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1988 5.7 Crusader Full fresh water cooling runs warm

T

timmy66commander

Member
Hello,

Looking for some insight on an engine that runs warm.

Left engine runs warmer about 20 degrees from right engine. Manifolds are full fresh water, elbows/risers(2014) fairly new. Raw water pump rebuilt last winter. No coolant loss over summer of running (head gasket/Heat exchanger ok?). Thermostat (new/160 deg). No blockages on raw water side heat exchanger (took side plates off). I am able to swap the output of each raw water pump to the other engine by moving hoses on raw water strainers and the issue stayed the same (not a raw water issue?)

I used an IR temp gun to look at temps of both engines while fully warmed up and compared. The thing that jumps out at me is the following......

The coolant temp at thermostat output is 20 degrees warmer (167deg) than on good engine (145deg). The coolant temp going to input side of engine water pump coming from Heat Exchanger output is about the same as good engine (122 deg) but after engine coolant runs thru block/intake manifold/cylinder heads it comes out 20 degrees warmer on suspect engine. The left/right side about same temp (one side is NOT hotter than other)

Am I looking at a engine cooling water pump/ blockage in block/bad intake manifold?????

Ideas??

Timmy
 
Good stab at decent diagnostic info....not sure moving the hoses from the strainers will do what you want....but you can see what there and what's going on....(strainers should be on the INLET <suction> side of the pumps.... assuming that's correct, it would appear the issue is on the coolant side and the engine circulating pump is very possible....could also be reduced flow due to the supply hose (from the HX) collapsing.

Cause could also be something on the mechanical side cause that engine to run harder/get hotter (lean condition maybe)...

After rereading the post, the 'tstat reading of 145 on the good engine sounds low....the standard tstat is 160 degrees so the 'good ' engine appears to be running cool.....
 
The good engine at 145 deg (thermostat housing), regardless of how hard run (>3000 rpm) does not move above 160 deg on engine gauge. The left (hot) engine temp will climb above 180 degrees if run above 3000 rpm in very short time.

thru hull>strainer>raw water pump>engine..... swapped strainer output hoses. This ruled out thru hull, thru hull hose, raw water pump (I hope)

HX to engine water pump hose is hardwalled. Temp at coolant input to water pump (from HX) was same on both motors. but not sure how to check for reduced flow

each engine has separate fuel tank, fuel burn over 70 Nmiles is within 5 gallons


Best guess as to next step?
 
Does not exactly match your scenario, but a common but overlooked overheating cause is a clogged oil cooler. Worth checking.
FL Panhandle
 
swapping the strainer outputs only changes the supply to the raw water pumps....so the raw water pump is still a potential....if it has issues, it could also cause the situation like Mullet suggests....

when was the last time the raw water pump was serviced???
 
Maybe swap t-stats ? Might put both in a pot of water and see if they open the same time as the heat increases. Sounds kind of Mr Wizard (for those over 60 - LOL.
 
I had the same issue on my 350's that were a full fresh water cooled. I did many of the things you have already checked but found the problem only went away after I swapped out the risers with a spare set I had. It seemed they were plugged up with rust and restricting the raw water flow thru heat exchanger.
 
Tim, the term FWC or Fresh Water Cooled is still being used by some, inluding Heat Exchanger manufacturers.
However, this is a misnomer and is a carry-over from the old days.
Today's systems are actually a CCS or Closed Cooling System. (there's nothing fresh about Ethylene Glycol and distilled H2O :D )

timmy66commander said:
Hello,

Looking for some insight on an engine that runs warm.

Left engine runs warmer about 20 degrees from right engine.
Are you relying on the temperature gauges at the helm, or have you checked with an IR gun?
If you rely on the helm instrument, swap leads and/or temp senders as to verify!


Manifolds are full fresh water,
IOW, the manifolds are also part of the Closed Loop..... correct?


Raw water pump rebuilt last winter. No coolant loss over summer of running (head gasket/Heat exchanger ok?). Thermostat (new/160 deg). No blockages on raw water side heat exchanger (took side plates off).
This covers the ID of the tube bundle, but you also have the exterior of the tube bundle to consider! (I.E., the Ethylene Glycol side!)
If the E/G side has a build-up of rust scale surrounding it, it will hinder the heat exchanger's ability to remove engine heat!

I am able to swap the output of each raw water pump to the other engine by moving hoses on raw water strainers and the issue stayed the same (not a raw water issue?)
I'm not following you on this one!

I used an IR temp gun to look at temps of both engines while fully warmed up and compared.
OK..... then scratch my earlier comment!

The thing that jumps out at me is the following......

The coolant temp at thermostat output is 20 degrees warmer (167deg) than on good engine (145deg).
What is meant by "good engine"?

The coolant temp going to input side of engine water pump (aka Engine Circulating pump) coming from Heat Exchanger output is about the same as good engine (122 deg)

but after engine coolant runs thru block/intake manifold/cylinder heads it comes out 20 degrees warmer on suspect engine. The left/right side about same temp (one side is NOT hotter than other)
Have you swapped Port with Stbd and visa-versa thermostats as to further test?

Am I looking at a engine cooling water pump/ blockage in block/bad intake manifold?????
Ideas??
Tim, all are potentials!
With a Closed Cooling System, the automotive version circulating pump can be used. Likewise with the actual thermostat.

Question:
Is your Stbd engine a RH Reverse Rotation Engine????
If so, are you using a Circ Pump that is Bi-Directional????

A long shot...... engine build, ignition advance, etc, may have an affect on operating temperatures while under heavy loads.


Timmy
Click to expand...




mac9427 said:
Do the engine in question supply hot water to cabin, could have a slight clog.
Click to expand...
As in Cabin Heater or Water Heater?
If so, these are coolant supplied on a by-pass basis, meaning that the coolant leaves up-stream of the T-stat and returns to the suction side of the Circ Pump.
If anything, a cabin heater/water heater will further remove heat from the coolant.

That said...... and if all else is in good working order....... the engine's thermostat has the last word re; engine operatiing temperature!!!!
 
Last edited:
Is there a oil cooler? If so it is a common place for restriction in the raw water flow and a regular service item fill it with bleach water 1/2 1/2 and leave overnight and then back flush it good with the garden hose. Replace it if it is past its service life.
 
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