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overheating in traffic any ideas

magvan

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this in in my 1974 B body van with a 318 2 barrel engine.
i have been messing with this overheating problem over the past year and have yet to figure it out.

the engine is the original 318 2 barrel, it stays cool around town and going down the highway. When i get stuck in traffic it starts heating up. it had the original fixed blade fan (no clutch) and radiator with shroud.

i replaced the original thermostat with another 180° one, it made no difference.

my plan is to install a 440 in this van so since i had everything sitting here i went ahead and installed the 440 radiator and shroud. i used the fixed 6 blade from a 1969 383 engine.

it runs cool around town and going down the highway about 180-190° but if i sit in traffic for 5 min it starts creeping up ive seen it as high as 240°

could this be a water pump issue?
 
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heating up while sitting still is almost always an air flow issue.do you have a pic of the new setup?could be a shroud problem.how close to the rad is the fan?
 
Put a aluminum radiator in it. That cured my issue. My Duster did the same thing.
 
If your van came with factory A/C (you have a shroud on the radiator so I believe it did) make sure you have a 26/28 inch radiator in there.. Verify the part number for the van.make sure this is right..2nd check the radiator cap... if the pressure is wrong or the cap won't hold the right pressure... you're going to overheat.... 3rd... Make sure you have an a/c water pump installed. You'd be surprised how many parts stores will sell you the wrong water pump... it makes a difference.... 4th Make sure the mix on your anti-freeze is 50/50 and the level is right in the radiator/overflow tank.... 5th...check your oil... when you change it is it orange/frothy??? a blown headgasket or even a tiny headgasket leak can do this to you..... but you should see it in your oil.... it takes very very little coolant in oil to get it to change color... check it anyway...6th... is your Van supposed to have a fan clutch installed? Most A/C cars/trucks use a clutch of some sort...

Finally, any combination of the above will conspire to frustrate the life out of you.
You might want to drain the coolant and take a look at it... it could be that your radiator just needs to be replaced.... Best of luck to you
 
bet its a fan clutch. oops reread that its fixed
 
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no A/C but it did have a shroud on the original radiator and there is a shroud on the big block radiator that is in it now.
Yes it is the big 26/28" radiator. i had to change the core support etc in order to install the larger radiator
the radiator cap is 16lbs. What should it be?
i dont know what water pump is in the engine. is the A/C pump the 6 or 8 vane type?
the coolant is 50/50 and less than 6 months old
the van never came with a overflow bottle, but i did add one when i installed the larger radiator, and the level is good
the oil looks & feels great and is the correct engine oil color
the van originally had no fan clutch, the larger fan i installed also has no fan clutch.
i doubt that the radiator need replacing as it had the same problem with 2 different radiators

- - - Updated - - -

Is it hard to start after letting it sit a few minutes and trying to restart?

engine starts right up, i mean, i barely have to kit the key and its running. not even one full crank. i wish my coronet started like that
 
Fan shroud makes a big difference... my 67 coronet has A/C fixed fan and shroud. Unless you test a thermostat in boiling water when it operates who knows... I rejected way to many new ones for opening late... I drill a 1/8" hole in them also to help bleed the air out of the intake
 
I had issues with my 440 heating up in my 65 plymouth satillite last summer so I decided to get serious about fixing the problem. Brand new rebuilt motor heated up to 220/230 degrees after about 10 miles of driving. It turns out the motor mounts on the car was homemade and way off of position where it should be. I bought some schumacher motor mounts changed the smaller fan for a 7 blade 19" steel chrystler one I got in a salvage yard, had it powder coated installed that. The new mounts moved the motor forward about 1 3/4" down 3/4" and to the passengers side about 3/4" Wow! so now its within 1/2" of the radiator, fan is right inside the shroud where it should be and now runs at 180 degrees and hopefully will stay there in the hot summer days. Good luck with yours and don't get discouraged
 
Can try an electric 14" pusher fan on a temp activated relay, $30 bucks at parts house. so it will only come on around 200 and run until its under that. I run one on my 493 180° stat.
 
mag, you didnt say if you have measured the gap between the rad and the fan yet...that will make a big difference if it's too far away, it wont pull the air thru the rad enough to cool it. Me thinks with a new core support, that may be your problem

btw, 16 lb i believe is right for a 26" rad. that's what i have on mine anyways lol
 
Just had an issue with my truck, 64' D200 CSS, and as it turned out the non ac water pump pulley was too big in diameter, swapped to an ac pulley, ac water pump, and clutch style fan.....bingo, truck runs about 190 and it doesn't have a shroud, also a 180 t-stat.
 
It is possible for this to be a water pump issue but that is rather rare. Take the pump off and see if the back of the impeller is close to the back of the water housing, and that the impeller is hard locked to the pump's shaft.

Is this a used radiator? If so, you need to get it to a rad shop and have it cleaned out. That is the most common problem. Flush the block properly before you take the rad off for cleaning.

If the fan is sitting within the shroud in it's normal place, then that is not likely the issue.

If that is OK, then you may have a head gasket leak; that will allow hot combustion gases into the coolant jacket. Cracks in the heads and block will do the same thing. No matter how new the rad, the coolant, or the water pump, it will eventualy overheat from this. Get a rad system pressure guage and use it to test if you can pressurize the colling system to 15 psi or so, and see if it will hold the pressure. If it leaks down, and you can't see an external leak, then it is leaking on the inside. The guage can also be left on while the engine is idling, and you can see how high the pressure goes; pulsing on the pressure guage is a sign of a combustion leak.

A rad shop can do this for you if you cannot borrow a pressure guage or don't feel confident.
If that is the case, check your plugs and see if one has some very fine, whitish granular deposits on the plup tips. If so, that cylinder is taking coolant.

Just an FYI: there are a number of issues that can cause your problem. You are going to have to start doing some tests and checks. Do these tests and steps before you start throwing parts at it or you may just waste your money.
 
Sounds like airflow to me. Couple of measurements to keep in mind - fan should have 1/2" to 1" clearance between blade and shroud. Also, blades should be about 1/2 in / 1/2 out of the shroud to maximize airflow. A fan that is too far in actually pulls far less air, as about 1/2 of the airflow comes off the tips rather than through the fan.

The other thing to consider is scale in the block. Flush it out and see what comes out.

Also, maybe not an issue for you but timing makes a difference too - too retarded (or not advanced enough) creates a lot more heat.

All those issues conspired to make my car do the same as your van.
 
Sounds like crud in the radiator. Pull the block plugs on each side and see what comes out... fill with water and flush a half a dozen times and be careful the flush doesn't loosen up leaks... some idiots will pack the cooling system full of stop leak and make a mess out of it.
 
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