Cooling Issue

[cuda2002]

I have a 73 'Cuda with a 383, mild cam and headers.  I installed a FAST EFI kit last year. I have had cooling issues over the years and decided to do something about it.  The cooling issue pre dates the EFI conversion.  The car was working well while driving but in traffic the temp would creep up to about 210-220 and want to keep climbing.  It would go back to about 190-195 F when I would start moving.  I have a 22" 3 row rad. It was re-cored before I put it in.  I have a B&M tran cooler attached to the front of the rad. 

 I know that the issue is either not getting enough air past the rad or water pump/thermostat.  Since I didn't have a shroud, I got one and installed it.  Made little or no difference.  Belts don't slip, fan is turning in the right direction, right size, number of blades as far as I can tell.  So I turned my attention to the thermostat and water pump.  I recently purchased and installed a Milodon High Vol Pump with a Mr Gasket 180 F High Performance Thermostat. The thermostat that was in the car was a regular 180F one.

First go with the changes, the car started to overheat while driving so I took thermostat out, and ran without. Water pump works.  Put thermostat in a pot of boiling water, it didn't open.  So Ahha, bad brand new thermostat.

Shop only had Mr Gasket so had to get another one.  I tested this one before I installed it.  It opened at the right temperature.

Put new thermostat in took the car for a rip, all looked good.  Drove around for about 20 min, temperature was in the 190 range when driving looked like in traffic that temperature was looking good.  Went up slightly but not nearly as fast as before. PArked the car for 1/2 hr and went to take the misses for a cruise and didn't get around the block before the temperature started to rocket up while driving. 

Thought ok, maybe a vapour space in the system.  Disconnected heater hose and added some coolant.  Ran car until it started warming up, no rad cap, as I wanted to see the thermostat open and coolant flowing.  Nothing.

I had my laser pyrometers checking temp, everything was looking good but temp gauge and my EFI data both show temp about 30F hotter than what I am measuring with my pyrometers.  Figure ok, keep going pyrometers should be correct.  Pyrometers should read a little low with heat transfer through the metal but not 40-50 F. No!! Sure enough when my pyrometers was reading 175F gauges were getting over 220F I got a geyser. No flow across the top of the radiator before this happend.

What am I doing wrong with the thermostat installation?  How likely is it that I got two bad thermostats??

Super frustrated right now.   I will take this thermostat out to confirm its bad. Any thoughts on what I am doing wrong here would be appreciated.

Cheers!!

[70chall440]

Given the information you provided, you have more going on that just a thermostat I think. Things to check

1. As you stated early on, you weren't or aren't getting enough flow across or through the radiator.
2. You could also have some blockages inside the block that is obstructing flow.
3. Your timing is off (too advanced I believe)
4. Make sure you don't have any air in the system, I always drill a 1/8 hole in my thermostats to allow air to escape
5. Make sure your fan is close enough to your radiator to draw the air through; a shroud only works if the fan can create a vacuum or flow through the radiator (shroud helps with keeping the column of air coming through the entire radiator)
6. Check your hoses, I have had them collapse when the system gets hot thus obstruction. Can be had to find/see sometimes.
7. I would definitely recommend flushing the whole system before anything else just so you are starting with a known condition

Hope this helps

[cuda2002]

Thanks for your reply. I appreciate any help on this.

To clarify,  before I replaced the water pump and thermostat, temp would be fine when driving but not good in traffic.  Since I replaced the water pump and thermostat the car heats up while driving.  I've only driven it a couple of times for short durations since the replacements.  The only changes made were the water pump and thermostat.

I can only deduce that that is not a blockage or obstruction. Looks like I get good flow (better than the stock water pump) when the thermostat is out. I haven't driven it with the thermostat out, just to check pump flow. I will take the thermostat out tomorrow and go for a rip around the block and see how it behaves.

Timing hasn't changed.  I checked it yesterday and was good.

didn't drill the thermostat but topped off the coolant in the pump prior to putting the thermostat in.  Later, added coolant to the heater hose.  Promptly overheated after that.  St new thermostat didn't open. Second new thermostat open on the inaugural run but then didn't open when I went out for another drive shortly after the first run. Drilling the thermostat is something I will do before I re-install one.  Begs the question, why don't thermostats come with this hole from the factory. Doesn't the air pass through when the thermostat opens.  I guess that only happens if it opens.  Vapor space might explain why the pyrometer was reading low when the sending units were apparently reading correctly.

I'll check the spacing of the fan to rad but it is a standard direct fan with a 2" spacer (no clutch).  The fan is about flush with the shroud.

Hose on the bottom is reinforced (internal spring) and not collapsing

System was flushed before the new water pump was installed.

Again, I appreciate you taking the time to share your experience.

Cheers!!

[Beekeeper]

I'll throw this out there too since it can add to a problem. I had a tranny cooler on the front of my radiator and once I relocated it, it really helped a lot. My car was a 383 as well with a 22" 3 row radiator. These 22" radiators are barely large enough to handle a mildly performing big block. When you block a portion of it with the tranny cooler, it's effectiveness goes down a lot. If your moving fast enough, the air flow can be forced through both it and the radiator and you describe the problem getting better as you move faster.

In addition to the blockage it creates, The tranny cooler throws off heat and that heat is sitting right in front of your radiator. If you can, try to get the cooler away from the radiator or at least a couple inches in front of it. My advice would be to ditch the tranny cooler and run the lines through your radiator as the factory did. Unless your towing heavy loads or are using a high stall converter, your tranny should be fine.

In an ideal situation, it would be nice to put in a 26" radiator. The factory did this on AC cars and 440 cars because they knew the 22" wasn't gonna be enough. Unfortunately, to get the biggest benefit of the 26" unit, you really need to open up the side support (I think only the passenger side support is narrowed for the bigger unit).

Another option (something I also did on my overheating 383) is to go with an aluminum radiator. Aluminum dissipates heat better but the best feature is they use two super wide thin rows instead of the scrawny rows the original units use. It effectively increases cooling capacity a great deal. Modern cars use radiators with this design and they work better even though they are smaller.

[70chall440]

Beekeeper is all over it; the 22" radiator is minimal at best and with a tranny cooler you effectively reduce its effectiveness by at least a third. Have you tried anything like Water Wetter? Might be worth giving a try, I have seen this product or similar products at local parts stores. People that I know who have used them say they really work, only down side is that you have to remember to add it if you drain the system or otherwise loose fluid.

You might also look at an aftermarket 22" aluminum radiator.

[Cazbah362]

Cuda2002, on top of what Bee and 70 are telling you, I would also consider re-torquing your heads.  Not sure if the status on your motor, but I have had when I replaced my heads the bolts loosen and cause the same issue you are describing.  I went through, re-torqued and no issues. Also, have seen cracked block and heads act like this, but lets rule our everything else before we get to wrapped up on this thought.  Also, lean / timing issue, to lean and too much timing, what carb and AFR are you at?   

Also, the radiator is too small in my opinion, Champion has a great setup for about $250, works well.  Also, do you have a fan clutch?  if not would be a recommendation with a 7 blade type fan, like a factory original.

Keep us posted   

[cuda2002]

Thanks Beekeeper, 70chall440 and Cazbah362 for your comments. 

Yes the trans cooler was on my list of things to check.  I agree that 22" rad is probably marginal for my set-up.  I'm trying to be methodical in my troubleshooting and also trying to learn as I go. I may yet change the rad but I want to make sure that will fix the problem first.

Today, I checked the fan to rad distance.  It is 1". Is that close enough? How close is too close, how far is too far?

I also pulled out the thermostat.  This is the second thermostat I installed, tested it before it went in, it started opening between 175 and 180F.  Tested it again today, doesn't open now. Not even at boiling. How likely is it that two thermostats (Mr Gasket) are bad or fail on first or second use??

Drove the car for about 20 min without thermostat.  It struggled to get to 175 when driving.  Temp started to creep up after idling for 10 min but still around 190F (wasn't a particularly hot day today).  I don't think this fixes my problem but makes it more manageable. So I'm thinking the high flow water pump was an improvement.

I guess I'll need to get another brand of thermostat and hope it works to confirm the improvement.  If it is confirmed, I'll try moving the transcooler, maybe putting a 1" spacer between it and the rad to allow some air movement between the two.  Comments?  Is there another place people mount the transcooler to reduce impact on rad cooling?

Cheers!!

[Beekeeper]

Thanks Beekeeper, 70chall440 and Cazbah362 for your comments. 

Yes the trans cooler was on my list of things to check.  I agree that 22" rad is probably marginal for my set-up.  I'm trying to be methodical in my troubleshooting and also trying to learn as I go. I may yet change the rad but I want to make sure that will fix the problem first.

Today, I checked the fan to rad distance.  It is 1". Is that close enough? How close is too close, how far is too far?

I also pulled out the thermostat.  This is the second thermostat I installed, tested it before it went in, it started opening between 175 and 180F.  Tested it again today, doesn't open now. Not even at boiling. How likely is it that two thermostats (Mr Gasket) are bad or fail on first or second use??

Drove the car for about 20 min without thermostat.  It struggled to get to 175 when driving.  Temp started to creep up after idling for 10 min but still around 190F (wasn't a particularly hot day today).  I don't think this fixes my problem but makes it more manageable. So I'm thinking the high flow water pump was an improvement.

I guess I'll need to get another brand of thermostat and hope it works to confirm the improvement.  If it is confirmed, I'll try moving the transcooler, maybe putting a 1" spacer between it and the rad to allow some air movement between the two.  Comments?  Is there another place people mount the transcooler to reduce impact on rad cooling?

Cheers!!

If you have a fan shroud, you want the fan about halfway in/out of the opening. If you don't have a shroud then I'd say closer is better but best to maintain 1/2" minimum.  I'd get a shroud on it as little things like this help in small ways.

As far as the trans cooler, get creative and find a way to get it away from the radiator opening. If that's not possible, I'd want at least an inch of space in between so air can get in there. If you can remove it and hook back into the radiator, it would give you valuable testing information. If the problem improved dramatically, then you know where to put more effort if running a trans cooler is important to you.

Crazy that you keep finding non functioning thermostats. Get a moroso brand unit. I've had good luck with them. One thing I tried once was to cut the center out of a thermostat so you basically have a restrictor plate. This slows the flow a bit so heat transfer can happen but impossible to stick closed. Not wild about that last idea but it's a way to take that out of the equation while you test out other things. Then when the problem is cured, you put a thermostat back in. If problems reappear, then you know where to look.

[70chall440]

Try a fail safe T stat, locks open if it fails.