98 volvo 5.7 GLI Overheat conditon

S

stang32

Member
Joined
Jul 17, 2004
RO Number
14425
Messages
56
hey guys, a friend of mine is having a hell of a time with this overheat problem,
the engine temp climbs above 170 rb2@gr5t idle but not much higher, when you take it out & run it, the temp is steady rb2@gr5t 185ish. when you idle down, the temp spikes over 200, closed to 230.
the boat has new impeller, thermostat & manifolds/risers.
any thoughts
the impeller was changed for maintenance, not due to failure, no debri/damage found. the RWP runs off of the belt/pulley set up similar to the bravo set up but smaller,.
the RWP hose runs to the thermostat housing , which was also addressed & nothing found there.. the hoses all look in great condition, the boat has only been used on lake but it does have over 800 hrs on the motor.
any ideas on how to run down a blockage?

also, when first diagnosing the o/h the IR temp gun read 20 degrees hotter on the starboard riser than the port riser. after risers were replaced the same result only a bit cooler
 
One riser is normally hotter than the other. Can't help with the rest of your issue,
 
Agree with Gregory. The starboard riser on a normally running GM V-engine ALWAYS runs a little hotter than the port. As for the rest, the only part that really sounds abnormal is the spike when he throttles down. As a first step I think I'd use an IR temp gun to confirm that the spike is really happening, and not due to a faulty sender or gauge. 'Shoot' the t-stat housing at running temp and at throttle-down and confirm that the temp rises.

My .02
 
Plenty of water flowing through the exhaust? RWC? Not FWC, right?

I had to replace raw water pump to solve hi temp issues.
 
Running colder at sped pints to bad water flow at idle when speed is not forcing water in
 
I had the same issue, just a different motor. I spent nearly 2K in parts and chased it for over a year, only to find, when I pulled the engine for a different reason, that the water heater inlet and outlet had a plastic lining that had flaked off and was making a sort of check valve partly blocking the water flow.

Do you have an engine circulating pump? Also known as a water pump, not the one the impeller goes in............D............
 
Agree with Andrews above... If you've changed the raw water pump impeller and are still getting temp spikes when you throttle down, then I'd suspect the circulating water pump that is mounted right above the crank. Pull it off and check it thoroughly. My guess is you'll find something blocking one of the ports, or perhaps something inside the housing.

Adam
 
If it runs hotter at warmed up idle or low rpm than at cruise rpm , check for any scoring on the RW pump wear surfaces.

Also look for loose/leaky RW suction side hose connections any where after inlet to the RW pump. Suction air leaks generally have a limit so they affect heat more at low rpm but the ration of water to air increases dramatically at higher rpm. Sometimes higher rpm suction leaks will seal themselves as they pull the hose in tighter on a fitting until rpms go back down.

Does your friend reduce throttle gradually or "chop" the throttle RPM?
 
I don't recall the details, but I remember certain Volvo's having an issue with a fitting in the outdrive area that supplies water through the transom assembly and into the water pump. And, any I/O has a hose back there that can become a problem. Can collapse, break, kink...
 
the engine is RWC, no water heater, we have reduced speeds fast,chopped, & gradual with the same results.

today I put together all the parts listed on the overheat diagnostic pdf, only to get to the boat & find out all the hose sizes listed were wrong. the RWP on the boat runs off of a pulley, & not off of the crank as pictured in the PDF. so, anyway, I ran a bypass hose from the RWP intake over the side of the boat & directly into the lake with the same results.
i pulled the water outlet hose & ran the boat rb2@gr5t 1500 RPM to find that i am only pumping 3.25 gallons in 15 seconds, 1.75 gallons less than I've been told is sufficient.
I pulled the RWP to inspect, the impeller looks ok/new, the plate & cam look to have been re-used,
i pulled the thermostat & it does not look as new as I was lead to believe. i took it home & tossed it in a pot of boiling water, the therm started to open around 165 & didnt fully open until 175-180.
I would love to get a new RWP kit with the plate, change the thermostat & run the diagnostic test with the correct equipment once they are in.
my friend has layed out a lot of money on this boat & I need to be absolutely sure what I am suggesting is necessary.
thank you everyone for all your input, please keep it coming
 
It almost sounds as if you have a closed cooling T-stat instead of a raw water T-stat. Raw water T-stats are 140-145 degree whereas closed cooling T-stats are 160-165. The wrong T-stat is actually a common problem.
 
the RW t stat is a 160 , which is what it calls for. this is an EFI 5.7ltr gas engine.
 
since i did not have the correct hoses yesterday I will be going back armed with the correct ones tomorrow. i will get another hose that actually fits the pump & bypass the drive & p/s cooler. when i did it yesterday I saw a lot of air bubbles going into the pump, but that was probably because the hose was too big & I crushed it to achieve fitment.,
the boat has never been in salt water, always a lake, so if anything it is blocked by seaweed. I am thinking about putting the thermostat housing back in place without the thermostat to see if the issue is still there,.
 
I heard of problems with zebra mussels.

Long inlet sections with rubber hoses tend to collapse from the vacuum. You have to visually watch it while the temp spikes. Inlet hoses also should have the wire reinforced type...unless they are very short sections. You can use SS tubing on long straight sections

Also, I was wondering if you had different types of manifold/riser gaskets like merc does. Merc also has the spring loaded valves in the thermastat housing which regulates bypass flow past the engine.
 
today I put the pump & thermostat housing back on the boat & ran it without a t stat, the engine did not get hot at all, would not go over 120. tomorrow I will be installing a new t stat & see where that takes us.
my friend says the previous mechanic who "replaced" the t stat told him the old one had a chunk of impeller stuck in it. but the boat only has 8 hrs on it since this t stat was "replaced" & it looks like its been there for years. im just sayin......
 
You might want to consider putting a 140 instead of the 160 if on is available for it......D............
 
A 140 in a fuel injected motor will read havoc on the system. . But thanks for the input
 
He's in fresh water, so the 160 degree stat is actually better. They used to call for 140 in salt and 160 in fresh, but I don't think that's the case with newer engines. They used the 140 stats in salt to keep salt from precipitating out at the higher running temps of the 160 degree stats.
 
I missed this being an EFI engine, so yes you need to go with the 160 if that is what the fuel system is set up for..........D...........
 
You must log in or register to reply here.
Back
Top