Overheating on the Freeway - What Are Your Possible Causes?

rust is still magnetic, get creative with their placement. [ old speaker magnets, rare earth ones off ebay ]

 

Listen to Larry the "Wizard"...he has helped me more than once to fix issues that I had
including this overheating problem...she now runs at all times at 180-190.

Buick Eric / Oregon :3gears:

 

If you plan to do a "running engine" block flush, do it before you swap out or rebuild the radiator. That way you are not running all the crap through your new radiator. And, as stated, remove the thermostat. There are "block flush" products out there. Some, on here, may have product recommendations of what to, or not to, use.

 

Agreed, Devon.

 

In a nutshell, your possibilities are:
1) Lack of flow
1a) Airflow blocked to the radiator
1b) Lack of coolant flow (i.e. scale clogs, collapsed lower hose, poor pump, etc.).
2) Engine creating too much heat
3) Poor heat conduction between the metal and coolant (due to rust or scale or other gunk)

Fans are irrelevant at highway speeds. A few years ago I calculated something like 18,000 CFM at 65MPH. (A 2000 CFM fan will help at idle when there is no air movement, but as you can see it won't have any impact on the highway - and can even interfere with airflow.)

-BC

 

Still too early to say for certain, but it's looking as if I might have to retire my old radiator. Too bad really... it's been with us for 50 years now and even survived a couple of nasty front-end collisions.

Anyhow, who are your most-favorite and least-favorite suppliers for new radiators? I was thinking about picking up whatever they had at NAPA, but thought it best to ask those with experience instead.

 

I'd recommend bringing it to a local radiator shop and having it recored.

-Bob C.

 

You didnt say which engine you have. The 300ci is easy to get a radiator for and fairly cheap. Mine already had the 401ci swapped in but still had the old 300 radiator cobbed in it. So i went with this company to get a correct replacement: http://www.usradiator.com/buick-gs-1965-66-v8-401-radiator-7428.html

The radiator was packaged very nicely, shipping fairly quick and my only issue was going from the 3 core to a new 4 core with the mounts but surely isnt the manufacturers fault but mine. What i do like is they show detailed pics of most of the radiators showing the inlet/outlet options for each engine so you know your getting the correct one you seek.

Here is the page for all radiator listings for that car for the various engines, options, brass or aluminum. http://www.usradiator.com/radiators/buick.html?cat=198

 

I never had a problem like that and all I do is turned out to be weak mechanical advance springs in the distributor

 

Here's an update...

My neighborhood is surrounded by what I consider a great "test-track". It has little traffic, goes downhill a few miles at 35-45mph (posted speed limits) and uphill the same distance at 50mph (also the posted limit). It's not the freeway, but perfect for what I've needed since bringing this car back to life. I used to be able to drive this loop at least 3 laps before the temperature would jump from 200 to 225. Shortly after getting this thread started, I couldn't even finish 1 lap without the temperature jumping.

1) The old vacuum advance was leaking. Replaced that. Still overheating.
2) Before rodding (or replacing) the radiator, I installed one of those Tefba filters at the radiator's inlet port to catch what garbage might've been hiding in there. It caught everything from rust debris to "sand" to chunks of excess gasket sealant (new and old!). I couldn't believe how much garbage was in there and didn't want to know how much had already lodged into the radiator and core prior to my installing that filter.
3) Pulled the radiator and had it inspected. According to the shop, it was "substantially blocked" but still in good solid enough shape to keep in service after a good cleaning. I decided to have it rodded out and save the decision of a new radiator for later. (Looks as if this 50 year-old radiator will be staying in our family for a little while longer.) When the shop was done with it, it looked as good as new.
4) Put everything back together.
5) Made every excuse to take the Skylark out for more test-laps ("I'm taking the boys to the playground", "We're out of milk", "Donut run", "I thought I heard a noise from several miles away that needs to be checked out", etc.) I was able to go further each run, but every time would eventually have to limp home because the Tefba filter (which was protecting the radiator as intended) kept filling up with leftover garbage from the block. As the filter caught this stuff, I could remove it from the system after each run. For every additional run, there was less garbage to remove. Nowadays, there's still some debris being caught by the filter, but not enough to create blockage in it. My temperature is no longer jumping to 225. It's holding steady at 200.

While that filter has been a life-saver (more of a radiator-saver) for me, I've still got other work to do here to improve things further: reverse-flushing the system, check my timing, mixture, etc.

I vaugely recall this car running at 195 degrees or less a couple decades ago, but I rarely trust my memory anymore. What are your normal (or optimal) temperatures for the 300 V8 at street and freeway speeds?

 

WOW, that's a lotta crap in the cooling system:shock:
Never considered filtering the coolant.

 

Lately, the 1965 300 in my 1964 Sport Wagon runs around 190 with a 180 stat ... this is true at idle, at speed, and most places in between. Transmission is a ST300, four-barrel intake and carb. Radiator has a small leak and will be re-cored this week.

Greg

 

Where did you get the filter?

 

They're produced in Australia, but there's a Jaguar parts company in Texas that distributes them. Here's their link to the filter's info: http://www.v12performance.com/Tefba.html

My favorite part about this style of filter is that I can clean it out without having to drain any coolant. It comes with two reusable filter types: coarse and fine. I'm sticking with the fine filter for the time being and keeping the coarse filter in the trunk in case it becomes the more appropriate option someday.

 

Good to hear you got it down, and smart move to use the Terba filter to remove gunk from the system. We make aluminum radiators for these old cars, and experience shows that if it overheats at idle, you don't have enough air pulling through the core. If you overheat while going down the road, you either don't have enough radiator surface area (which isn't your issue, as the original should cool adequately for a stock set-up) or you have other issues (blockage up front, bad water pump, leaking head gaskets, or the most common issue: running lean due to vacuum advance problems or carb problems).

Assuming everything else has been verified / fixed, you can also use something like Redline Water Wetter, which is added to your coolant and can drop the temps a few degrees.

 

Hey I'm new to this forum. How do I post ?? I find this confusing.

Hollowman thanks.

 

I'm glad I found this thread.
I have the exact same problem
Thanks for posting
And thanks for the responses
It answers all my questions

 

Found this on line thought you might be interested. The clear unit seams like the way to go, don't have to open to see what's in there and you can see coolant flow.
http://www.ganofilters.com/

 

After many runs around town and short runs on the freeway, I was still catching more of that garbage with my coolant filter, eventually causing the engine temperature to crawl back up (fortunately, never back to 225*). I decided to bypass the heater core since it likely also got filled up with the same debris that "substantially blocked" my radiator (before I had that rodded out). A month after doing that and clearing the Tefba filter regularly, the garbage in the cooling system was almost completely cleared out. A recent flush confirmed that the coolant was finally clear of debris (it used to burp sandy chunks out of the petcock during a coolant flush, but no more).

I'm able to drive the Skylark around more than I used to, but the drives are short as I use it for errands around town. As I'm taking it out for longer runs around town (not many opportunities for me to get on the freeways lately), I'm seeing that while the engine temperature sits around 195* for awhile, it'll eventually walk up to 210* if I stress it by either sitting at a light too long (keeping it under load in Drive instead of Neutral) or going uphill. I adjust how I'm driving to prevent the vaccuum from staying low for too long, but the recoveries are minimal. Also, once it climbs up to 210, I can never get it to fully recover... getting back down to 200-205 at best.

I haven't tuned anything since bringing the Skylark back to life this year, so I thought I'd at least check timing and such to ensure that nothing was grossly off:
1) Dwell was at 29.5*. I decided that was close enough to my desired 30* for now.
2) Initial timing was at 12*BTDC. I turned it down to 5*BTDC for now. I'll turn it down to 2.5* (the recommended number according to my books) on an upcoming weekend.
3) The vaccum at the vacuum-advance typically reads 14-21, depending on how I'm driving. The exception is when I'm stopped and in Drive. Then, it drops to about 8. Should it be that low? (Sometimes, I'll pop it into Neutral just to take the load off and the vacuum will jump back up along with the engine speed.)
4) In case I haven't mentioned this before, I'd confirmed that my thermostat is opening when it should. Haven't confirmed its closing point.

I'm thrilled that it's no longer jumping up to 225*, but am I over-reacting to this new "high" temperature of 210. Is 210 acceptable or close to hurting this stock engine? Is 195 a reasonable expectation or not?

I've been with this Skylark my whole life and really wish I'd paid closer attention to the temperature back when the car was in its prime running condition during its "younger" years. Then, I'd have a better reference point.