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454 overheats at idle

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wej55

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"I have a 1995 7.4 throttle bo

"I have a 1995 7.4 throttle body injected moter that runs up to 200* at idle. When you run up the throttle it cools right down. I have cleaned out the heat exchanger and the u cooler, replaced the water pump impeller and also the t-stat.Both engines appear to be discharging the same amt of water. The starboard eng water discharge is extremely hot.What next ?"
 
Confirm that your gage is accu

Confirm that your gage is accurate by checking it with a digital pyrometer.
 
The gauge is correct. The wate

The gauge is correct. The water discharge is so hot you can't touch it.
 
"Take your imaginary pyrometer

"Take your imaginary pyrometer and check the engine at different locations, compare those readings with those taken at the same locations on the other engine. You may find a hotspot on the engine somewhere due to a blockage or delaminated hose.

How was the pump housing? Physics dictates that the same amount of water transfers the same amount of BTUs regardless to which engine it is going through. The water flow may look the same but if the temp cools when the RPMs, and therefore waterflow, increase, I would have to suspect a waterflow issue.

The only other possibility could be that one engine is generating more friction (heat) at idle than the other. That's a whole new thread."
 
The pump appears to be fine. I

The pump appears to be fine. I will check the temp as you suggest at different locations. I was also thinking about bypassing the u cooler for trouble-shooting. Any thoughts on that? Thanks.
 
"If I were looking for a water

"If I were looking for a water flow problem, I would certainly try that. You may save some time by squeezing the inlet and discharge hose withy the engine running. If the inlet is harder than the outlet, you should be real suspicious of the cooler."
 
"Crusader cooling sometimes se

"Crusader cooling sometimes seems a mystery. I think the reason is that there can be a number of problems that can contribute to overheating or steaming out the exhaust. Humidity definitely has an influence on the steaming. I find a larger contributor to be the amount of raw water being pumped into the system. It is almost impossible to judge the amount of water exiting the exhaust pipe. It is being blown around by the exhaust. You need to make a measurement to see if the pump output is as it should be. Crusader instructed me to take the hose loose going to the manifold and put it in a bucket and measure the amount over time. When I go back to my boat this weekend I will look up the specification they gave me and put it here. I believe it was 12 Gallons per minute. Half that amount won't keep the engine cool and it will steam out the exhaust. If the flow is low, it could be due to a number of problems that have been pointed out already.

Chuck Hanson"
 
"Check for vacuum leaks and al

"Check for vacuum leaks and also timing. I had a base plat gasket get injested under the front of the carburator and it was sucking a huge amount of air, running too lean.

Dont know much about the TBFI model but there could be a fuel to air mixture issue. Too lean and it will run hot."
 
I am on my boat this weekend.

I am on my boat this weekend. Crusader told me the flow rate at the thermostat box should be 12 gallons per minute at 1000 RPM. That is for a 454 CID.

Have fun.

Chuck Hanson
 
Thanks guys. I ended up replac

Thanks guys. I ended up replacing the u cooler and she runs at 160 now. Hopefully that's the end of that. Now the bleaping gen set won't charge the battery.
 
The engine is still running fi

The engine is still running fine. I have heard that these u coolers are suseptable to clogging due to their design.I guess the pencil zincs clog the bottom of the u cooler when they breakdown. I am having the cooler cleaned out and will try again. Thanks again.
 
Coolers clean out easily using

Coolers clean out easily using 50/50 muratic acid and water. pour it through until it quits foaming. If real bad a radiator shop can unsolder the end and clean it out. The tubes inside are braised so unsoldering the end will not disturb them.
 
After almost 3 weeks the probl

After almost 3 weeks the problem came back again. Sitting at idle the temp runs up to 200. Then if the throttle is increased the temp comes back down. Why would it run normally for almost 3 weeks and the all of a sudden overheat again?
 
"You gotta be pumping some kin

"You gotta be pumping some kind of crud through it that plugs the unit. Do you have a good, operating strainer in the system?

Jeff"
 
Actualy no. There are no strai

Actualy no. There are no strainers on either engine. What puzzels me is it is only one engine.Could there be air somehow getting into the system?
 
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