Running Hot

[champ]

Never had a problem with overheating before, but this year all has changed. I started out the year changing the thermostat in my ford 351 Windsor. I went from a 180 degree to a 160 degree to see if there was a difference.

Running of a garden hose everything seemed well. Took her out on the water, idling around she ran at about 180 degrees. After a good run, the temp started climbing to a good 200 or so.

Time for a new crank driven water pump I thought, threw one in her. Temp still kept climbing. New water circulating pump, still hot. Pulled the thermostat out, just to flush the salt water out, it ran cool on the hose at about 120 degrees or so.

Here's what I did next. After searching on this site I read that using a candy thermometer in a pot of hot water is a good way to check a thermometers accuracy. Got the water to about 170, dropped in the thermostat and waited for it to open. What a surprise it was to see it pop open causing a wake in the pot of hot water.

Seems there is a rough spot or snag in the function of its opening ability. It is a sierra, so I don't want to buy another one of them. So while I have it out I was curious as to if I should stick with a 180 like I had and to what brand would anyone recommend? Also, would drilling any holes through the new one have benefit as far as purging any air out of the system or allowing less restriction of the flow.

Appreciate any advise.
Thanks

[smokediver]

Why did u replace the old one ? If you have a temp probe going into the side of the water pump housing and it is a different t stat the probe could be catching the spring. That happened to me. I would put the old one back in.

[mattyboy]

Never had a problem with overheating before, but this year all has changed. I started out the year changing the thermostat in my ford 351 Windsor. I went from a 180 degree to a 160 degree to see if there was a difference.

Running of a garden hose everything seemed well. Took her out on the water, idling around she ran at about 180 degrees. After a good run, the temp started climbing to a good 200 or so.

Time for a new crank driven water pump I thought, threw one in her. Temp still kept climbing. New water circulating pump, still hot. Pulled the thermostat out, just to flush the salt water out, it ran cool on the hose at about 120 degrees or so.

Here's what I did next. After searching on this site I read that using a candy thermometer in a pot of hot water is a good way to check a thermometers accuracy. Got the water to about 170, dropped in the thermostat and waited for it to open. What a surprise it was to see it pop open causing a wake in the pot of hot water.

Seems there is a rough spot or snag in the function of its opening ability. It is a sierra, so I don't want to buy another one of them. So while I have it out I was curious as to if I should stick with a 180 like I had and to what brand would anyone recommend? Also, would drilling any holes through the new one have benefit as far as purging any air out of the system or allowing less restriction of the flow.

Appreciate any advise.
Thanks

didn't you just take apart the steering fork? did you replace the water seals? water pickup is in the Volvo drive? or do you have an external water pickup?

if the drive is the water pickup and the seals in the water pickup are shot you suck in air when on plane when off plane the seals are in the water and no air gets in. if you can let her run at idle in the water then put around at idle speed for any good period of time with no rise in temp but once you plane off the temp climbs the system is getting air in it another possibility is the hose for the intake from the drive to the transom housing or from the transom housing to the pump is collapsing when under load

[Lenny]

Great reply Matty ! Never thought about that.

[champ]

didn't you just take apart the steering fork? did you replace the water seals? water pickup is in the Volvo drive? or do you have an external water pickup?

if the drive is the water pickup and the seals in the water pickup are shot you suck in air when on plane when off plane the seals are in the water and no air gets in. if you can let her run at idle in the water then put around at idle speed for any good period of time with no rise in temp but once you plane off the temp climbs the system is getting air in it another possibility is the hose for the intake from the drive to the transom housing or from the transom housing to the pump is collapsing when under load

Hi Matty,
I do have an external pickup. And, am still working on the steering fork issue that is on the outdrive I planned to swap. I ended up rehanging the old outdrive onto the boat just to get out on the water.

Of the things you mentioned, they were on my list as it was puzzling to think what could be keeping it hot. Especially air in the system. This was why I was asking about a hole or holes drilled into the thermostat.

Still would like to know what you or others think about that, and what temperature to use while I have it out? Also while I am asking, is there a difference between brass and stainless? And a brand that is either a high flow or of better quality than Sierra?

[mattyboy]

ok that eliminates the seals in the drive.

I never run a Tstat both of my HM fords had their crossover system with one crank driven pump and no t-stats

I may be tough but it sounds like it only gets hot when running above idle run without the hatch and have a buddy look to see if the intake hose is collapsing under load.

both of my setups would "false over heat" after a hard run coming off plane the temp would spike to around 200-210 for a brief moment then come back down to the 180 -190 it would run with mid 70s lake water this was said to be normal for a raw water setup. If the seals were bad it starts to climb and keeps going up the longer you are on plane and as soon as you come off plane the temp starts to come down

how are your risers? if they are loaded with scale and rust they may reduce flow I had one totally block on me at lake george the motor didn't overheat but the temp did rise and the exhaust hose started to burn

you have two pumps is it still a fully open raw water system or is it a full or 1/2 closed system?

the holes are to allow some flow of coolant around or thru the tstat until the tstat opens on the HM crossover if there is no flow of coolant coming past the tstat your are going to fry your exhaust hose their tstat housing has a bypass hole. the only water connection to the riser is from the tstat. on the CC chevy setups they had bypasses that pumped raw water directly to the risers not from the block and in some case pumped raw cold water into the dump of the riser as well

I would run with out the tstat and see if anything changes

[woobs]

A possible fault (while not a pleasant one) you may want to consider is a cracked head or failed head gasket.

Upon rebuilding my woody boat in 2012 we re-installed the motor which had been running perfect previously. It was winterized and stored indoors. The boat started easily and ran fine at idle yet, when under load or on plane it would overheat in just a couple of minutes.

Thermostats, impellers, manifold change, new hose, new head gasket... nothing worked. I finally upgraded to a new engine but, a post mortem found a small crack in the old head. this crack expanded under heat/load to cause the overheating.

[Pat McPherson]

I'm not a Ford guy so I'm not show how the T-Stat housing is configured. How about running without the T-stat to check if there is a water flow issue?

Just reread Matt's post... I guess great minds...

[champ]

So on my set up, I am not using the H/M crossover. I have in its place a stock ford water pump in its place. So, yes I am using two water pumps. and, it is all raw water. I do have the H/M tstat housing so there is a bypass to wet the manifolds.

I have also checked for collapsing hoses and plenty of water is exiting the exhaust. Another concern was this: having two new pumps installed and with the crank pump being the larger high flow Johnson, could there be too much pressure in keeping the thermostat closed?

Today is Friday, gonna try running with out a thermostat, and then putting the first one back in maybe with a hole drilled in it if the temps aren't right without one.

Thanks everyone for all of your thoughts.

[tmdog]

As a by pass for flow, drill three 1/8 holes in thermostat.

[gcarter]

I installed a T-stat backwards once. It doesn't work that way.

[mattyboy]

I installed a T-stat backwards once. It doesn't work that way.

that was my other thought

[mattyboy]

So on my set up, I am not using the H/M crossover. I have in its place a stock ford water pump in its place. So, yes I am using two water pumps. and, it is all raw water. I do have the H/M tstat housing so there is a bypass to wet the manifolds.

I have also checked for collapsing hoses and plenty of water is exiting the exhaust. Another concern was this: having two new pumps installed and with the crank pump being the larger high flow Johnson, could there be too much pressure in keeping the thermostat closed?

Today is Friday, gonna try running with out a thermostat, and then putting the first one back in maybe with a hole drilled in it if the temps aren't right without one.

Thanks everyone for all of your thoughts.

not sure on the two pump setup doesn't the coolant flow push against the spring in the tstat and as the spring heats and weakens the flow compresses the spring more allowing increased flow? but too much pressure can cause bad things, like the thing that woobs mentioned head gaskets blowing did you check the oil?
I am hoping that as you read this no tstat fixed the issue

[woobs]

...the coolant flow push against the spring in the tstat and as the spring heats and weakens the flow compresses the spring more allowing increased flow?

That's not how a thermostat works. If you were to put a t-stat on a wire and suspend it in a Pyrex beaker of water, then bring it to boil on a heater element, you would see the opening action independent of flow or pressure. Using an accurate thermometer, you can see how accurate the thermostat is. Likewise, as the heat is removed and the water cools the T-stat also closes without flow present and you can judge performance by the thermometer.

Closed automotive systems run 15-18 psi. Any more and you have other issues. Afaik, open marine raw water cooling systems do not run anything close to this... how could they? (they are not sealed). It is my understanding that water pressure in these marine applications is directly related to the ability/strength of the pump(s).

Our family owned a chain 36 of radiator/cooling system repair shops.... I used to do this exact thermostat test 10 times a day for several years as the failure rate for new t-stats was in the 30% range. (Eventually we just changed suppliers and the failure rate dropped to 2.5-3%)

Here's a long winded (but decent) You Tube explanation of t-stat operation... https://www.youtube.com/watch?v=-UOQnitRtOc

[mattyboy]

That's not how a thermostat works. If you were to put a t-stat on a wire and suspend it in a Pyrex beaker of water, then bring it to boil on a heater element, you would see the opening action independent of flow or pressure. Using an accurate thermometer, you can see how accurate the thermostat is. Likewise, as the heat is removed and the water cools the T-stat also closes without flow present and you can judge performance by the thermometer.

Closed automotive systems run 15-18 psi. Any more and you have other issues. Afaik, open marine raw water cooling systems do not run anything close to this... how could they? (they are not sealed). It is my understanding that water pressure in these marine applications is directly related to the ability/strength of the pump(s).

Our family owned a chain 36 of radiator/cooling system repair shops.... I used to do this exact thermostat test 10 times a day for several years as the failure rate for new t-stats was in the 30% range. (Eventually we just changed suppliers and the failure rate dropped to 2.5-3%)

thanx for the explaination so it is the thermal device that doesn't get heated up if you put it in backwards because the heat source the coolant is on the other side so it never really lets it open?