As per subject. Had a recent rebuild on the ol' engine, and she's running better than in some years. Problem is that the longer I drive it, the higher the temperature gauge goes! I thought it was a gauge/electrical problem, but after installing a new electrical temp gauge, it seems not. Here's what I've done:

Tried taking the Heater core out of the loop in case it might be plugged. - Same issue
Water pump replaced - Same issue
Using a 195 thermostat (was using a 180, but again, same issue)
I had of course done a RAD flush, which was mildly, but not completely helpful with the Champion
Changed out the RAD! - Was using Champion, figured I'd try the old rad (leak free, better cooling it looks like) - Same issue, just takes longer to get into the red.

So. That's where I stand. The old Plymouth RAD does keep the engine cooler longer, but inevitably I'm moving into the 210+ area, edging into 230 (the redline on the gauge). Temp gauge is in the top hose and seems pretty correct. In dash temp gauge appears even hotter.

Anyway. Any thoughts here? I'm not getting either the flow or the cooling I need to keep a constant temp. I suspect that if I'm cooling properly, we'd probably stay around 195-210. Doesn't happen.

Any help is hugely appreciated! Thanks!

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

Does it make a diffefence if you go out on the highway or stay around town?
What are you using for a fan?

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Official Cookie and Mater Tormentor.

Hi Slantzilla. It does, actually. Seems to get hotter the longer I'm on the highway. In the city streets it tends to take really long for the temps to climb.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

When my engine had a rebuild it ran hotter for 1500 miles. Everything is tight and needs to brake in over time.

Just some thoughts:

Retarded timing can keep a lot of heat in an engine that would go out the exhaust is timed correctly.

Assuming the heater core is plugged, and bypassing it yealds the same result; less total cooling capacity.

Changing thermostat rating from 180 to 195 will keep more heat in the engine, but dose increase the delta T relative to ambient temperature resulting in the radiator to be able to shed heat faster in theory. In practice I think the added cooling would be negligible in this application.

Is there an airflow restriction to the radiator, and or is the fan installed correctly to suck not push air?

Is the thermostat install in the correct orientation; the spring side of it facing the head so it sees hot coolant?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Double check the temps with a cheap heat gun to be sure. Did you have any cooling issue before the rebuild.

I have an 11.5 to 1 race motor that the fan never runs on if I am moving at all.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

If you are looking at the factory gauge only, then you have very little idea what the actual temp is. Maybe you mean it is a new electrical aftermarket temp gauge. If factory only, then either look with a heat gun (not the most accurate, but OK), and then install a good quality temp gauge. Basically everyting said above is also good to check. Timing and miles after rebuild can be significant, as Bill says. Depending on how well the rebuild shop cleaned the block, you could still have some blocked cooling passages. Is there gunk or rust/chunkiness in the rad fluid (coolant+water)? Water wetter can help too, as another thing to try.

Lou

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Home of Slant6-powered fun machines since 1988

Does it look like you have good coolant flow into the radiator when the thermostat opens? What type of fan?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Make sure your electric fans are moving air the correct direction (front of rad to rear of rad). If they're trying to move air forward while your car's forward motion is trying to move air rearward, not much air will flow across the rad.

Also, please provide more detail: will the engine heat up if it's left idling, or only if you're actually driving? Is it worse at higher road speeds, or low speed/stuck in traffic? Any other symptoms of overheating (pinging, power loss, actual boiling/steaming, unhealthy too-hot smells from under the hood)?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

This will put some folks on edge... Did you modify the head gasket in any way when you installed it? I've seen slant six guys punch the coolant passage portion of the head gasket out in the middle of the path front to rear.

Don't do that. The gasket is supposed to block off the passages that open between the head and block in the middle of the flow path. The coolant has to travel the full length of the block, only transferring at the rear-most passages through two passages.

Just in case..... Not saying you did that, but it will overheat your engine if that happened.

CJ

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Part of Tyrde-Browne Racing

To respond to SlantSixDan about symptoms, it does tend to heat up quickly on the freeway. Idling is not an issue. I could probably idle the car for 10 years without any crazy overheating. It is much worse high speed than low speed.

When we're in the add-on temp gauge's "Red Zone", there definitely is some ping. Otherwise, nothing in terms of crazy engine symptoms. No boiling, no weird smells, nothing crazy. Just a gauge that's on fire!

This is also not a fan thing. Fans are correctly directed.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

If it will idle cool forever but heat up instantly on the highway you have obstructed airflow through the radiator.

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Official Cookie and Mater Tormentor.

I don't agree, unless the electric fans are actively fighting against you by trying to move air from back to front while the forward motion of the car is trying to move air from front to back—possible, but not a terribly likely situation. Barring that, the general rule is that low-speed/stuck-in-traffic overheating is insufficient airflow across the radiator (the car's motion isn't helping, so you have inadequate fan capacity) while high-speed overheating is insufficient waterflow through the system (plenty of airflow due to the car's motion).

How thoroughly were this engine block and cylinder head cleaned out during the rebuild, and how was that done? Over the years, a great deal of rusty mud can accumulate, and light-duty cleaning methods can leave an awful lot of it behind.

How sure are we that the exhaust system is free of restriction?

How sure are we that the water pump is a good one (can't be counted on with the poor quality of today's available parts)?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I've seen the "get hotter on the highway than running around in town" thing before and a new radiator always fixed that for me. (And a good thorough flush of the block at the same time for good measure)
One of the worst of those I've ever been around was my dad's old 86 van w/a 318....