I have a 79 Aspen Wagon with the 4-speed overdrive trans. I'm noticing that after about 20 mins or so at 70 to 75 mph the temp gauge starts rising. I recently bought the car and replaced a lot of parts that deteriorate over time. The cooling related items are as follows: I replaced the radiator, water pump, thermostat(new one is 195), hoses, and I even added an aftermarket gauge so I could have actual numbers as opposed to C or H. Now driving around town, at speeds below 55 the gauge shows the temp not getting hot enough to open the thermostat, but after I get up on the highway, it rises, albeit slowly, past 220. Whats a normal temp for this engine? Whats happening with my cooling system? I can't afford to blow it yet.

do a flush....

A SL6 should run at the thermostat temp.
The trouble with older engines is that they get a lot of rust, scale, "mud" that collects in the waterjackets. This "crap" will circulate thru the cooling system and get caught in the radiator, plugging the core tubes.
One way to check is to drain the radiator so you can see the tops of the tubes, if any have junk blocking their entry point, you have found the problem.
A good backflush can sometimes fix this issue but the proper fix is to mechanically clean the block, head and radiator.
DD

have you lost any fluid????????????? I had a very small crack in the head of one of my 6's ...........just enough to make steam and overheat..........you could not tell until I started checking the water level very closely. it lost very little and there was condensation in the tail pipe, or so I thought. It tasted sweet. ..........I didn't find it until I pulled the head and physically checked it............I hope it isn't the problem .........hope it's just slag. just one of those "it happened to me" scenarios.
best regards
max

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1966 barracuda 360
1964 signet conv. 170 turbo
Bonneville or Bust 2012

My truck had a similar temp rise at highway speeds.I did a flush and then it really started heating up.I believe someone used block sealer and the flush cleaned it out.Now it smokes heavily when started hot.The replacement head has cracks through exhaust seats into water passage in head.I hope you have better luck flushing the coolant than I did.

Crap in the cooling system can get stuck in the thermostat.

So at slow speeds it's opened to much (too cool), and at high speeds it's not opened enough (too hot)

For awhile mine was catching little particles that looked like sand. I'd just take out the thermostat, clean it, and reinstall.....

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

Thanks for all the input. This is where I'm getting confused. I've flushed the system, the radiator is brand new, and there is no fluid leak. I'm going to check the the thermostat to see if something is stuck. Thanks again.

you still might have a lot of junk in the system. When i replaced freezeplugs, i spent more time cleaning gunk out of the engine than i did cleanin gunk off the engine

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What's that fuzzy blue thing being hurled this way?
::stick::
BOOSH!!!

I learned early to never put a new or "recently serviced" radiator in front of an older engine with-out doing a complete cleaning of the engine's water jackets / cooling system... there can be a lot of "crud" build-up in there and it does not take long for some of it to plug-up a new radiator.
(The drain & inspect test noted above will tell you if that has happened)

I have to say that I have put clean radiators in front of old, rusty water jacket engines but I put a screen "trap" in the upper radiator hose, in order to catch the big chunks and keep those out of the "good" radiator's cores.

The problem with the screen is that it can quickly "load-up" and needs to be removed and cleaned / cleared frequently.
After seeing / cleaning the crud out the screen a few times, I "get around" to pulling the water pump, a rear freeze plug and the t-cover and do mechanical block cleaning / flush.
DD

I replaced a water pump, thermostat, thermostat housing, all the hoses, engine temp sensor, and did a full coolant flush chasing that problem . . . turned out it was really the gauge. Have you checked the actual engine temp with some type of thermometer? That'd be a place to start. I found a place that will recalibrate the factory gauge for about $27 if that's what you end up needing . . .

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1963 Dodge D100, SL6 and 3-on-the-tree.
1961 Dodge D200 Crew Cab, ex-USGOV, SL6 and NP435.

I've had thermostats go bad, so I always test (even a new one) on the stove in a pan of water before I install it. If your temp gauge is working OK (you can check it fairly easily by leaving the radiator cap off and using a cooking thermometer), the only thing that I can think of that would make a car run too cool is a bad thermostat. Lots of things can make it run hot, especially small leaks, so I always pressure test the system after I work on it before I button it up.

nottrndy,

Read this post Engine Cooling on page 2.

As Doc mentioned there is lots of junk in these engines when cast. When I rebuilt mine we dumped out 2 1/2 coffee cans of debris.

Not all stats react the same. I have several styles, with and with out poppet valves or built in holes, soup can style and flying saucer styles. Each brand and style has it own quirks in a stock slant with a stock radiator. I have quite a collection of them and find each one quite interesting when running an electric fan.

However, the 195 should keep you around 200 degrees unless you have a slight air leak, from a hose or head gasket letting air into the system creating steam bubbles. A new 16# coolant return type cap may help. Be sure it is sealing properly.......Hopefully your over flow coolant tank hose is not cracked and leaking. When working correctly it should keep the radiator completely full of water/anti-freeze with no air which allows steam pockets to create making the situation worse.

Is your anti-freeze mix correct?

Does yours have a clutch fan? Maybe it is shot and not pulling enough air through at higher speeds.

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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

Again thanks for the input. You guys are helping me double check myself. Here is where i stand. The flush happened before the new radiator and water pump went in. The cap was replaced as well with a 16# unit. Overflow hose as well as both upper and lower hose are new. Hopefully today I'll get around to pulling the thermostat back out to check it. I use the 50/50 premixed coolant. Its worked well for me in several past cars as well as my daily driver pickup. The clutch fan seams ok, but whats the best way to check it?

It does sound like a flow problem, but with the slue of new parts I hope it's not a head issue. I ran into the same issue with temp creeping up at speed and the fix was to unclog the radiator

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My '73 "Gold" Duster /6
http://www.cardomain.com/ride/2789359

With the engine off, just put your finger on the end of a blade and see how much slop there is in the bearing. It should feel very stiff and damped and resistant to movement, no slop or wiggle.
There are different types, some measure temp of the air flow and you find a bi-metal sensor on the front, others are based on rpm. Do you know which style you have?

Some other thoughts:

I still think you may have some air in the system causing the temp to climb when your loading the engine at higher speeds.

Is your temp gauge in good condition? If you ever over heat the temp senders they become very inaccurate. I swapped mine out for a new one the other day and was amazed how far the old one was off........It now reads per Dan's post on page 2.

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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