Technical Cooling System Problem

I’m looking for some help with a cooling system. I have a BBC that will run cool all day in normal traffic or idling in heavy traffic. Tempature drop across the radiator is 10 to 12 degrees. If I run the car up over a mountain rd it will get hot. It has a four row high efficiency radiator, dual electric fans with a shroud. I was leaning towards building a bigger radiator, until this winter I discovered I had a heater issue. The heater only works at idle, at road speed it blows cold air. I have a March pulley kit, that came with a high flow water pump. I think I have too much water flow. March says impossible? My thought is if the coolant is passing through the radiator too fast that it can’t cool efficiently ? Same for heater core ? What do you guys think. Thanks. Oh March said my problem was the fans were blocking air flow and to turn them off would solve my problem?


Sent from my iPhone using The H.A.M.B. mobile app

 

What about thermostat?

 

I just went through a similar problem.

A couple of summers ago I had a 160* thermostat in it and it always ran erratic. If I was going down the road it was OK. It would run at 160*. If I pulled hard up a long grade it would get up to 200 or so, and if I was in traffic it would go to 220*-225*. That was summertime.

It never pukes, but I don't like that much irregularity.

Then I changed to 180* thermostat and it would run 180* at speed and climb to 210* or so under similar conditions. In traffic it would go to 220*. That was wintertime in Florida.

This year I spent the winter here in 6500 ft. and it started running a little too warm for me. I don't like 220* in the winter. I suspected the thermostat was laying down on me. They were all high flow thermostats in the past.

So, I put a regular flow 190* in it and it stays right at 190*-200* and is much more consistent. Plus, the heater works much better.

I know that the radiator is minimal and the belt driven fan is minimal and the shroud is minimal, but it seems to be working. I never did really figure it out, except that maybe the water stays in the block and radiator longer, giving the coolant more time to absorb and release the heat.

 

Did ya try what they told ya?

 

What do you mean by "high efficiency radiator" ? Looking at the picture I'm assuming the radiator is new. If so we should be able to rule out it being plugged. Years ago I had a BBC pu with the same type of problem after installing a new radiator. Turned out it was the number of fins per inch difference. The shop I got the radiator from had done all kinds of testing thinking it was my truck. Then about 3 months into the problem the guy called me and said he'd found they made a radiator that had a total of almost 3000 fins more. Installed the one with more fins per inch and everything was back to normal. I knew the truck very well as I'd been driving it for about 6 years at the time of replacement

 

Does your lower rad hose have a spring inside to keep the hose from sucking in? This would restrict coolant flow and could be a reason for temp rise and heater not blowing warm air at speed.

 

No help from me but nice clean installation in there.what is the car

 

What is your definition of "normal traffic"? Stop and go, city driving, highway driving?

Did you try their suggestion re: the fans? The lower radiator hose collapsing at speed as suggested by @4tford is also a possibility.

Now for a little "soapbox"
March is correct when they say that it is impossible to have too much water flow causing the issue.

The "coolant moving too fast through the system to cool" theory has been debated at length on this site, and science has proved it wrong.
For those that cling tenaciously to myths, I am going to take one last crack at forever dispelling the Granddaddy of them all when it comes to cooling systems.

The myth is stated as either:

1. Coolant can be pumped too fast through the engine for it to absorb enough heat, or
2. Coolant can be pumped too fast through the radiator for it to cool properly, or
3. Cooling can be improved by slowing the flow of coolant through the radiator so it cools more completely.

NONE of these is true. The simple truth is that higher coolant flow will ALWAYS result in higher heat transfer and improved cooling system performance.

The reason the myth is so persistent, is that: a) without knowledge of fluid dynamics and laws of thermal conduction it does make a kind of intuitive sense and b) it is based on a tiny kernel of truth, but that kernel of truth does not explain the overall system behavior and so, interpreted out of context, leads to a completely erroneous conclusion.

So, let's start with the tiny nugget of truth. If you had a sealed radiator (no flow) full of hot coolant, and subjected that radiator to airflow, yes, the longer you left the coolant in the radiator, the more it would cool. However, if you were to plot that cooling over time, you would find that the RATE at which the cooling takes place is an exponential curve that decreases with the temperature difference between the hot coolant and the air. Put another way - when the temperature difference (delta-T) between the hot coolant and the airflow is large, heat transfer (cooling) initially takes place very, very quickly (almost instantaneously). But as that happens, and the coolant cools, the delta-T becomes less, and the RATE at which further cooling happens gets less and less until the point where the coolant and air are almost the same temperature and continued cooling takes a very long time. This is Newton's law of cooling. To illustrate this lets look at a "quenching steel in a bucket" analogy.

A good example of this law can be seen when quenching a red-hot piece of steel in a bucket of water. At first, the temperature difference (delta-T) between the red-hot steel and the water is huge - therefore the initial heat transfer occurs at a great rate - the steel initially cools very fast - almost instantaneously. However, after this initial cooling, the delta-T is much smaller, so the remaining cooling occurs much more slowly. If you removed the steel after a second or two - it has cooled a lot - but it will still be warm. To continue cooling the steel to the temp. of the water, you have to leave it in there quite a bit longer - because as it cools - the rate of cooling continually decreases as well. In short - initial cooling is fast, but subsequent cooling occurs more and more slowly until cooling that last little bit takes a long time.

So what does this mean? Basically it means, the longer the coolant stays in the radiator, the less efficient the cooling that takes place is - to the point that the rate of cooling is so slow as to be detrimental to overall system cooling. Better to dump the big load of heat right away and go back quickly for another load than hang about waiting for a last little bit of insignificant cooling to happen.

 

Impressive.

 

Possible overheating while driving in mountains could be from the additional load on the tranny. Stall and gear ratio may impact the strain on the drive train.

Poor heater while driving? If you feel the engine temp is otherwise ok, then the heater problem could be from a bad seal between the ducting and the outside air.

You have not mentioned what temps you are seeing, this would help.

 

Have you looked into your distributor total timing and when it comes in?

 

There was a guy on the local Craigslist that says his wife knows how to handle a hot BBC. I could message him and see what he knows.

 

Excellent explanation! Let's hope this myth finally goes away for good!

 

I think this is most likely the answer right here. Think about it, if the coolant temp is increasing, why would the heater get cool? Right? If the coolant is heating up, and the coolant is circulating as it's supposed to, how could the heater start blowing cooler air? HOw is that possible. Well, it's only possible IF the coolant isn't circulating. So your problem isn't that the coolant is circulating too fast, @Ebbsspeed put that theory to rest, the problem is that it isn't circulating enough. Check for that spring in the lower hose.

 

I have used 2 of the Milodon thermo's and they solved my problems ( Blown BBC Willys) and worked great!
https://www.summitracing.com/parts/mil-16400

 

That is too damn funny!

- EM

 

Are your fans pullers or pushers (mounted in front of or behind the radiator)? If they're pusher type fans, there is a very good chance they are blocking your radiator which is a good reason why you're running cool at idle or slow speeds (when the fans are running) and not at highway speeds (when the fans are not running).

- EM

 

The lack of heat from the heater is what bothers me at this point. I assume you have a valve on the system to control the water flow through the heater so you could slow it down. I'm assuming one heater hose is connected to the water pump near the inlet and the other is connected to the elbow next to the thermostat housing. That should provide good flow and good heat as the pump should pull coolant in and it will be forced out of the intake manifold. That flow should only be stopped if the pump quits working or something blocks the flow. I have seen a case where the impeller comes loose on the shaft when it heats up and expands but that would be very rare. If the lower radiator hose was being sucked closed it would create more flow through the heater core, not less. Even if there is not enough airflow through the radiator, the heater should blow hot air and get even hotter as the coolant gets hotter.

 

Heater may just be plugged. Or your engine doesn't like the altitude. Perhaps try a separate transmission cooler?

 

the heater hoses look to be in from the same spot in the intake. you need to move one of them to the water pump to get enough flow.

 

Put together a BBC in an OT car. Had similar setup. Put a 190 thermostat in shortly after cleaning the radiator. Radiator was new, engine had 150 miles on it when installed (dyno time and 1 track day) sat for 2 years before being used again. New radiator had piles of rust in it. We were concerned so we flushed the coolant after having the radiator professionally flushed. The car had one large puller fan on it, I added another and havent had a problem yet. I still think it was the thermostat all along, just getting clogged up from the same rust problem we found in the radiator. I have pulled it a few times to be sure its not going to have an issue and its minimal now. This particular car i speak of has no heat so can't help you there. March pulleys don't underdrive the water pump from what i understand, That's what we run also.

 

Spent time in Eng. heat transfer & thermo study. Often a sticky wicket. Ebbsspeed that is one Excellent description! Bravo!

 

"the heater hoses look to be in from the same spot in the intake. you need to move one of them to the water pump to get enough flow."
I think the one heater hose by the thermo housing you see is coming off the water pump. BBC run a rubber 90 deg. in that area...........................................

 

First off, that motor is beautiful
Second that thermo dynamics lesson was incredible!!
What about an air pocket???
Oldsmobile 350 Diesels would blow their head gaskets, and cause air bubbles in the heater core...resulting in no heat. One of the first things my customers would complain about.
Is your radiator lower than these other components?
Am I the only one that drills an 1/8” hole in thermostats, to enhance bleeding???
Good thread, especially for us down here in Florida
JT


Sent from my iPhone using The H.A.M.B. mobile app

 

An infra red thermometer will help quite a bit in diagnosing the problem.
You want to get a base line of temp at the thermostat housing. It should closely match the thermostat temp rating.

Shoot At the heater hose in let and out let. The inlet should closely match the baseline, the outlet be significantly cooler showing the amount of heat leaving the coolant and the heat entering the cabin.

Your upper hose entering the radiator should closely match the baseline. The lower hose should show a significant heat loss demonstrating the heat shedding efficiency of the radiator.

The thermostat is important part of the system, it should remain closed and allow the car to warm up to temp before allowing any flow. The temp gun should show very very very slow warming on the housing until it opens then spike up upon opening. If the temp gun shows gradual warming on the housing without spiking it's stuck partially open or there's too big of hole drilled in it.

 

I can't see the belt system but are you absolutely positive that you have the correct rotation pump for the belt system you have on the engine? A pump with the wrong rotation will cool at an idle or low speeds but the engine will get hot at road speeds or when pulling a hill. I first ran into that when some guy stuck a mid 60's 327 in an 81 Camaro and then bought a water pump for the Camaro rather than the V belt 327. Car held temp fine idling or at low speeds but the temp shot up as soon as it hit the highway. That's just a thought, if you know that you have the right pump for the belt system scratch it off the list.

 

does coolant absorb heat as fast as it gives it up?

 

That depends on the temperature difference between the coolant and the heat source or the temp difference between the coolant and the air.
The bigger the difference the faster it goes.

 

Oh you've got to be kidding me

 

so the hotter the engine gets, the quicker the cooler, coolant will absorb the heat, making the coolant hotter than the air, making it release the heat quicker. sound like a wash.