Sorry, I would never normally post such a lame question but this one has got me stumped since ive tried everything I can think of and everything that everybody else has suggested (even If had already done it once on my one ,LOL) Stock rebuild done on an early 80s vintage 318. mild cam (summits mildest grind), valve job, hone and rering, w/ all new bearings. This setup would get hot while sitting at a light before any of this work was even done. So to make sure I fixed it, A brand new alum rad was used (4 core I believe) for a '65 mustang. Hoping that would be overkill I dint think twice about using a crappy rigid bladed flex fan (the really angular shaped one), and no shroud. first time I hit traffic, I installed a shroud the next day. now the temps are staying at 160-170 for a 2 hr trip cruising at 70 mph. As soon as I hit the traffic at the Syracuse nationals, the temp slowly start rising and pegs on ''H" well before I get to a parking spot. As soon as I shut it down Im greeted to a terrific boil over :-( off to the vendor area I go to purchase two 8" fans, some wiring and some jumper clamps. I "hot" wired them on and the next day I stilled pegged the needle but avoided the boil over (pegged is about 205-210) The entire ride home (2 hrs @ 70 mph) the needle was right about 160-170. So as long as Im moving its good Even in the garage idling, w/ the hood open, the temp will slowly keep rising over 205 (then I would shut it down) So I extend the shroud all the way to the crossmember. Search high and low for a fan that would fit w/ a much more aggressive pitch (came up w/ a 17" 4 blade that's got a lot of pitch to it). made a new smaller Vgroove pulley that will over drive the pump and fan (only about 5%) Timing was also double checked and is at about 12* Also replaced the upper rad hose since an ol timer noticed it goose necked higher than the rads top tank and may be trapping air. (still odd even after swapping it, If I shoot that hose w/ the temp gun it is 20-40 degrees cooler near the tank ,is that normal?) I also tried a 180 Tstat, and threw on a makeshift recovery tank just to see if any of that would help. at idle , it still keeps creeping up till I kill it at 205. By the way, that new fan /pulley/ shroud, sounds like a Boeing 747 its moving sooo much air . Heres some current pics to show what Im working w/. Im open to try anything! (I havnt done a new water pump since its clearly pumping , but should I just throw a new pump at it just to say I did?) also threw together some air dams to be sure the fans drawing fresh air from the grill area and not just recirculating the underhood air.. I left the two 8" fans on just to give alittle extra support if needed (toggle switched only), but they really don't seem to help. sorry, so long winded, just wanted to give the whole story all at once. This is a stock 318!, it should not be giving me overheating problems thanks, Jeff
2 overlooked causes of overheating, spark timing way off, exhaust restricted. I doubt those are your problem just throwing it out there. 205 isn't that high, if you have a 16 pound cap it shouldn't boil over till it hits 240. Cool on the hiway hot in traffic usually means rad is plugged up or too small, or not enough air flow but those do not seem to be it.
Waterpump not circulating at idle, extremely lean condition (idle), or leak in the cooling system thus not pressurised properly?
When you are driving air is flowing through all of the radiator, it looks like the way you fabricated the shrould that you arent using the upper corners of the radiator if your sitting still, the fan will only pull air through the round shroud. If it runs cool driving and gets hot sitting still that is usually an airflow problem, not a capacity problem.
The water pump is the wild card and may just be marginal enough to keep it cool at a cruise. I would change that since its cheap and quick to do.
Thermostat in the 180-195 range shouldn't cause a problem & probably should be used. Yeah, looks like you need to seal all the open space around the shroud so the fan pulls air through all of the radiator. Any idea how much overbore was done?
Thanks for taking the time to add to this guys. W/ the rad cap off I was able to confirm that the pump is circulating at idle. I really don't know how to check to see if its extremely lean at idle but that thought has crossed my mind. The carbs an edlebrock 4 bbl and I adjust the idle mixtrure screws using a vacuum gauge to achieve the highest reading. (it does however hunt around a small amount at idle, and this could be a symptom of lean) Would it be asking too much to expect a 318 to be able to maintain 160? (im new to the 318's) I didn't realize (until I just looked at the pics I posted) how much of the upper corners are not included in the shroud. I should be able to add in some blue painters tape to seal these up and test this as an issue. As for the overbore, none. everything checked out great so all it got was a quick hone and then re-ringed. No, I never thought that could be an issue. Could a cap cause the temps to just keep rising while at idle? Off to the garage to tape up the shroud and swap rad caps. keep the ideas coming! Jeff
Put a paper towel on the front side of radiator w/motor running at about 2000 rpm, it should stay put down to approx 1400, if not your having air flow issues, that shroud looks like it has many places to draw air from places you don't want. I have always tried to keep the fan blades half in half out. Also noticed that those pusher fans are mounted via wire ties thru the core, not a good long term condition. The fans will eventually vibrate enough to cause a leak, know by experience.
JUST found something! I went and did a quick tape job around the shroud and as I was feeling around the grill opening w/ the car running I could feel hot air at the lower corners of the rad and it was blowing OUT! It seems im pushing so much air into the engine bay, its looking for any nook and cranny to get out. So I went around and sealed up the edges. Also if you stick your hand under the front bumper and start reaching towards the crossmember, theres so much hot air blowing forward it heating up the splash pan in traffic, that will definitely not help. But heres the big find. (but what is it?) as I was feeling the front of the rad, I noticed the upper drivers side didn't have much if any air being pulled thru it. In fact, it felt like it was radiating heat towards the front? So I tear off a pc of paper to check the airflow in that corner and look at this! The airs blowing OUT!! where my finger is holding the paper, theres enough suction "in", in that spot that the paper would stick on that end and blow straight out on the other. WTF! lol so now intsead of cooling the rad, im heating it the only thing I can think of is the alternator is inside the shroud and in that upper corner. Do alts blow forward? Its a GM one wire . huh? jeff
Well I'd say it's an airflow problem, the shroud needs to be tighter to the tips of the fan blade to be effective and also it needs to cover the whole fin area of the radiator and funnel the air through the fan. I have a similar problem with the 318 in my 46 plymouth, the little 4 blade fan doesn't move enough air at idle and will start to run hot when sitting in traffic, running the engine at a fast idle helps a little
Didn't pay attention to that, a fan with more blades would/should be an improvement. Your engine would do better with the 180-195 thermostat & I believe the OEM one is in that range. The higher the lb rating on the cap the hotter the water can be w/o boiling. Heard the Northstar thermostat is over 200, haven't heard what pressure cap they run.
More to the point, why?? Efficiency drops off radically below about 180, raw fuel starts dumping into the cylinders because they are too cool, and excessive wear starts. There is a reason no car specifies a 160 degree thermostat, the engineers know what they are on about. An engine is a heat pump, allow it to pump heat, and you will be happier. Cosmo
Fan is the problem. I had a 4 blade on my dodge and it would start to over heat a a stop light. I found a fan off a poly 318 and it helped a lot. Posted using the Full Custom H.A.M.B. App!
All good points about the 4 blade fans and the 160 tstat. the fan is in a super tight spot so while trying to find one to fit this aggressively pitched 4 blade came up at the best option, and gotta say that im pretty sure its not the problem since it moves ALOT of air. As for the t stat, I will probably go back to the 180 the next time I have to drain the coolant. Although I admit, since the temp does creep up at a stop, I do like that extra 20* buffer. No one commented on the latest discovery that hot air is blowing out threw the rad in one corner. That's where my attention is going today ( got the day off of work, yay!), Im going to shorten and rework the shape of the shroud and try to get the alternator out of the shrouded area. cool air good hot air bad. jeff
The round part of the shroud doesn't need to go beyond the back of the fan, if you trim that hopefully that would get the alt out of the shroud, or make the circle part smaller diameter & shorter to get the alt out of the situation (if that's why it's "pushing"). If all is "well" with your cooling system you should be able to drive anywhere with a 195 thermostat w/o problems. Thermostat: It's not really a 20 deg cushion, it's too cold a setting . Cyl wall wear is reportedly 3 times greater with a 160 than with one in the 180-195 range. I believe all of this 160 thermostat stuff started with 90s Mustangs (possibly other computer controlled stuff) that the 160 would "trick' the computer into dumping more gas into the system when drag racing, improving times a bit. Not a good thing to be doing on street cars
You don't have a 20 degree buffer. The thermostat can only hold temp if the cooling system can hold temp. If the temps creep up at idle, you have an airflow problem. I experienced something like this when I went from a two row to a three row radiator in my Falcon. It's harder to get air through more cores, so the temp will rise at idle due to lower air flow. Make sure the air can get OUT of the engine compartment, which seems to be a problem if the air is trying to exit forward. Cosmo
Very much agreed. I've seen the same with the Jeep guys, which I "fixed" with a resistor in the temp sensing line, instead of a 160 'stat, which fooled the computer while allowing the engine to operate at a reasonable 195 degrees. Cosmo
Post # 9 addressed the issue. Turbulance inside the shroud cavity will send the air the opposite way. Did duct design for years and we found when we used a square elbow the air would hit the backside and a certain amount would come right back so in the process of balancing the air to each zone we would come up short. So we used radiused elbows from that point forth. As you are doing now redesign the shroud with the fan blades half in and create a funnel type appearance to the shroud covering all the core of radiator. This will help quite abit towards your in traffic cooling issues, but if there are other issues they will have to be resolved also
And its help like this that made me post a lame over heating problem on here. Some of the locals are helpful, but do you know how many of them told me I had to remove the Tstat, LOL the knowledge and experience here is top notch! The 180 is back in and im banging out o a new shroud right now. jeff
The lower temp thermostat can actually make the car run hotter, so don't think that just because you put a 160 thermostat in that it will run cooler. The idea being that if the 180 stat closes, it will trap the water in the radiator longer, where it can be cooled further before the thermostat reopens and allows the cooler water into the engine. If the thermostat stays open because the operating temp is lower, the water in the radiator may not stay there long enough to be sufficiently cooled before returning to the engine to be reheated again. My car ran almost 200 degrees with a 160 stat in it, but runs 180 with a 180 stat. Other tricks you should consider: -A larger fan with more blades. I run a 7 blade fan out of a 70 Eldorado on my engine. It's like a damn tornado under the hood. -The idea of a fan shroud is to pull air through the ENTIRE radiator, even the corners not covered by the fan. The shroud should encompass the entire area of the core, and fit the fan to a half inch or so, with the blades about half in the shroud. That way the air drawn by the fan pulls through the whole radiator and increases efficiency. -Add some water wetter. Seriously. It works. It will reduce the surface tension of the coolant and your temps will drop. Also, in the non-winter months, run a higher percentage of water to antifreeze. Water cools more effectively than gycol based coolant.
BTW, I just checked out your build thread. That is probably the nicest looking Plymouth of those years I've ever seen. They're a real challenge to get right, and you did it. Even Barris screwed it up. You have one hell of a nice looking ride. As much as I hate to break it to you, if you're having an air flow issue, you may just need to move the radiator forward to accommodate a larger mechanical fan and shroud. The two electric pushers are really just a band-aid solution, since they're unsightly, a pusher fan is less efficient than a puller, and the motors on those electric fans are creating a dead zone on your radiator for air flowing in. That 4 blade fan you have on there is junk for what you need it to do. Upgrading to a bigger fan to increase air flow and a proper shroud will be the ticket. I've been in your shoes before.
Water sitting still in a radiator will not cool off faster or very well for that matter, than water that is moving. In order for heat to transfer effectively, it needs to stay moving, "scrubbing" the walls of the radiator tubes. Standing water, or slow moving water through a coil/radiator inhibits the heat transfer effect. For most efficient cooling, you want constant and high flow rates through the rad.
One aspect that has been touched on but not explored is reduced flow inside the radiator - If you put a new radiator in front of an older engine there is a possibility that scale/rust/gunge can be dislodged from the engine and block the tubes on the new radiator reducing the rate of flow and thus over heating - ask me why I know - happened to me on a new radiator three years ago and two years late the top tank was off for the tubes to be cleaned. Solved the problem by putting a filter in the top radiator hose to catch the debris before it entered the radiator
good point 35desoto, I did flush the block out real good when I had It apart for the rebuild. Freeze plugs out and scraped and pressure washed all I could reach and see. But, after the boil over in Syracuse I did notice some sediment in the coolant and the coolant had a brown tint to it. I immediately pulled the rad and flushed it from the bottom to the top and then top to bottom all while shaking the piss out of it, LOL. I also ran the car w/ a garden hose feeding the water pump and did this until clean clear water flowed from the upper hose (rad was still out of the car). coolant may still show signs of a little sediment in it but not bad at all. What did you use for a filter? new shroud is coming out pretty good and will be a definite improvement, once its done. jeff
Yeah, as far as shrouds go that one leaves a lot to be desired...but it's understandable because a good one can be a real time consumer to fabricate! You need a box that seals well to the 4 sides of the rad and a hole/tunnel that fits the fan well. Try to imagine a spinning fan with no tunnel. The blades move air to the rear but also have a lot of air slipping off the blades parallel to the blades. (Radial flow I guess...) Without a tight fit to the tunnel this air can disrupt the flow thru the fan and reduce how well it works. Even free standing electric radiator fans use a flat ring that joins all the blades together, for strength no doubt, but also to prevent that backwash of air off the blade tips. Almost like a built in tunnel. IIRC, a properly located fan has like 1/3 of the back of the blades outside the tunnel to make sure any of this radial backwash has an easy path in the right direction and thus increase the flow thru the rad.
I'd make a map of the temperatures measured on the face of the radiator with the engine idling when the temp has climbed pretty high. The map should include at least 16 measurement points spread evenly across the radiator face. I'd use them to judge if the radiator is receiving hot water and successfully cooling. Beware of infrared laser aime temp guns. The color/finish/material of the surface being measured can make a big difference in the temp diplayed. While the temp gun is out I'd shoot the engine exterior for hot spots and uniformity. A good radiator being fed a good flow of HOT coolant should be HOT at the inlet tank, many degrees ( 30 plus maybe ? . Check the Daily Driver for representative temps )cooler at the outlet tank, with a fairly uniform gradient end to end ( or top to bottom with a downflow rad) and no cool spots. If inlet and outlet tanks are similar temps then I'd say the airflow thru the rad is too low.
This may sound silly but my radiator man said to insert the foot end off a pair of pantyhose in the top of the radiator and fold them over the in pipe to form a sieve and it works - I am sure someone will pipe in with something more exotic or a proper part however this simple application proved to me how much scale was circulating in the system despite me being care full with anti-freeze solutions. The point mentioned over checking the temp of the core all over is a good issue too - the whole radiator should be warm and not just in a couple of places - while the temp will vary slightly over the whole width there should not be "cool" spots - this indicates the tubes are not working. I cant speak over a Mustang radiator but an original MOPAR radiator of the 60's or 70's had excessive capacity so you could loose an amount of cooling capacity and not notice the decline.
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