2001 300x Over Heat Fault STB Side/Guardian Mode Enabled

[Nikon Man]

What's up with this ??? Had good water presure, 10 PSI @ idle (has new pump) and around 12 PSI + at above 3500, neutral trim. Idles at 130 and @ 3500-4000 up's to 150 and holds while running at that RPM, more RPM/speed more heat, reduce RPM/speed and temp comes down. Hot water tested the stats and there per the manual start to open at 120/125 and fully open @ 130+..........hoses are all new from the stat housings too, S/Master water intakes are free and clear, what the heck did I miss..... .........0T235158

[RoadrashPaul]

Poppet valve maybe????? I don't know just thinking outloud......

[spider1]

How about a blown gasket???

[Nikon Man]

Poppet..........maybe, haven't checked that yet. As for head gasket "O Rings", nope got great compression and leak down numbers.

[blair]

Man, I hate that for you Gary. It always seems to be something......


I'm sure with Don's guidance and your perseverence, you will get it right.....

[Nikon Man]

Good thing I'm not heading to Vegas anytime soon.........with my luck I'd be broke in a minute.................LOL

[EuropeanAM]

Gary:

10 psi at idle is CRAZY high for that engine. Should be minimum 1-3 psi (and should not exceed the poppet spring pressure under any idle conditions- which is approximately 7 psi).

Your WOT pressure should be 18+.

Did you replace the powerhead gasket when you had the p/head off (I don't recall)? Leaks between the exhaust and water passages can affect water pressure, and cause overheating.

Might also want to take a close look at the poppet valve- ensure it's in good condition, and that the plastic poppet slides FREELY in and out of the grommet/seat.

Seat should be secure in the adapter plate (stays put).

Also, take a close look at the poppet SPRING for signs of exhaust carbon. Exhaust carbon on the poppet spring is a "dead giveaway" that you have a leak between exhaust and water passages at the powerhead (or adapter plate) gaskets.

[Nikon Man]

Don,

Everything was new, you may not remember but I had to do a complete reseal on the block to front half because of oil/fuel leaking at the bottom of the block. All the gaskets I got from you all matched the parts manual numbers so I know that they are the correct ones.

I pulled the Poppet out last night, and it's perfect, spring is clean, diaphram is undamaged (no holes or cracks) actually looks new and movement is unobstructed.

I've swapped the temp sensors in the heads to see if the fault follows the swap....I figured why not, easy test...

I'll report back after this weekend if anything changed..........

[EuropeanAM]

I did remember that, just couldn't recall if the p/h gasket was changed or not.

Out of curiousity.... are you reading water pressure on Smartcraft, or on an Analog Gauge?

WOT water pressure?

One thing I find is that sometimes, the water inlet passage gets WOOD in it. The wood can become trapped BELOW the water pump (larger metal plate that bridges across water pump and shift shaft housing area). Pieces of wood float around here... blocking portions of the flow area, and cutting down water pressure at higher RPM's.

This can prevent proper function of the poppet valve, forcing the engine to attempt cooling through the thermostat circuit (which is insufficient to cool the engine at RPM's above 2500-3000).

Water pressure and cooling function (in this case) would normally be fine BELOW 3000 RPM's, but temps would rapidly increase (and water pressure would be low) at higher RPM's.

[Nikon Man]

Don,

Just got back from the river and my Over Temp fault went with the sensor after I swapped them. I stopped at a Marina on the river that was open this morning and picked a new one up........problem gone.

My readings are on an analog gage, but the truth comes out on my DDT....LOL

[Largemouthlou]

Glad to see ya got her fixed!!

[Nikon Man]

Thanks Lou,

It had me going there for awhile since both sensors checked ok with an OHM meter at ambient temperature, but that electronics for ya, always there to throw ya for a loop...............

[EuropeanAM]

Gary:

Glad to hear you got that fixed.

One "trick" you can use: On the DDT (or the CDS), view all temp sensor temps on a COLD engine. Any sensor reporting a temp more than 5 degrees outside of the others should be considered "suspect".

Port Temp, Stb Temp, and IAT (Intake Air Temp).

The "culprit" will often be WELL out of range with the others.

[Nikon Man]

Thanks Don, good info to know.