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Old 08-02-2018, 07:44 AM   #1
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Chrysler 318 Thermostat

Hello All. Datenight our North Pacific 39 has been sold and we await the delivery of our next Datenight a North Pacific 45 in late November.

Diane, the High Commander, decreed we will not be without a boat this summer. Enter Cheap Date a 1976 Trojan 28 Sedan Bridge.

It fits our need perfectly and runs well except for the exceptions. The port engine runs hot and seems to use coolant. I can find no leaks and an inspection of the raw water side of the heat exchanger shows no antifreeze. Running the engine with the coolant cap off shows no bubbles eliminating (I hope) a bad head gasket.

Port engine sends coolant to the hot level of the overflow tank but does not suck it back when the motor cools. Yesterday I changed the cap to a different one that came with the boat. No coolant left in the on engine tank, overflow full. I did notice that the cap on the overflow was loose. Must have forgot to tighten it.

Today I will drain the overflow, make sure the cap is tight and buy a new "radiator" cap. My next thought is the thermostat. The coolant tank on engine is square with two bolts sticking out of the top. Everything I see on line is round for the 318. Can't find a thermostat housing anywhere and suspect it may be under the tank.

The photos I took with my phone won't transfer to my laptop so I will try to post them later.

This would not be a big deal if we were home but we are five days into a two week cruise. I have been in contact with my mechanic but have not found the solution yet. I am hoping the TF brain trust can come to the rescue.

Thanks,

Rob
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Old 08-02-2018, 09:51 AM   #2
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Here are the pictures of:

1. Coolant Tank 2. Hose from bottom of tank to temp. sender.

Coolant goes from temp sensor to engine circ. pump, block, heat exchanger and back. I seem to have plenty of raw water coming out the exhaust.

Rob
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Old 08-02-2018, 10:34 AM   #3
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How hot is it running? How hard are you running it? Verified temps via IR gun?

Tstat is "probably" under that tank secured by the two nuts. I think the normal tstat location on the 318 is the center front of the intake manifold. So it should be under that tank, but there are some weird plumbing systems out there!!

Have you cleaned the heat exchanger? Gear cooler? Might have a sea water engine oil cooler too.

Make sure you get the "recovery type" pressure cap. Has an extra gasket that lets it suck back from the bottle.

Go around and snug EVERY hose clamp on hoses that carry coolant.
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Old 08-02-2018, 11:49 AM   #4
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Both fresh and salt water systems could need a flush. Rust can build on the water jackets and head passages acting like a insulating blanket, limiting the transfer of heat. Also rust flakes can break off and block passages. When I was in business, I fixed a bunch of engine heat problems on the fresh water side, just by doing a proper flush. The fresh water components need routine corrosion cleaning just like a car.
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Old 08-02-2018, 12:00 PM   #5
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When I had my Blue Water 40' with twin Chrysler 318 - 240hp, the exhaust manifolds were fresh water cooled. I had a leak in the block off plate / gasket between the manifold and riser that would eat about a quart of antifreeze per hour. Only leaked under pressure but would allow enough air into fresh water side so never pulled back from overflow tank. I made new block off plates and gaskets to go under the 4 risers ... no more coolant issues.
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Old 08-02-2018, 12:04 PM   #6
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Thanks Ski,

The gauge went to 200* before I shut it down. Yesterday it stayed just below 180* but we only ran for about an hour. When I checked after cool down the overflow was full and expansion tank empty. Will verify tomorrow with an ir gun.

I took the end off the heat exchanger but did not check the other coolers. That along with checking every hose will be my project for the afternoon. Did buy a new recovery type cap that will go on today. The "original" one said 13 lbs so that is what I bought.

Thanks,

Rob
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Old 08-02-2018, 09:29 PM   #7
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OK,

I pulled the heat exchanger this afternoon. the tubes were relativly clean but could benifit from rodding out. I could easily see through 80% of them. Not possible due to the design to see through all of them.

I did find a piece of impeller 1/2" wide by about 1 1/4" long. Looks to me like it could have blocked about 20-25% of the flow. Don't know if it is from the present impeller or a past unit.

The only other cooler was for the gear. It had what looked like barnicle/salt lumps in the bottom. I could easily see through 90% of the tubes.

Replaced expansion "radiator" cap with new 13 lb.

Our next stop tomorrow is Battle Ship Cove in Fall River, MA. I will do my best to find an impeller and replace it. Will also look for a thin dowel to rod out the coolers.

After the clean out I ran the engine at a fast idle for thirty min. The temps by my IR thermometer were;

Top of expansion tank 147*
Bottom of ex. tank 142*
Temp sending sensor 138.5*
Exhaust manifold water inlet 116.5*
Center ex. manifild 157.5*
Riser 104*

I imagine the temps will be higher under load. Will report tomorrow.

Any comments welcome.

Rob
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