2002 SANTE PCM GT40 5.8 Ford cooling system diagram? Overheating issue.

[2002sansac]

Does anybody have a block diagram of the cooling system for the PCM GT40 5.8 engine? The PCM parts list of the cooling system compoments would also show me the way. The cooling system for the boat includes the thru-hull suction fitting on the bottom of the hull, strainer, raw water pump, thermostat housing on engine, hose routings to port and starboard exhaust manifolds, circulation water pump on engine, cooling hoses to Walters V-drive unit, cooling hoses to heat exchanger for transmission.

Chasing an engine overheating issues and I need to understand the system before just throwing psrts at it. Impellar was replaced and issue returned about 3 hours later. Condemplating replacement of thermostat however, I would like to understand why the engine is overheating.

[Tom_H]

How was the impeller that was removed? If it was missing any pieces, you need to find and remove them, as they can plug passages and allow more overheating. Sometimes they end up upstream or down, but check the thermostat housing, hoses to exhaust manifolds, oil cooler, etc. Beyond that, often times, overheating can be caused by an air leak on the inlet side of the raw water pump, most commonly from the strainer bowl not being sealed all the way. But also check that all hose clamps are tight.

[JayG80]

While you are waiting on the diagram, try a couple of primary steps. The first 2 steps help eliminate air infiltration into the system that leads to overheating.

Remove, clean and inspect strainer for cracks. Put Vaseline on the rubber gasket and re install.
Use a nut driver to tighten all the hose clamps in the cooling system.

[2002sansac]

Excellent suggestions from Tom and Jay, thanks!

The impellers that have been removed over the past 10 years or so, have been in fairly good condition. None of the impellers have been torn or have had missing rubber material, however, there is a possibility. I did locate a cooling hose that had a cracked all the way through. It was the the 8" long X 1" ID cooling hose that goes from the thermostat manifold to the exhaust manifold, just before the exhaust riser (port side of boat).

I will check the strainer bowl o-ring and ensure proper installation and seating. I do realize that any air leakage downstream of the raw water pump will effect the volume of cooling water provided to the engine.

So, out to the lake for a test of the cooling system. I will post the results. Its **** hot in Sacramento and I dont want to wrench on it in 100 degree weather, if I dont have to. The next step is to replace the thermostat if the boat still runs hot.

[2002sansac]

So, I tightened up all the hose clamps on the cooling system, most were snug and I applied a bit more torque on the hose clamps. I also removed the strainer bowl and o-ring and reinstalled using a thin cost of vasoline on the o-ring.

I ran the boat on the lake yesterday and here what happened. The tempeture came up to 155 on the gauge and I ran the boat under all rpm levels and loads. After about an hour or so, the tempeture was steady at 155. As I recall from previous trips, the tempeture ran at a solid 160. Hmm? I was thinking the thermostat was not operating correctly. After the hour or so the tempeture started to rise, 180, 190, 200, 220 and 240, I turned off the engine and let it sit for 20 minutes or so. Same high tempeture after restart, I called it a day and got towed to the boat ramp.
I toredown the thermostat manifold and removed the thermostat and tested it on the stove. It starts to open at 160 and fully open at about 180. The thermostat is operating correctly. Crap! Now what is the problem? Cooling water is either: 1.Cold water is not flowing to the raw waterpump or, 2. Hot cooling water is not exiting the engine somehow.

I plan on back flushing the cooling hose from the raw water pump back through to the strainer and to the through hull fitting on thr bottom of the boat. I also plan on flushing the cooling circuits of the exhaust manifolds, v-drive gearbox and the transmisson cooler. I hope to capture any material obstructing the flow of cooling water from these locations.

Help, I am running out of ideas.....

[JayG80]

We ran through this recently with a neighbor on his 02 Ski Nautique.

He tightened all the clamps and checked the strainer bowl for cracks.
He made sure the Raw Water Impeller was in good shape, some have been known for the rubber to spin around the hub.
Used an IR temp gauge and both manifold risers were close in temp.
Inspected the pump to make sure it was not mounted upside down. Temp immediately pegs high if it is.
We suspected the face of the impeller housing wasn’t making a good seal, cleaned and replaced oring
Removed pump again and added custom gasket material.
Pulled hoses from both ends of the transmission cooler and looked for blockage inside the cooler and hoses.
Replaced thermostat and cleaned gasket surfaces well
Pulled the hose off the exit side of strainer basket and put it in a bucket of water.
Pulled the hose off the exit side of the raw water pump. Ran the boat and water draw down from bucket was minimal.
Looked at transmission cooler and he over tightened the hose clamp with socket and crushed one side of the transmission cooler.
Replaced the damaged cooler and did another bucket test, still weak.
Finally were down to a weak raw water pump. We felt the pump must be leaking air in the housing and causing cavitation and weak pumping.
He had already tinkered with cleaning the mating surfaces of the pump housing testing with new ring, and then later added a hand cut gasket.
He was going to buy a full G21 rebuild kit but the summer was winding down. He went ahead and bought a new complete pump.
New pump solved it. I also believe somewhere in there, one hose end between cooler and pump looked suspicious and he replaced it without any benefit.

[Rednucleus]

Maybe a failing motor circulating pump (not the raw water pump)
Have you ruled out a gauge gremlin saying it's hotter than it really is; do you get an alarm at 240??

[JayG80]

https://youtu.be/c5TEBV8NrjQ Good cooling intro system video

https://youtu.be/AE37Gt70DF8. Bucket feed shows rate the impeller draws in water

https://youtu.be/ibgI2Md1Pe0. Changing Impeller by Discount Inboard Marine

[2002sansac]

Informative info and video from the members.
So, here where I'm at:
Tested the raw water pump using the 5 gallon bucket and hose method, plumbed water from the intake side of the water strainer. Very good flow on the output side of the raw water pump. Hose connected to the seacock might be an issue, however, all clamps tightened up.
Inspected the inlet to the transmission cooler, no debris present (did this prior to raw water pump test).
The t-stat was tested on the stove, along with the new replacement. Both opened as they should at 160 F.
Flushed the exhaust manifolds with the large brass plugs removed. Flushed from the two 1" hoses attached at the t-stat manifold. Both flowed water just fine.
Attempted to electrically test the temperature sender located on the circulation water pump. I didn't have the resistance values for various temperatures so, I gave up on this.
Belts snug on the pulleys, so this is not as issue.
All clamps tightened up on trans cooler, water strainer, v-drive gearbox, exhaust manifolds, thermostat manifold, circulation pump and elbow, all good.
All associated hoses reinstalled and tightened, and a new t-stat and gasket installed.

Out to the lake for a test run.
The temperature on the cockpit gauge read 180 after only 1-2 minutes of idle. Ran the boat for about 35 minutes, temp solid at 180 F....huh? should be 160 F.
Inspected all hoses for leakage-no leakage.
Used IR handheld unit to check temperatures; Exhaust risers at 123 F, circulation pump surface at 143 F, engine block at 143 F (difficult to find a representative surface).
Strainer is full of water with no bubbles as engine runs.
No leakage of hoses, minor water in bilge.
Engine temp should be 160 F, what's going on?

I'm thinking the water temp sensor is the culprit. I decided to remove it, however the lower portion of the t-stat housing (bolted to block) must be removed, to remove the sensor. When unscrewing, the sensor electrical stud will hit the t-stat manifold above it.

To be done:
Test cockpit gauge by grounding the signal wire to the block. Should indicate full scale movement and peg the needle.
Replace the water temperature sensor installed on the circulation pump. T-stat housing must be removed to gain access.
Parts on order.

If anyone has a suggestion on the issue, I'm all ears!

[2002sansac]

So I took the boat out again to check temperature. I taped a type-K thermocouple wire on the surface of the circulation pump just adjacent to the OEM temp sensor screwed into the circ pump. This way I could measure temp through the circ pump-used a digital readout DMM for temp.
Ran the boat under all conditions and the temp is steady at 125 F, I don't get it? It should read 160 F.

Plan to replace the temp sender in the circ pump when I get the parts.

[Aaren22]

What ended up being the problem? Im having the same issue.

[2002sansac]

So here's where I'm at:
At the end of last summer I put the boat in dry storage and figued I'd replace the thermostat and tempeture sensor in the summer. I typically don't like to just throw parts at an issue, however, I had nowhre else to go.

This summer:
Replaced the thermostat and OEM gasket (when I reinstalled the t-stat last summer, I did not have the OEM gasket, and I made one, upon removal the gasket looked like it had not sealed sufficiently, ie the OEM gasket is thicker than the one I had made). Replaced tempeture sensor located in the circulation pump. My son, a fairly good wrench, and went for a test ride, the issue seems to be solved, running at a solid 160 degres. I'm thinking thst the tempeture sensor had an offset, as the original sensor did read in a linear fashion, however, I did not test the replacement sensor and compare it to the new sensor, failure on my part.

I still have to take a ride to verify that the temp runs at a solid 160 degrees.

If I had to do it again, I would start at the water intake thru hull fitting and go and go step by step all the way to the raw water pump. Verify that there are not any cracked hoses, or loose hose clamps. The raw water pump pull a vacuum (sucks) water starting at the thru hull fitting, up thru the water strainer assembly and ultimately the raw water pump. I dont recall but, the water circuit may go thru the v-drive gearbox cooling jacket prior to ending up at the raw water pump. If any of these hoses or clamps create a leak, its like trying the pull soda out of a glass with a cracked strsw, it dont work so well. To determine the compoments prior to the raw water pump, just visually trace the hoses that terminate at the raw water pump inlet, easy.

Also check all the hoses and clamps on the remainder of the engne, circulation pump, echaust manifolds, heater hoses, etc.

The impellar is a wear items and should be replaced every season

Also check/test the thermostat and the tempeture sensor on the circulation pump.

And there just might be electrical issues with the tempeture gauge, however, I have no idea how to test this imstrument.

My two cents worth.

Best of luck with the issue.

[2002sansac]

btw, I was able to replace the tempeture sensor fof the dash gauge without removing the manifold above it. Its tight but can be done.