Volvo Runs Cool

[Z71Man]

Hello all,
I enjoy reading this site and was hoping to solicit some help with a 1997 Volvo 5.7GL with an SX drive. It's in a Four Winns Horizon.

The engine runs cool most of the time and will only get up over 110-120 when idling or moving very slowly for at least 5-10 min. It's pretty consistent and the temp drops to the peg every time the boat is up on plane. I believe the gauge is correct because the engine feels fairly cool to the touch. I can comfortably put my hand on the exhaust and intake manifolds when it's running like this. Other than the temp there are no other apparent problems with its operation; no smoke, no starting troubles, etc.

I replaced the impeller and thermostat this winter and this did not solve the problem. It seems that it may run a little warmer but is still cool and not steady. Is there anything else that affects the operating temperature of the engine? Is this a problem that others with Volvos have?

Thanks in advance for any help!

 

[Don S]

Re: Volvo Runs Cool

Get one of those IR temp guns and verify the engine is actually running that cold. Could be a gauge/sender/wiring problem and the engine is actually running at the proper temp.

 

[johnbo]

Re: Volvo Runs Cool

Hi,

I hope that I can help. I had the exact same problem about two years ago. It would warm up, but as soon as the engine came up to speed, the guage would drop to dead cold or very close. Putting a hand on the exhaust riser confirmed that the engine was running very cold.

On mine (4.3L VP), the was a piece of rubber from the previous water pump impeller, that was jammed into a bypass tube that is cast into the thermostat housing. Apparently, it would pass enough water at idle to take the pressure off the thermostat, but when the engine speed came up, either the rubber would shift and jam the passage or it just couldn't relieve the pressure. The overpressure would (my theory) pop open the thermostat and cool off the engine. Took me a long time to figure out what could cause this, once I had a theory, I looked for the piece and found it. Completely solved the issue.

So, pull off the thermostat housing and find the bypass passage. It was about 1/4 - 3/8 of an inch in diameter. Its fuzzy to me right now, but you might have to pull out the thermostat. On mine, I used a piece of copper house wire (12 gauge) to poke into the passage. I could just barely see it, but I knew that it had to be there and it was. The rubber piece was a nice half moon sector of an impeller blade.

Go look for it, it will be there.

Later,

johnbo

 

[JustJason]

Re: Volvo Runs Cool

i'll second don....
we could all jump in and say this or that.
But what a mechanic would do is to check to make sure the engine is doing what the gauge says....
I make alot of money stripping wire back, putting in new crimps... cleaning up terminal posts... you get the picture.

 

[Z71Man]

Re: Volvo Runs Cool

Thanks for the replies. I'll set about to finding out whether the gauge is operating accurately next time I run it.

Jason, noticing your signature quote made me wonder if I could have put the thermostat in upside down. I'm wondering if it doesn't have the strength to stay shut if it's in the wrong way. I just assumed that the spring side should be down since that is how the old one was in there... Not sure if it would fit the other way.

If I take the thermostat housing off again, I'll definitely be more dilligent about checking for chunks of a previous impeller, as I know that one of the PO's destroyed one in it.

 

[Don S]

Re: Volvo Runs Cool

Upside down thermostat causes an overheat, not an overcool.

 

[aquamak]

Re: Volvo Runs Cool

Z71Man:

I have a '00 VP 5.7Gsi in my Four Winns 268 Vista and halfway through this past season, I started having the same problem. I went to a VP mechanic and said it could be 2 things: bad temp gauge or bad sender. I found info on the web on how to troubleshoot gauges and the gauge checked out fine. Then I checked the sensor and the ohm readings were a bit off so I replaced the sensor (about $19). The gauge came up a bit (to about 120 deg.). I found the true problem when I winterized this fall. The thermostat had come out of it's mounting in the thermostat housing. The housing is corroded and the groove cut in to hold the t-stat o-ring is pretty much not there anymore. The t-stat and o-ring fell out and were lodged in the upper water passage of the intake manifold. Luckily I was able to get them out and they were not ingested by the engine. Other than the problem I had, a bad gauge or sender, the most likely other thing could be a bad t-stat that would result in a cooler than normal operating temp. Good Luck!

 

[Z71Man]

Re: Volvo Runs Cool

All,
Thanks for the replies. Johnbo called this. I removed the 'stat housing and sure enough there was a small piece of impeller lodged in the passage he referred to. It wasn't blocking the hole completely, but was blocking a lot of it. It wasn't easy to see as it had taken on the same color as the surface corrosion of the inside of the housing. I removed the chunk with a coat hanger and put it all back together. The engine now comes up to 160-170 on the gauge and stays there regardless of operating condition.

Thanks for the help!

 

[Coors]

Re: Volvo Runs Cool

might be time to back-flush; more little pieces of gremlin still in there.
(I had 8 pieces).