Overheating FAST

Post by **HellBelly** » Mon Mar 29, 2004 1:15 pm

I have 1974 /6 in my truck.

My radiator has been leaking for some time now, but I just add water to it and keep going. No biggie, I don't have the 200.00+ dollars to get another one so I've been dealing with the leaks. I patched a few but it would just spring more.

Anyway here is goes:

There are 4 lines on a 71 temp gauge. 1st line is the beginning of the gauge. 2nd line is the beginning of the reading area. 3rd line is the end of the reading area. 4th line is the end of the gauge.

In the morning I will start the truck and warm it up and it will get to the second line when I take off. I will drive it about 3-4 miles and the gauge will shoot all the way over to the RIGHT to the third line. I've stopped before and the engine doesn't seem that hot to be all the way over to the third line. Once I hit the high way and start running at about 50-60mph it starts creeping over to the 4th line and then PAST the fourth line. IF I don't slow down or stop driving it, it will eventually blow the upper radiator hose or just flat out overheat and blow more holes in the radiator.

I'm tired of having to worry about this truck over heating all the time when I take it on long trip where I'm running 50-60mph for more than an hour.

It had a 160 thermostat in it, I replaced that with a 180 thermostat. That made no difference.

It has a Flex fan on it, but I've heard the flex fan is no good at highway speeds, it flattens out and doesn't draw air? Any truth to that?

Any of you guys running a fan shroud? My truck doesn't have a fan shroud at all. My 65 never had one either, so I don't think that's it.

Water pump isn't leaking? But there appears to be no water flowing in the radiator? Could the pump be bad? Even when it over heated yesterday on the way back from the camping, I filled the radiator up and the engine was scorching hot, and when the water finally got to the top of the radiator it was still.. Wasn't even flowing and the gauge was reading all the way to the Third Line still. If should have been flowing?!

Any advice would be helpful.

Post by **Hobcobble** » Mon Mar 29, 2004 3:50 pm

Scott,
The vertical core rads can plug up on bottom when they get old. If you
have made a few repairs, chances are that you're not getting sufficient
flow. These old rads are designed for use with a 7psi cap and if you're
running a 15 to 20psi cap, this can raise h*ll too. If it were me, I'd re-core
the rad. Since you'll have the motor drained, you might want to replace
the water pump and replace hoses & clamps too. The way that the gauge
is drastically jumping can also sometimes indicate a voltage limiter
problem. I don't know much about flex fans... but if you could find a
stock fan with 6 to 8 blades and install it, this may help also. Do you still
have the rubber core-to rad shroud on your truck???.... this small strip
of rubber keeps air from flowing over the top of the rad and pushes it
into the cores. You may also want to pop a couple of lower block soft
plugs out to see if there's a serious crud build-up.... Finally, I would
recommend a good mechanical temperature gauge.
John

Website · Post by **wideblock** » Mon Mar 29, 2004 6:11 pm

scott, sounds to me like your new thermostat is sticking. did you get the high flow, or the regular old off the self modle? i have a good rad on the parts truck if the hoses are in the right place for your 6 ill cut you a good deal. by the way, it only cost me a shade over $80 to get mine rodded out and patched up at a shop, beats the hell out of the price of a new one. you might try a good old fashioned back wash of the rad and see if it helps any. like john said, the verticles tend to plug up at the bottom, especially if its been running dirty water for a while, stick the hose in the top, wrap a rag around it so it cant leak, pop the bottom hose and put the hose on full blast, see if it blows out any crud that might be built up. as far as the flex fan flattening, yes they do flatten at higher rpms. but at freeway speeds, you should have more then enough air moving thru that grill to keep it cool even without a fan. if you need the stretch of rubber that goes between the rad and the core support, let me know, i got one of them too. without this piece, the air flows over the rad, and not thru it. i havent seen a swept yet that had an actuall fan shroud, how close is your flex fan to the rad? mines only about 1/4 inch from the rad, if the gap is too large, then you wont draw the air thru as you should. by the way, if the poly has the same bolt pattern, i got a fan too.

Post by **oneowner71** » Mon Mar 29, 2004 10:15 pm

Well, Trey, I guess I will have to come visit you. My 71 has a fan shroud, and the Dude has one somewhere??.. The 71 is running a direct drive fan (no clutch 5 blade steel). What I got from your story Scott is that the truck was overheated, but you still had the radiator open and adding water... did I read something wrong. If thats the case, then I would say you aren't getting very good water movement as the water in the radiator should be stinking hot too. I have heard that sometimes the impellers on the water pumps will fail without the seal leaking... may be something to think about, but I would lean to a plug somewhere in the rad. I have the 180 deg therm in mine without that little rubber strip at the top and it runs a pretty constant 205 to 210 degs regardless of speed, load, or traffic.

MountainMoparRobin · Post by **MountainMoparRobin** » Mon Mar 29, 2004 10:40 pm

Trey
if you look at the pictures of my engine compartment I've always had a fan shroud, I tend to agree with both trey and hobblcobble I think ya have a thermostat that isn't working and if I was still in Texas I would have the 160 thermostat, (which I always have in my vehicles anyway) anything above that when your driving in temperatures of 95 and heat index of 110 doesn't leave ya much time to catch it from overheating! I think Hobble cobble also has a point about your radiator not allowing enough flow, definitly keep your eyes open for a fan shroud makes a hell of a lot of difference! I can feel my fan sucking air through the grill at idle! I believe they have said the flex fan isn't good at high speeds! :roll:

Website · Post by **wideblock** » Mon Mar 29, 2004 11:27 pm

hey hellbelly, why not an electric fan? i installed one on my bosses mustake a month or so back. had a temp sensor and all, you set the temp it comes on at, and goes off at. had a built in shroud that took very little mods to make fit perfect. best thing of all, you free up aprox. 7hp not spinning a fan manually. with that /6 you need all the help you can get. and i disagree with robin, 180 is the best stat to run, 160 is too low. i could explain, but it would take too long. maybe some other time when im not so tired.

Website · Post by **wideblock** » Mon Mar 29, 2004 11:37 pm

did you happen to put the new thermostat on top of the new gasket rather then under it? i know this may be a stupid question, and im not doubting your intelligence. but i have done it on accident my self, and it makes the stat not open all the way due to the gasket being in the way. just a thought, i mean you do wear shorts while weedeating, so you have done more odd things then that.

Post by **cowboy** » Tue Mar 30, 2004 9:34 am

I will agree with most of what you guys said , but like Robin , I have always run the 160 on these older trucks , 180 on the newer ones (70's) with the older Raderters not much room for arier in overheating , & what rubber piece are you talking about ? Scott I now have a extra fan should, email me for more info , or if you can aford it check into the elec fan deal they are a lot more efichent (sp)
8)

Post by **HellBelly** » Tue Mar 30, 2004 10:06 am

Guys I really appreciate all the feed back. This is the reason why this website does so well. We have some the best guys here. Your knowledge and kindness/respect for the stupid questions makes people more comfortable. I appreciate that and so do other that visit!

I now have some things to check on, I definitely want a fan shroud and a new radiator if I can swing it $$ wise. I like the electric fan idea also. Where could one check on prices for one?

Trey, I need to import that finger smiley over here, just for that weed eater comment!! I need to get a picture of my leg before it totally heals. It's looking much better.

Post by **Hobcobble** » Tue Mar 30, 2004 4:05 pm

Cowboy,
I'm talking about the strip of rubber that clips onto the core support
and lays over the top of the radiator. Without this, a lot of the incoming
air will pass over the top of the rad instead of going towards the cores.
It clips to the top of the support ["s" clips] and to the sides of the
radiator bracket. The strip is about 4" wide and has a notch for fitting
around the cap.
John

Website · Post by **wideblock** » Tue Mar 30, 2004 6:11 pm

hey, if you import the finger smiley, be fair and leave it for everyone to use. thats about all i miss from the old site, it had a much better smiley selection. as far as getting a price on the elect fan, check the local speed shop, thats where we got the boss mans. autozone sells them too, as does napa. you can get anything from a simple toggle on and off all the way to a dash mounted control panel, depends on the money you want to spend. its funny in a way, you got 4 trucks, and not a good rad between them?? and you still didnt answer where you put the tstat gasket. over or under the tstat?? and to add to the other comments about your water pump, over time corrosion can eat away the impellers, or build up on them making them far less efficient. if you go thru the water pump change, go for a flow cooler, they are worth the extra money.

Post by **cowboy** » Tue Mar 30, 2004 9:32 pm

hobcobble thanks , it's been so long since I've seen one , hey scott can you hobble over to the old site & bring over all the smileys? :roll: :P
8)

scoutski · Post by **scoutski** » Wed Mar 31, 2004 7:51 am

Hey Scott, Have you checked the lower radiator hose. I had one that would go flat when at higher RPM's and cause it to overheat.
just my 2 pennys,
Bill

Post by **cowboy** » Sun Apr 04, 2004 8:29 am

man getting old, I forget about that , thanks Bill , scott the lower hose should have a spring in it
8)

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