Hello Everyone,

I have a home built roadster that I'm working the bugs out due to the previous owner. Its a late 60s 225 with a 904. The car weighs 1600lbs and has a small trans cooler mounted in front of the radiator. The radiator is a 14"x14" mishimoto 3 row aluminum radiator. Stant 180 thermostat. I'm using a 12" electric fan that's mounted directly to the rear of the radiator. I installed a temp gauge right behind the thermostat in the stock hole. While cruising around 40mph the gauge says 220-235 F this is with the electric fan running non stop. This Saturday I will be building an aluminum shroud for the fan so it draws air through the whole radiator hoping that will help. I flushed the engine with a garden hose and nozzle to add some pressure. Also flushed the radiator too. Timing is set at about 10 BTDC I believe and I recently adjusted the points.

Any other ideas to help bring the temp back down to normal operating temps? I assume normal for a slant is 210? After I install the shroud if the temp is still high I may switch to a smaller trans cooler in front of the radiator. I would have mounted it somewhere else but there isn't much room under this car as it is a 1927 ford model T body. A friend of mine suggested using Evan's Waterless coolant, is it worth it?

Any help is appreciated! Let me know what other details you would need.

Not with a 180F thermostat. My vehicles run at 185-190 with a 180F

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

An external trans cooler in a 1600 lb car is probably over kill unless you pull a car hauler trailer with that rig.

The stock radiator for an A Body is about the same size as your radiator, and an A Body is about twice the weight of yours, and probably has more frontal area to slip through the air. In other words engine is working harder and producing more heat than the roadster would.

Is there good coolant flow through the radiator? Is the lower radiator hose old and soft and collapsing at higher rpm? If flow is poor both situations would indicate partial blockage of the radiator.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I wonder if you have flow/blockage problems in the engine? I would think that would be fine with that rad and setup. I would skip the Evans. I bought a car with Evans once. If you have a leak you can't replenish with water or trad'l coolant. I swapped it to regular coolant after it leaked out enough of the Evans to cause it to almost overheat.

Try pulling the t'stat out altogether and see how hot it runs. If cool w/no stat, the maybe it was in backwards or stuck/faulty. There is a myth that no stat will make it run hotter, but that has not been the case with any of my Slants - several experiments done...

Lou

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Home of Slant6-powered fun machines since 1988

I figured I didn't need a trans cooler since it was such a light car that may only haul a lightweight 5'x3' hot rod trailer once a year but everyone on here said I'd be crazy not to run one. The lower hose has the spring and when idling I have not seen it collapsing. I can try to place a camera on it or have a passenger watch it while driving. What would be a good way to test flow through the radiator?

Originally when I purchased the car the t stat was in backwards. Currently I installed a new stant that I tested and is opening and its in the correct way. Before I was just draining the block via the radiator hoses and flushing with a garden hose through the t stat housing. I flushed the engine and trans till it ran clear and drove it around with new fluid for a little while. Then when I started having problems again I flushed both rad and block till clear and still having issues. Should I pull the plug on the passenger side of the plug and see what comes out there?

Not a bad idea to pull the block drain. I assume your access to it in a roadster is much better than it would be in an A-body. Be prepared to extract that plug in non-traditional ways if it's never been removed before. It's a standard size if you need to replace it; 3/8" NPT if I recall right.

Is there any reason he couldn't test for hose collapse at high RPM with the car in Park? That would be easier to check.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

I like running it with the thermostat removed as a first troubleshooting step: the easiest.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Thanks for the heads up on the plug size! I will open that up and see what comes out. Then check the points gap and remove the thermostat and see what happens. Once its up to temp I can recheck the timing. If no big change after the above test I will remove the trans cooler and see if that makes a difference. Don't want o change too much at once and not learn where the problem was.

If you remove the radiator cap can you see straight down into the core or is it on a neck?
If you can see into the radiator you can look for traces of sediment in the top tank.
Then leave the cap off from a cold start and watch for good flow, either immediately with the t-stat removed or once it warms up with a t-stat in (maybe siphon out a pint or so to keep it from overflowing as it warms up).
Have you visually checked the pump impeller fins?
You mentioned that you flushed the radiator, but if you have a big sediment problem you may need to remove it and back flush it upside down.

Also, use an IR thermometer to take readings all across the core and various points on the block, looking for 'cold where it should be warm' (clogged tubes?), unexpected hot spots, or any other anomalous readings.

The trans cooler shouldn't be adding enough heat to the air stream to have this much of an effect, so I wouldn't worry about that just yet.
Properly sized and functioning radiators work just fine behind A/C condensers and trans coolers in closed engine compartments all the time.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

good news I found a way to get the plug out without messing it up. I used a 3/8" drive extension backwards like a socket and put a 3/8" open end wrench on the male side and used a pvc pipe for more leverage.

Bad news...when I took the plug out not a drop of fluid came out. Started going at it with a screwdriver and found this Even after proving around in there getting a pile of stuff out coolant still won't flow out. So I'm sure its safe to assume this is how the whole block is... what are my options? Do I have to do a complete tear down?

I dont know if this would work, but I would go get an adaptor from garden hose to 3/8 npt, then run the hose into that drain for a while with other hoses or plugs open. if you can get water flowing the opposite way, you can alternate flow back and forth to rinse the crud out. might be worth pulling the freeze plugs if you can access them easily to flush from there as well. you will need new ones if you do.

After more poking with a longer screw driver I was able to get coolant to drain from that plug. I thought about removing the freeze plugs but I would need to pull the intake and exhaust manifold off to reach them so I will wait on that for now. I thought about using an adapter like this https://www.amazon.com/FASPARTS-Female- ... B013XUKUBW to force water into that coolant drain but wondered if it would reach everywhere I need it to. Should I try running the motor with a garden hose going into the inlet hose and direct the outlet hose away from the car while leaving the drain plug out?

...obviously I am going to need to turn the radiator upside down and flush it heavily

Maybe run some radiator flush in there too (follow instructions and don't buy the cheapest stuff)? I think flushing w/garden hose is worth a try, maybe from rad side and drain plug side, and with engine running at different speeds. Hard to say if it will work, but worth a shot.

Lou

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Home of Slant6-powered fun machines since 1988

If you are going to pull the radiator anyway, you might pull the water pump as well.
That will give you at least a little access to the front of the cooling jacket.
Then your reverse flush through the block drain will be able to push crud right out the front.

How about plumbing a small pressure washer straight into that drain port?
The common quick connectors are 3/8" thread.
Even though you won't be able to direct the flow, the extra energy in the stream should help dislodge as much as possible without major disassembly.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

I like your extreme measures way of thinking, Mr. Inthehead!

Lou

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Home of Slant6-powered fun machines since 1988