Make sure your radiator cap is the new style with rubber on both surfaces so it will draw water back in when the engine cools. The book says to run a 16 pound cap.
I have used 18 and 20 pound which really hold the temps down.
See if you can get that coolant recovery system working to minimize the the trapped air......it helps on the real hot days when the engine is working under a hard load......(lots of hills) and check your heater lines to be sure they are tight.

I suspect that the combination of parts your running between the block and head that some crap may be blocking somewhere....
When you pull the plug on the side of the block, does it drain out easily?

Don't loose heart...
Is the new radiator the 26" version? or another 22".

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I do actually have a 16 kicking around. I'll give it a shot.

The:

http://www.championradiators.com/plymou ... -1965-1966

is my radiator - the CC1635 22"

I will check the heater lines.

Yep, flushed the entire system last week, and the block plug flows real easy.

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

Are you sure the gauge is accurate?

Anyway to test with boiling water?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Are you sure the sender is the correct one for the gauge? I know a guy who fought the exact same issue with a '67 Valiant and it was the sender not matched to the gauge.

From the temps on your hoses I would say it is normal.

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Official Cookie and Mater Tormentor.

Based on your IR thermometer, you don't appear to actually be running hot. If that unit is OK, then no way you can read 180F on the tstat housing and actually be at 240F.

I vote for wrong/bad sender for gauge. If that's not it, thermostat would be next.

Lou

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Home of Slant6-powered fun machines since 1988

I'm with that, except for the fact that it's now been 2 gauges that are pinning either H and above (the first, old gauge), and 240 (the new gauge).

Also, my fans (which are programmed to come off at below 180) do NOT come off. Like, for 15-20 minutes or something.

Another question: could it be possible that one of the head - to - manifold studs could be blocking the water jacket? I ask because I have a really large stud in the last exhaust manifold only hole closest to the firewall.

I wish it was the gauge, believe me. But 2 gauges? Same problem? Different senders?

Hard to hate on the digital thermometer, though. Point it in my mouth and I get 95 degrees. That's pretty dang close.

One thing I can note: I did get one of those "tube temp gauges" as well, which unfortunately would only hook up to the block plug (not the best place for it, of course). It showed 180ish at the block plug (while I had it, those things are a bitch to work with, and it basically suffered a death by twisting).

I wish they made those tube ones with a sender small enough to put in the head. It would confirm or kill all overheating ideas immediately.

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

Well, for now, I'm gonna go with the thermometer reading. I've got no actual boilover signs to work with, and I do have to remember that the temp gauge is not stock.

Seems to me the area where it inserts (on the head at the front) would also pick up extraneous head temps as well, right? Maybe head temps that are adjusted for with the OEM sender/gauge?

Anyway. One more thing to try, but I believe I might actually be ok.

Thanks for the help, everyone. I'll update the thread once my final task is complete.

The message - don't trust a gauge until you trust the gauge.

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

The IR gun reports the average temps inside its sensing circle- which follows a cone-shape. So the closer the gun is to the surface, the smaller the cicle & more accurate the reading. Take some readings of the cylinder head at various points, esp near the temp sender - just don't get too close to the manifolds.

I'd also take readings of the upper & lower rad tanks to back up your hose temp readings. Then I'd crank the heater up for awhile & see if temps came down at all (ie, fans turn off).

If the eng temps ARE actually that high & you have a 40+* temp drop across the radiator then something's limiting coolant flow. (If an engine hits 240* & I shut it down- I usually expect to feel some "boiling" in the rad hoses because of the temp spike after coolant stops circulating)

You might want to do a quick voltage drop test on your ground circuits. With the engine running & rad fans on, use a voltmeter to check voltage from the alternator case to battery (-), and from both of those to body ground. You don't want more than .1-.2V or so (less is better). It's unlikely BUT I have seen V drops do weird things to (electrical) temp/ oil pressure gauge readings.

Besides causing overheat, a combustion leak usually shows up as loss of coolant with no visible leaks, engine misfire- esp on cold start do to coolant fouling the plug, or (heavy) white smoke out the tailpipe

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63 Valiant Wagon
225 - 4 bbl

So... uh, 4 critical words:

Get A GOOD GROUND!

Yep. Topping out at 210 on the gauge now. At most. I'm going to try a few things, as I feel like an even BETTER ground could change things more, but wow.

Oh, and another thing for overheaters: get a good IR Thermometer to double check everything. I have a MicroTemp MT-100 which I got on Amazon for $25. It's keychain-sized, and certainly (after this madness) it's $25 well spent!

Abandon thread!

At least for now. I've got some tweaks I'm going to do to make things better and more exact.

Thanks everybody!

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

Increasing the radiator cap pressure increases the temperature at which the coolant will boil over in the system since the "blowoff valve" (radiator cap) releases at a higher temperature. Running a radiator cap rated too low will allow the coolant to overflow the radiator not because the cooling system is malfunctioning but because the radiator cap is rated at the wrong pressure. Installing a higher rated cap won't change how well the cooling system cools, it will just change how long the malfunctioning cooling system will operate before the coolant boils over. Ideally the coolant will never reach the point that it will overflow the system when the correct pressure cap is used. Installing a cap rated higher than what the system was designed for is a band-aid to treat a symptom (overflowing radiator) rather than the problem (flaw in the cooling system).

Aggressive Ted wrote:
Ok, a little background...... the reason I went higher was two fold. The sealing surface on the radiator at the cap came some what deformed so it wasn't sealing very well with the normal Stant 16 pound cap. The coolant recovery system worked so-so for years with the stock 16 pound Stant. I really didn't notice any deformity when I got a new radiator from "Modine" or during radiator installation. However, it is very thin brass and easily deformed. Since then I have soldered the surface to build it up and fill in the deformities then filed and sanded the surface smooth and flat with a block type sander. When shopping for radiator caps I noticed that the 18 pound racing cap has much thicker and wider rubber seals and works like a charm. The coolant recover system works far better than when the car was new. So look for 16 pound caps with nice thick rubber seals if your having trouble with your coolant recover system.
The two rubber seals in the new caps all seem to thin and wear out to quick for me. You may want to check out the heavy duty racing caps.

When using the two 10" electric fans......I still like running the high flow thermostats and the 18 pound racing cap as it keeps the temps down on 90+ degree days to where the fans rarely come on and when they do, do not stay on very long even when giving the engine a good work out with the car loaded going over the mountain passes at 70+ mph.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I can see switching caps for a better sealing area, but unless you are accidentally running a cap rated below what the system was designed for, switching to a higher pressure cap won't fix anything. It may actually cause hoses and other seals to blow out if you do have a real overheating problem.

I agree with Reed. A higher pressure cap puts more pressure on all the components. One of the benefits of running the Evans coolant is that you use a 7 lb cap, because the stuff boils at such a high temp, which you never would reach in operation, there is very little expansion of the coolant. This reduces the strain on the entire system considerably. Putting the lower temp thermostat in reduced the temp of the coolant, while still pulling the same amount of heat out of the engine. Or so they say. Anyway, so far so good.

63Valconvert, good news on the ground issue, and WagonsRcool, good detective work there. 63, I would proceed to run those voltage drop checks all through your electrical system. You may end bypassing the ammeter as many of us have done. That and the bulkhead connector can be major sources of resistance in a system that was marginal to begin with.

I have replaced all the wiring in my car one wire at a time.

Sam

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This can only be a hugely great idea. I'll get started with this. I've always wondered about working with changing up wiring, especially since a buddy of mine in Canada once lost his 69 Dart to a wiring fire!

Thanks for the advice.

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

Here's another reason to fix the ground circuit; excessive voltage drops on the ground side will cause the the lil 'ol electrons to find another way home- thru the coolant. The result is called electrolysis, where the coolant additives break down VERY quickly & all the cooling system parts corrode & fail. Heater core, radiator, water pump, casting plugs, HOSES- it all can be degraded.

So clean the negative cable ends & add several redundant ground leads from battery to engine to body.

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63 Valiant Wagon
225 - 4 bbl