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Evaporust as coolant or hot flush?


Ken_P
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A thermostat only "throttles" the coolant flow.  If the system runs close to thermostat opening rating, ie: 165* for a 160* thermostat, it is efficient and has reserve cooling capacity.  Once the thermostat reaches wide open, ie: 175 appx for a 160* stat, you have reached the limits of that cooling system to control the temperature under those operating conditions.

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It's not quite as simple as "all the coolant flowing through the radiator will drop 20 degrees." The thermostat isn't an on/off valve, but can significantly vary the speed of the coolant flowing through the system. In that way, it can make the coolant hotter overall as it spends more time in the engine. As it reaches the rated temperature, the thermostat opens and flow increases and the radiator cools the coolant. If there's not enough engine heat to keep it above the thermostat's rating, the thermostat starts to close again, slowing flow to heat up the coolant inside the engine. It's crude, but it's pretty good at regulating the temperature if the system is healthy.

 

The problem is that if the engine is putting out 190 degree coolant and the radiator can only drop it 10 or 15 degrees, and you're running a 160 degree thermostat, then the thermostat will simply run wide-open all the time and will no longer be able to regulate it. Then it's up to the radiator to keep up with the heat being added to the system by the engine. If the engine is making more heat than the radiator can shed, you overheat (obviously). So either the engine is putting so much heat into the coolant that the radiator can't keep up, or the radiator can't reject it fast enough, or some combination of both. But once the thermostat is wide open, its job is done and now the radiator has to get rid of the heat or die trying.

 

There's more to it since the radiator's delta-V isn't a fixed number (it won't always drop coolant temperatures 20 degrees, for instance) and ambient air temperature is obviously a significant factor. My '41 Buick typically runs at 180 or so, but yesterday with temperatures around 48 degrees it barely hit the 160 rating of the thermostat and I could watch on the gauge every time the thermostat opened because it would drop to 150 before gradually climbing back up to 160--that's the thermostat opening and closing and the radiator being almost too good at its job.

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1 hour ago, Matt Harwood said:

It's not quite as simple as "all the coolant flowing through the radiator will drop 20 degrees." The thermostat isn't an on/off valve, but can significantly vary the speed of the coolant flowing through the system. In that way, it can make the coolant hotter overall as it spends more time in the engine. As it reaches the rated temperature, the thermostat opens and flow increases and the radiator cools the coolant. If there's not enough engine heat to keep it above the thermostat's rating, the thermostat starts to close again, slowing flow to heat up the coolant inside the engine. It's crude, but it's pretty good at regulating the temperature if the system is healthy.

 

The problem is that if the engine is putting out 190 degree coolant and the radiator can only drop it 10 or 15 degrees, and you're running a 160 degree thermostat, then the thermostat will simply run wide-open all the time and will no longer be able to regulate it. Then it's up to the radiator to keep up with the heat being added to the system by the engine. If the engine is making more heat than the radiator can shed, you overheat (obviously). So either the engine is putting so much heat into the coolant that the radiator can't keep up, or the radiator can't reject it fast enough, or some combination of both. But once the thermostat is wide open, its job is done and now the radiator has to get rid of the heat or die trying.

 

There's more to it since the radiator's delta-V isn't a fixed number (it won't always drop coolant temperatures 20 degrees, for instance) and ambient air temperature is obviously a significant factor. My '41 Buick typically runs at 180 or so, but yesterday with temperatures around 48 degrees it barely hit the 160 rating of the thermostat and I could watch on the gauge every time the thermostat opened because it would drop to 150 before gradually climbing back up to 160--that's the thermostat opening and closing and the radiator being almost too good at its job.


 

All above does not apply to cars using a winter front or shutter thermostat in front of the car..........that setup does not regulate coolant flow. 

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Thanks for answering Matt, Yes, I understand how a thermostat opens and closes. . . .

 

The OP is fighting a cooling systems that is not functioning at maximum efficiency (unlike your Buick) He is flushing and filtering to increase the efficiency of the system through better coolant flow in both the engine and radiator. He was discussing possibly using a colder thermostat than recommended when new. 

 

We all want a cooling system that can easily shed whatever heat our engine can produce, whether it is a slow 4th of July parade or a lugging climb up a steep hill in high gear on a summer tour. 

 

My point was about how to cope or compensate for a bad cooling system. How to 'get by' when it isnt working as it should. (Yeah I know Ed, it should be fixed to the highest standards, but until then . . .) 

 

As Ed mentioned the water thermostat information doesn't apply to an external shutter thermostat system. In that case the water just flows and the shutters open/close to block airflow and essentially make the radiator less efficient and function like a "bad' radiator. Years ago as the shutterstat equipped car aged, it was common to wire the shutters open for maximum airflow and because the old system was bad, the inefficiencies of rust and crud acted as a 'thermostat' such that the engine wasnt operating too cold even with the shutters wide open. Like your well sorted Buick would without a thermostat. 

 

If you have a bad cooling system (that cant shed as much heat as it should) would not installing a colder thermostat that opens sooner and sends the colder water to the bad radiator, (where it cant shed as much heat) early.

And because it is sending the colder water to the bad radiator sooner (and the engine continues to make its normal heat load) the bad inefficient cooling system is better able to keep the engine operating within an acceptable range? 

 

My question (putting a cold thermostat into an inefficient system) is not about fixing it right (which the OP is striving to do) but how to compensate until it is sorted out and all up to snuff. 

 

 

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1 hour ago, m-mman said:

If you have a bad cooling system (that cant shed as much heat as it should) would not installing a colder thermostat that opens sooner and sends the colder water to the bad radiator, (where it cant shed as much heat) early.

And because it is sending the colder water to the bad radiator sooner (and the engine continues to make its normal heat load) the bad inefficient cooling system is better able to keep the engine operating within an acceptable range?

 

Allowing the coolant to circulate into the radiator sooner (with a cooler thermostat) isn't really going to change anything in the long run. The cooling system is eventually going to reach equilibrium at the same temperature (i.e. when the radiator is rejecting as much heat as the engine is putting in). Whether you have a 120 degree thermostat or a 190 degree thermostat, if your car runs at 200 degrees, it's going to run at 200 degrees because it's a function of the radiator and the engine, not the thermostat, which will simply remain wide open. The only thing a cooler thermostat might do is cause it to take a little longer to get that hot. It will eventually get there anyway.

 

If X MPH generates Y BTUs of heat, the thermostat can't do anything about it if Y is greater than its temperature rating.

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Posted (edited)
6 hours ago, Matt Harwood said:

There's more to it since the radiator's delta-V isn't a fixed number (it won't always drop coolant temperatures 20 degrees, for instance) and ambient air temperature is obviously a significant factor.

 

That's right Matt- the temperature drop should actually go up for a given radiator with a higher inlet temperature, because all heat exchangers are more efficient with a higher differential temp (in this case between the water temp entering the radiator and ambient air temp) - also why cars are more likely to overheat on a hot day.

 

I think I'm struggling with a heat capacity removal problem. This is also supported by the fact that the car got hot when I ran it without a thermostat on a run a few weeks ago.


There is additional friction in the engine because of the new rings, but I anticipate that effect should be starting to fade, because the new rings have a little over 500 miles on them now.

 

I put in new evaporust today, and will keep cycling the engine. I'm also going to try and work out how to best do an accurate radiator flow test with the engine in the car, and I'll do that as part of the next cycle when I clean the gano filter, and or renew the evaporust.

 

Edit: the below pictures are in the head and the top of the radiator that I took with a new inspection camera I just got. Can't get it very deep without pulling a freeze plug, but interesting. A lot of the surface looks mung covered, rather than rusty, yet all the crap my filter is catching is magnetic. Temp gauge is for fun. Sitting at idle at a stop light just after the car fully warmed up. Hadn't been above 30mph yet.


This is after hot flushing the block for a week, running the pump 12-16 hours a day (it was so noisy I shut it off at night so I could sleep!!!) and one cycle running evaporust as coolant. We'll see what it looks like on the next cycle.

 

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Edited by Ken_P (see edit history)
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Did you check the water distribution tube behind the water pump? It may be rotted out and the rear of the engine might not be getting proper water flow to it. Since you have a newer radiator core with good flow I would rule the radiator out at this time. I know that you checked the fuel and ignition system already but check it again.There are two jets in that carb that each feed 4 cylinders and one of them may be getting clogged causing half of the engine to run lean sometimes.  Make sure the distributor is working properly, that the weights are advancing, and check the spark plug wires and make sure the fittings are nice and tight and also check the condition of the spark plugs.  A fouled out spark plug can cause you to run hot. You might want to do a quick compression test just to verify that you have consistent compression. If you have a digital thermometer check various spots on the radiator, cylinder head and exhaust manifold.

 

The 1937 120 is a fine car and it should give you a lot of trouble free miles once tuned in. Packard would not have sold a bunch of 120's in 1937 if it was a temperamental car.

 

Good luck.

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FYI- There is a link to the Packard Club website which you will find on the forum. There is a "Tech Tip" section on the left hand side of their web page with some good pointers. 

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Posted (edited)
2 hours ago, Tph479 said:

FYI- There is a link to the Packard Club website which you will find on the forum. There is a "Tech Tip" section on the left hand side of their web page with some good pointers. 

 

TPH - lots of good info here. Thanks! I did check the water distribution tube. All fine. Carb was professionally rebuilt about 5 years ago, and kept clean since then. Plugs show an even distribution across all cylinders. Been through the entire distributor, and installed a completely rebuilt spare, just to rule out any ignition issues. Head was recently off for an in-frame overhaul, compression is all consistent across the board. Thanks for the thoughts!

 

I've been through pretty much the entire list on the Packard Club website - a lot of the mechanical work is detailed in my project blog on PackardInfo.com. So far, all sat. The only thing I haven't done is re-jet the carb for E10. Agree the 120s are great cars. I'm a fan, just trying to get it all the way sorted.

 

 

Edited by Ken_P (see edit history)
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Posted (edited)

I have been helping Ken on the phone. When it’s “all boiled down to gravy”, (sorry, I can’t help myself) it probably is going to be a radiator that was replaced with a core that was too small, and doesn’t have the correct flow rate. One step at a time, let’s get the block clean first.

Edited by edinmass (see edit history)
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If the block is encrusted with mineral deposits (limescale & calcium) which is what I think I am seeing in the photos - all the Evaporust in the world won't remove it.You would need to use a chemical scale remover similar to what we use in boilers. However, whether that would agree with the other types of metals and materials it would be in contact with (aluminum, brass, rubbber etc.) is another matter.

 

As Ed suggested - I would seriously look at the radiator. It may have "checked out" at the radiator shop but something is not right.

 

 

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37 minutes ago, Terry Harper said:

If the block is encrusted with mineral deposits (limescale & calcium) which is what I think I am seeing in the photos - all the Evaporust in the world won't remove it.You would need to use a chemical scale remover similar to what we use in boilers. However, whether that would agree with the other types of metals and materials it would be in contact with (aluminum, brass, rubbber etc.) is another matter.

 

As Ed suggested - I would seriously look at the radiator. It may have "checked out" at the radiator shop but something is not right.

 

 


Terry, that’s kind of what I thought, too, except: the first round of evaporust turned black quickly, and all the gunk coming out of the car is magnetic. I’ll do this next round of evaporust and peek again. If it looks the same way, I may try to find some way to remove the scale, if that’s what it is.

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Besides rust, and hard water scale, one also must consider organic’s causing a problem. Each one must be dealt with in a specific way. One issue at a time. Fix a known issue, and go on the the next. Throw thought and intelligence at it.......not money.

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Maybe a stupid idea but do you have proper airflow through the radiator? Is your fan blade in good position and close enough to the radiator? Is it correct size and number of blades for your car?

 Once I had an old car with modified electric fan installed but overheats...all checked again and again...carb,ignition,water pump,replace heater,replace temperature gauge,remove thermostat and so.The problem was that some stupid do the +- in the electric, fan turns opposite way.Don't suck air in,just hardly tried to push the air out from the engine bay against 50mph incoming wind. I changed the polarity and all fine. In your case its not the problem except the fan blades are in correct position :)

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Posted (edited)
22 hours ago, aron_budapest said:

Maybe a stupid idea but do you have proper airflow through the radiator?


Not a stupid question! Factory fan, engine, radiator (except new core), etc. No shutter system, etc. I did check air flow, seems fine.

Edited by Ken_P (see edit history)
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5 hours ago, JACK M said:

The old guy I worked with would toss a shop towel in the direction of the radiator.

If it stuck there was enough air.


Then I’m sat!

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Just thought I would give an update- another 50 miles, and the evaporust is black again. Much less crud in the filter and in the fluid this time, so I think I’m making progress. 
 

I was going to pull the radiator this week, but just for the heck of it, I’m going to flush the block and core with water, and do one more round of evaporust before I pull the rad for flow testing. I’ll have to take shorter trips so I don’t boil over, now that it’s getting warmer, but I want to make sure the block is squeaky clean before I drop in a new radiator (if that’s what it takes). 

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  • 2 weeks later...
Posted (edited)

After more reflection, I went ahead and pulled the radiator. Glad I did. I had pulled the water distribution tube about 600 miles ago, and it was clean. I pulled it again after pulling the radiator, and FOUND A WARNING LABEL in the back hole of the water distribution tube!!!

 

I don't think this alone caused overheating, but it certainly didn't help! I think it's worth pointing out that I bought this car in 2015, and do not recognize the warning label, so who knows how long it's been in there.

 

I also looked down the block with the water distribution tube removed, and there seemed to be quite a bit of debris laying in the water jacket. I set up my evaporust flush rig to go in the heater supply line from the back of the head, fabbed up a plate to block off the thermostat housing, and have the flush exiting the water pump. Just for fun, I put the gano filter in the discharge.


Overnight, it plugged up the filter! After work today, I'll clean the filter, flush the block with water again, and I'm going to try and pressure wash/ mechanically agitate the block where the water distribution tube goes. (Note, I did all of this last summer while I was doing an in-frame overhaul, but it seems the evaporust has knocked a bunch of crud loose).

 

I also have the radiator at a shop for flow check and inspection. Should have those results next week.

 

One additional note - before I tore it all down, I got it good and warm, and pulled out my heat gun.


With the gauge at about 190F, and the engine idling, the radiator showed an even 25-30F drop across it. Top of the head and the water jackets were all within 5 degrees of each other.

 

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Edited by Ken_P (see edit history)
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You're making good progress and doing it right. Sometimes there's just no substitute for getting in there and scraping the gunk out. I had good success using some engine block cleaning brushes from Summit Racing (https://www.summitracing.com/parts/mor-61820). Sometimes I jammed them in there and scraped them around and sometimes I mounted them on my cordless drill and spun them while working them around the water jacket. A whole lot of crud came out that way. Also try a magnet on a stick, which will pull out a lot of debris that might be too sticky or heavy to be reached any other way. This is AFTER the Evapo-Rust bath:

 

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You're getting it and I think you're close. You're eliminating all the variables.

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Thanks for the encouragement Matt! Agitation is in my future... the three pictures are near the front of the block, middle, and back of the block down the water distribution tube hole. You can really see a big pile of crap by #8 cylinder.

 

I’m going to start with a long enough metal rod to reach the back, sharpen it a bit, and go to town. Magnet too. All of my tools are about 8” too short. Tried using a piece of tube attached to my shop vac, but not a lot of joy. I’ll probably also order a set of those brushes before my next evaporust treatment.

 

I though my filter was clogged, but I think my pump may have died instead. Filter was pretty clean.

 

 

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it seems some are using EVAPORUST AND SOME THERMO CURE WHICH IS MADE BY EVAPORUST     IT SEEMS THE BEST BET IS THERMO CURE WHICH IS MAKE FOR COOLING---   I AM HAVING SLIGHT OVERHEATING ON A EARLY 30S CARS        LOOKING FOR COMMENTS   !!!!!

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I saw somewhere that Evaporust and ThermoCure were the same chemicals just different strength.

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4 hours ago, broker-len said:

it seems some are using EVAPORUST AND SOME THERMO CURE WHICH IS MADE BY EVAPORUST     IT SEEMS THE BEST BET IS THERMO CURE WHICH IS MAKE FOR COOLING---   I AM HAVING SLIGHT OVERHEATING ON A EARLY 30S CARS        LOOKING FOR COMMENTS   !!!!!


Overheating can be caused by many issues. Running evapo may or may not help it. First determine why the car is hot.

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thank you for your  comment      I am aware of the reasons for overheating----timing,, thermostat ----bad pump,leak in block,,,,,don't think these are my issue     overheats when air temp is extreamly high and since I do not want to  pull front of car for the 10th time going to address the possibility  the Rad is partly clogged     just looking for the best treatment for the buck

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In that case, it's a very good reason to try it. Just dump what is in there, flush with clean water, and drain as much as possible. Run straight evapo in the system. The more you drive it, the faster it will work. I won't harm anything If it turns black in three days or less, drain it and add all new evapo again. Depending on the contamination you may have to do it three or four times. Is a lot easier than pulling the car down. In severe cases it won't solve the problem. MOST of the time, you will get away with it. 

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1 minute ago, broker-len said:

I am guessing you recommend evapo rather that  thermo care  ???


 

Yes..........thermo cycle the car several times a day before and after work, and drive it as much as possible. Cleaning out the radiator can take time........low flow takes longer to clear up than trash in the block.

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Posted (edited)
19 minutes ago, broker-len said:

I was told thermocure was made be the makers of evaporust  and is specifically for cleaning radiators


Yup........but I have never used it. I have used regular evapo for years, on twenty cars.........if something works, I don’t change it. 
 

Thermocure comes in a quart. Don’t imagine it will solve the issues that I have come across.......sometimes it takes 10-12 gallons to get a car’s rust issues resolved. 

Edited by edinmass (see edit history)
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I am reading another thread       how important is it to put some kind of filter -----on upper hose   ??   how did you arrange it  ??             did you run evaporust  straight   ????

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Yes, run it straight. Filters are not always necessary.......depends on conditions. I usually pull the water jacket cover and freeze plugs..........and clean it out that way before the treatment.......most don’t.

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You don't have to dump EvapoRust when it turns black.  Drain into a pail and let sit for a day or two, all the black stuff settles to the bottom. Just carefully pour the clear off and reuse, adding in new to top off.

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47 minutes ago, Jim Bollman said:

You don't have to dump EvapoRust when it turns black.  Drain into a pail and let sit for a day or two, all the black stuff settles to the bottom. Just carefully pour the clear off and reuse, adding in new to top off.

 

Jim, thats not my experience. Maybe the heat in the system also turns it black or it doesn't settle out. Maybe someone can post photo of drained fluid after a few days. There is one member now who is running it this weekend, so I will ask him to try it. Ed

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Posted (edited)
33 minutes ago, edinmass said:

There is one member now who is running it this weekend


Make that two.

 

I re-cleaned/flushed everything, and got the pump running again. The heat apparently made the hub and impeller in my cheap harbor freight pump separate. New impeller, and back in business.

 

Also, I just dumped out a bucket of black evaporust. 2 weeks sitting, no change in color 

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Edited by Ken_P (see edit history)
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Well, I’m not flushing anymore for a day or two! Pump impeller failed again - turns out they mean it when they say it can’t pump hot liquid.

 

Northern tool has a pump that can handle hot liquid, but it has plastic fittings in a weird thread size, so I ended buying  a wort (beer in the process of being made) transfer pump from Amazon. Stainless steel, 5 gpm - perfect. It will be here Tuesday, so we’ll see how it works.

 

The best part is, I brew also, so I may be able to clean it out and use it for that too!

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