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Old 07-10-2011, 04:56 PM   #1
351cmach
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Default Flathead overheats 1 side

My 49 merc flathead overheats on 1 side. The left side runs 190 and the right side will get to 230 before I shut it down. These temps are with an ir termometer at the t-stat housings. These temps are taking just after a drive but they will be about the same at idle. The engine is stock , with duals. There are no thermostats, no resrictions in the exhaust (flapper valve moves but does not come into play with the duals) timing is correct, engine is not running lean, no combustion gas entering the cooling system, has new rebuilt high flow waterpumps, flushed the block with water with the heads and pumps off. In the block is a bit scaley. I am in the process of doing a vinergar flush. The radiator seems to flow ok a temp drop of about 50 degress top to bottom, but the bottom left is a little cooler than the rest of the radiator.
What do you think? Do I need to install the t-stats as a restictor? But it seems a bit odd its only one side?
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Old 07-10-2011, 05:43 PM   #2
Chris Nelson
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Default Re: Flathead overheats 1 side

Have you checked the water passages in the block for sediment/foundry sand? Henry Ford was not too critical about getting all the foundry sand out of the blocks and over time it migrates to the back of the block. A long screwdriver could be used to check how deep each side is through the water jscket holes and compare from side to side. When my blocks were built, they were rolled back and forth on a sheet of plywood and prodded through the water jascket ports with a sharp pointed screwdriver. Prod and roll, prod and roll and the result was over a quart of old foundry sand fell out of each engine. Both of mine run 185 degree thermostats and hold that temp. despite long idling or highway driving. I did drill a couple of holes in the thermostate butterfly to allow any air to leave as it was being filled with 50/50 mix of water and antifreeze. I have checked the temps with a electonic thermomoter and both side run the same.
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Old 07-10-2011, 06:19 PM   #3
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Default Re: Flathead overheats 1 side

The only common area to the two sides is the radiator. If you have a compression leak into the hot side or a sticky thermostat on that side, it will run hotter. I'd check the easiest thing first and go from there. Since you have no thermostat, I'd check the plugs for signs of water leak and do a compression check on that side first.

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Old 07-10-2011, 07:06 PM   #4
351cmach
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Default Re: Flathead overheats 1 side

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Originally Posted by rotorwrench View Post
The only common area to the two sides is the radiator. If you have a compression leak into the hot side or a sticky thermostat on that side, it will run hotter. I'd check the easiest thing first and go from there. Since you have no thermostat, I'd check the plugs for signs of water leak and do a compression check on that side first.

Kerby
Allready checked for combustion leak on that side. The plugs do not show any signs of anything being off, Compressions all good, if I had low compression I would not be creating as much heat. And no water or condensation from the exhaust pipes.
I believe I have covered everything I could think of.
Maybe I will have some luck when I'm done with the vinegar flush
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Old 07-10-2011, 09:03 PM   #5
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Default Re: Flathead overheats 1 side

Try disconnecting one spark plug wire at at time on the affected side and let it idle. Use your Infrared Thermometer to isolate the cylinder or cylinders that are overheating. This would be a start and a place to look closely at should you have to remove the head.
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Old 07-10-2011, 09:34 PM   #6
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Default Re: Flathead overheats 1 side

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How about the radiator hoses on that side? They can look good on the outside but be collapsed inside as they are usually double wall and the inside walls can collapse. Happened to my dad on his freshly rebuilt '40. It kept getting hot until one day he got mad and kept driving home (yeah, it cracked the block!) He had checked everything, he thought, but after the damage was done he cut the upper hose in two on the hot bank. The hose was collapsed inside. When I asked him how old it was, he said "It's the original as far as I know! I never changed it." He grew up during the depression so wasn't about to buy anything he didn't think it needed.
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Old 07-11-2011, 07:58 AM   #7
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Default Re: Flathead overheats 1 side

"Allready checked for combustion leak on that side"

How do you check a side for a combustion leak? Only way I know is to do the check of your radiator water for combustion gases. If you detect the gases then it follows that may be the cause of your high temperature on that one side. I'm just asking because I would want to learn of any new test that might be out there.

Also, may I suggest that you put your locale on your thread ID? It is nice to know how extreme hot running engines are given where they are located. In other words, driving your flathead here in S. Texas this summer and it getting hot is kinda expected. However, if you are driving it on the Oregon coast and it is getting hot, then you really have a problem.
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Old 07-11-2011, 08:14 AM   #8
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Default Re: Flathead overheats 1 side

I had an overheating problem with the 46 truck we used to go to Hershey and other flea markets in, , it was only on 1 side, after duals were installed, the problem turned out to be the muffler ---who would have thought a muffler for a mustang with a 302 wasn't flowing enough to handle 4 cyl of a flathead, installed another "stock type" muffler and no more problem.
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Old 07-11-2011, 08:50 AM   #9
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Default Re: Flathead overheats 1 side

Any chance you have a mis matched head gasket on that side and are blocking some of the water outlet or passages? Just a thought.
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Old 07-11-2011, 12:43 PM   #10
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Default Re: Flathead overheats 1 side

how's the waterpump on that side??...maybe belt slipping and not allowing it to turn as fast as other one??....maybe clogged passages in head??....you could check flow from both sides, i guess.....good luck...Mike
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Old 07-11-2011, 01:19 PM   #11
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Default Re: Flathead overheats 1 side

Some very good suggestions here .A cylinder leak generly dumps water out the overflow . Something to try is to cross over the bottom radiator hoses ,get some Constantine hoses ,see if the problem swaps over .
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Old 07-11-2011, 02:54 PM   #12
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Default Re: Flathead overheats 1 side

Quote:
Originally Posted by 36tbird View Post
"Allready checked for combustion leak on that side"

How do you check a side for a combustion leak? Only way I know is to do the check of your radiator water for combustion gases. If you detect the gases then it follows that may be the cause of your high temperature on that one side. I'm just asking because I would want to learn of any new test that might be out there.

Also, may I suggest that you put your locale on your thread ID? It is nice to know how extreme hot running engines are given where they are located. In other words, driving your flathead here in S. Texas this summer and it getting hot is kinda expected. However, if you are driving it on the Oregon coast and it is getting hot, then you really have a problem.
The way I do it is to take the belt off so the water pumps cant turn. Then remove the hose from the water neck on the head and remove the thermostat. Fill the head with water all the way up till you can see the water in the neck then crank it up. If combustion is getting in the water jacket the water will rise and you will see bubbles.
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Old 07-11-2011, 03:23 PM   #13
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Default Re: Flathead overheats 1 side

Are you using an off set generator? On the side with the offset, there was little belt overlap with the water pump pulley, I could easily slip it even when the other side's water pump pulley was tight. I had a 20 degree difference in temperature. I made an idler pulley setup and the temps became the same.
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Old 07-11-2011, 05:27 PM   #14
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Default Re: Flathead overheats 1 side

Thank's, Ken.
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Old 07-12-2011, 10:59 AM   #15
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Default Re: Flathead overheats 1 side

Quote:
Originally Posted by FlatheadTed View Post
Some very good suggestions here .A cylinder leak generly dumps water out the overflow . Something to try is to cross over the bottom radiator hoses ,get some Constantine hoses ,see if the problem swaps over .
Yes, half a radiator can be blocked - had this on my '36.

Quote:
Originally Posted by Ken/Alabama View Post
The way I do it is to take the belt off so the water pumps cant turn. Then remove the hose from the water neck on the head and remove the thermostat. Fill the head with water all the way up till you can see the water in the neck then crank it up. If combustion is getting in the water jacket the water will rise and you will see bubbles.
Be careful, you can also get localized boiling in tiny areas first - just like the bottom of a pan of water on a stove - don't be confused - best way is to use a chemical tester that changes the testing solution color in the presence of combustion gases. You can do that on the radiator neck - it really doesn't matter which bank is leaking, I think you already know!
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Old 07-12-2011, 11:13 AM   #16
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Default Re: Flathead overheats 1 side

Sometimes we get lucky here and this works: Pour a box of granulated Cascade in the radiator.The water will likely turn rusty.Drive it awhile and drain it.Many times this will work and nothing is cheaper.James
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Old 07-18-2011, 06:41 AM   #17
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Default Re: Flathead overheats 1 side

I had the same problem on my 46 Coupe except it was the driverís side running hotter. After having the radiator thoroughly cleaned, flushed and bent fits straightened (knock on wood), she has been running cool with even temperatures on both sides. I am convinced that 90% of overheating problems can be attributed to dirty radiators. Good luck. Steve
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