds like the block needs to be flushed, and verify the waterpump is the correct one, for the pulley. (or visa versa) the 180 stat sounds like a good idea, and drill a hole or two into the plate on it, maybe 1/8" to allow it to "burp". radiator sounds good, since you had it tested. you might pressure test the cap, just to ensure it's actually working. (new doesnt always mean it works) getting hot enough to melt nearby items sounds like a fuel issue. are you sure the carb is set correctly? float levels okay, seats not leaking, etc? and finally, are you sure fan is sitting properly in the shroud? remove the belt, and spin the fan to check for free operation of the pump. no noises or resistance? just a couple of easy to check ideas. the temp gun, is money well spent, and you'll find tons of places to use it.
"When Tyranny Becomes Law, Rebellion Becomes Duty"
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026750
07/06/11 01:22 AM
07/06/11 01:22 AM
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Joined: Mar 2003
Posts: 4,848 Memphis
HemiRick
master
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master
Joined: Mar 2003
Posts: 4,848
Memphis
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When an engine gets hot it overheats and spews coolant. Has your engine ever done this? If not it's not really overheating. The gauge would also go far to the right if you were really overheating. Your car appears to fail these tests, but this is good.
Take care, Rick 68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026751
07/06/11 02:59 AM
07/06/11 02:59 AM
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Joined: Dec 2005
Posts: 4,299 State of Fascism
52savoy
master
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master
Joined: Dec 2005
Posts: 4,299
State of Fascism
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Like GOLDEN ARM said.. There are so many things to look for. Chrysler did their best to engineer everything to work together. If you've changed one thing that can upset the balance. You should have the correct: water pump pulley diameter crank pulley diameter T-stat or one slightly cooler.. 180. I like 160s clear radiator, head and block passages good water pump. I like the 6 vanes pumps proper ignition timing spark plugs carb jetting/settings heat riser working properly(open all the way when hot) The newer head gaskets have tiny(slotted) cooling holes versus the original gaskets were round. I drill the head gasket holes to 1/2" for more flow.
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Re: Help me cool down my 383 roadrunner!
[Re: Golden-Arm]
#1026752
07/06/11 03:48 AM
07/06/11 03:48 AM
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Joined: Jan 2003
Posts: 21,704 N.E. OHIO, USA
A12
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 21,704
N.E. OHIO, USA
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Quote:
a good investment would be an infrared temp gun, allowing you to get actual temp reading, by pointing at various locations. it sounds like the block needs to be flushed, and verify the waterpump is the correct one, for the pulley. (or visa versa) the 180 stat sounds like a good idea, and drill a hole or two into the plate on it, maybe 1/8" to allow it to "burp". radiator sounds good, since you had it tested. you might pressure test the cap, just to ensure it's actually working. (new doesnt always mean it works)
getting hot enough to melt nearby items sounds like a fuel issue. are you sure the carb is set correctly? float levels okay, seats not leaking, etc? and finally, are you sure fan is sitting properly in the shroud? remove the belt, and spin the fan to check for free operation of the pump. no noises or resistance? just a couple of easy to check ideas. the temp gun, is money well spent, and you'll find tons of places to use it.
on the infared heat gun...sounds just like my '68 road runner a few years ago and then my friend brings out the infared heat gun and points it at the radiator and shows me all of the cold spots and a few warm and hot spots.....60% of the radiator was restricted and not flowing ...and here I thought it was a good radiator that had been "checked" by a radiator shop, replaced the radiator and no more problems. I would heat check the radiator and the block with an infared heat gun as suggested by GA
MikeR
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Re: Help me cool down my 383 roadrunner!
[Re: A12]
#1026753
07/06/11 02:08 PM
07/06/11 02:08 PM
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Joined: Feb 2003
Posts: 10,304 Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
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Posts: 10,304
Someplace you aren't
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Drain some coolant and look down into the radiator. Look to see if gunk has clogged it since the last cleaning/test at the shop. I've had a lot of sand come out of the block and make a home in the cores over the years.
Check your timing and make sure it is where you think it is.
I want my fair share
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026754
07/06/11 03:58 PM
07/06/11 03:58 PM
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Joined: Jan 2003
Posts: 26,538 Rio Linda, CA
John_Kunkel
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Posts: 26,538
Rio Linda, CA
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From the OP I don't see an overheating problem; assuming the factory gauge is accurate, half way up isn't overheating it's just hot. With a 16 psi cap you're good to over 240°F
I wouldn't take any actions other than installing a mechanical gauge to verify the temperatures.
The radiated external heat might be due to something besides the cooling system.
The INTERNET, the MISinformation superhighway
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Re: Help me cool down my 383 roadrunner!
[Re: John_Kunkel]
#1026755
07/06/11 04:20 PM
07/06/11 04:20 PM
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Joined: Jan 2003
Posts: 21,704 N.E. OHIO, USA
A12
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 21,704
N.E. OHIO, USA
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Quote:
From the OP I don't see an overheating problem; assuming the factory gauge is accurate, half way up isn't overheating it's just hot. With a 16 psi cap you're good to over 240°F
I wouldn't take any actions other than installing a mechanical gauge to verify the temperatures.
The radiated external heat might be due to something besides the cooling system.
What if he has the incorrect temp gauge...wasn't there a factory bulletin pointing out the two gauges and one changed the temp range in regards to the needle position back in '68 or '69?
MikeR
Oh and you can put a "catch bottle" on the overflow hose to see if you are losing coolant...
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Re: Help me cool down my 383 roadrunner!
[Re: A12]
#1026756
07/06/11 05:23 PM
07/06/11 05:23 PM
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Joined: Mar 2008
Posts: 571 Western NC
68Bullit
mopar
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mopar
Joined: Mar 2008
Posts: 571
Western NC
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I also agree that he does NOT have an overheating problem. He isn't running hot while moving and only while stopped. Our old cars just run hotter at idle, and during stop and go, and it seems hotter than it is, or could be. I run two gauges. The factory gauge, and an Autometer gauge. I use the second guage to measure against the original gauge just for piece of mind. The Autometer gauge I believe is more accurate, and the original gauge appears to measure higher temps
Last edited by 68Bullit; 07/06/11 05:33 PM.
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026759
07/06/11 10:19 PM
07/06/11 10:19 PM
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Joined: Jan 2003
Posts: 3,905 Minnesota
3twos
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master
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Minnesota
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Did your post say you did not see coolant flow through the radiator? Take the thermostat out and see what happens? Or is the thermostat installed upside down?
Al & Sheila
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Re: Help me cool down my 383 roadrunner!
[Re: 3twos]
#1026760
07/07/11 03:44 PM
07/07/11 03:44 PM
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Joined: Jul 2007
Posts: 291 St. Louis
Imrare
OP
enthusiast
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OP
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Joined: Jul 2007
Posts: 291
St. Louis
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Thank you for all of the good ideas. As far as a different fan or electric fan goes, the roadrunner is restored to OE specs and an electric or aftermarket fan would not be an option. The OE heat gage on my car will go all the way to the right if I let the car get hot enough. For testing purposes, I just let it get real hot then shut if off, that happened to be at the mid point of the gage range. Believe me, I've had it go almost to the 2 O'clock position before. When the car gets really hot it will belch out coolant, believe me, the engine is getting hot, it isn't a gage problem, it does spark knock when hot as well and the engine sits there and creaks in a very un-nerving way as it cools down. Getting a separate temp gage so I know the actual water temp seems like a good idea as well as an infared heat gun. If I find a specific "hot spot" that may help diagnois as well. Loosening the drive belt and spinning the water pump seems like a good idea although it doesn't squeak or leak so I don't expect that will reveal anything amiss. I've checked the lower radiator hose in the past to see if it was colapsing and it wasn't. However, I didn't check that the other day, I will check that next time again. Someone mentioned to do a "flush" of the system which sounds logical. I assume a reverse flush would be what I want to do. The service manual indicates the reverse flush should be done through the lower radiator hose outlet by attaching a speacial tool and forcing water back through the block, radiator, and then I guess out the bottom of the lower radiator hose inlet. That sounds effective, but has anyone seen a sepcial tool (they give a tool number in the service manual) that would seal the lower radiator hose outlet on the engine and allow for the intorduction of water into the cooling system of the engine and back flush it through the block? That I would be interested in. I will work on using these ideas and may be back with some updates. Thanks again for the ideas.
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026764
07/08/11 03:00 PM
07/08/11 03:00 PM
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Joined: Nov 2008
Posts: 1,565 tennessee
pushbutton
pro stock
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pro stock
Joined: Nov 2008
Posts: 1,565
tennessee
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Quote:
DennisH, I agree...It's reached the point I don't need anymore trophy's. But after performing an OE restoration for show purposes, you either have to show them or drive them...you can't do both and be competitive. Now I've reached the point where it time to drive and enjoy (cruises, etc.) but I can't very well do that until I get the over heating issue solved.
Can someone tell me for sure, if the water pump/thermostat, etc is working properly, shouldn't I be able to see a definite "coolant flow" through the radiator cap opening when the thermostate opens?
Thanks,
Yes,you should be able to see some movement. If the rad. isn't stopped up.
Last edited by pushbutton; 07/08/11 03:02 PM.
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Re: Help me cool down my 383 roadrunner!
[Re: Imrare]
#1026765
07/08/11 03:19 PM
07/08/11 03:19 PM
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Joined: Jan 2003
Posts: 2,640 Nashville, TN
MOPARMIKE69
master
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master
Joined: Jan 2003
Posts: 2,640
Nashville, TN
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Quote:
DennisH, I agree...It's reached the point I don't need anymore trophy's. But after performing an OE restoration for show purposes, you either have to show them or drive them...you can't do both and be competitive. Now I've reached the point where it time to drive and enjoy (cruises, etc.) but I can't very well do that until I get the over heating issue solved.
Can someone tell me for sure, if the water pump/thermostat, etc is working properly, shouldn't I be able to see a definite "coolant flow" through the radiator cap opening when the thermostate opens?
Thanks,
Had simular problem. Replaced the stock water pump with a high volume one, removed the thermostat, replaced fan with a thermal unit, then back flushed the system. No more problems. I know people will say you gotta run a thermostat but I haven't for years and it keeps running cool.
69 Road Runner vert 69 GTX hard top 70 Road Runner 4 speed 70 Hemi Cuda vert
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