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pressurize or not?

matuva

matuva

Tropical 6.5er
Messages
1,996
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21
Location
New Caledonia. An island in south west pacific, cl
Was debating today with my mechanic.

He is used to drill a small hole in the surge tank cap - about the size of a match stick or tooth stick - so as to release pressure in cooling system
by venting it to atmosphere.

The fact is that the trucks are really less prone to overheat that way.

Though, I'm wondering if this pressure is needed or not :???: After all, if GM engineers have designed cooling system with pressure, should it stay pressurized or not?
 
Yes,

The pressure increases the boiling point so the hottest spots are less likely to have localized boiling. The average temp of coolant might be well below boiling but inside the heads can be much hotter.
 
:iagree: The pressure is required!

The localized boiling is what cracks the heads.

A clean system inside and outside, proper coolant concentration does more to keep things cooled than anything. The rest of the system is important, but the radiator core is easily and often overlooked.

A radiator sprayed with degreaser, leaned against a car wash bay and 10 minutes of Hot soapy high pressure water from both sides goes really far in solving over heating.

I did this and could not believe the bugs and crud still floating away on the floor after 5 minutes of washing.

After years of cleaning radiators of farm equipment, you can not believe the amount of crap that can hide within a radiator core!
 
Sell a lot of caps after they fail the pressure test I bet. Ruin a lot of water pumps from the suction creating steam bubbles to try and pump? Boiling point of water is 212 degrees. So after it boils out of the coolant (at a higher temp than 212 degrees) it needs to see a place lower than 212 degrees to condense. Why? Because after it boils it is pure water - not a mixture. Add pressure to raise the condensation and boiling temps.

The thermostat is full open at 205 degrees. Other parts of the engine may need more than 7 degrees to keep from boiling. Even a pressurized cooling system will generate lots of steam bubbles and this little known fact is why water wetter works.

No pressure you need Evans waterless coolant. Otherwise you are turning the engine into a boiler. Steam bubbles forming also erode metal.

I wouldn't get very far with a bad cap like that without the low coolant light on or vapor locked water pump as the grades here work even unloaded vehicles.
 
Hey google racing radiator caps. We have 2 choices. 24-28 psi or 28-32 psi. Pressurizing the system does what is said above. It raises the boiling point greatly. Being hot isn't what hurts an engine. My corvair heat gauge read 200 to 600 degrees. It hit the high side on many o parades! Boiling causes hot spots. Not a little higher...a lot higher! 1200 to 1600 degrees in a heartbeat once boiling starts. Its those temps that burn head gaskets and other parts. Nascar has been running coolant pressure gauges for a couple years and us smaller classes are starting to as well. With that we see an issue before the temp gauge rises!
 
On one of my marine diesel engines I had a period where it ran hotter than spec. 200 F vs 194 F. Went through everything trying to address it. Finally discover that the sealing flange on the brass coolant overflow reservoir was bent upwards, preventing one side of the cap from sealing. Bent the flange back with some pliers and the temp dropped back within spec. So I was running without proper pressure in the cooling system. That pressure is very much needed.
 
That is what I run in mine, You have to account for the time that the radiator needs to shead the heat. It itsnt instant. the water has to flow back thru the motor to the rad to have the heat removed.
If you start with a 190, it only gives you 10 degrees for the system to remove the heat, which is not enough time for the HIGH BTU's that these engines create under a load.
 
175 in mine solved a lot of issues. Hard to find though! I have a parts store I can raid boxes in. The one that fit at 175 was for some Honda!
 
Keep in mind that Diesels require a certain amount of heat to run efficiently, for best mileage. Diesels are heat engines, there is a relationship between, what I'll call base temp and compression temperature. You see this in the extreme at start up and having a bad glow plug. The white smoke you see is unburnt fuel from the cylinder being too cold. It clears at the cylinder come up to temperature.

You should not run Diesels too cold. 180 to 190 has been recommended for the 6.5. No one, I've seen, has published a definitive mileage trial to prove the best temperature for the most efficient operation on the 6.5.

I run a 190 tstat, in 100 degree weather and 5000lb trailer under very hard acceleration, yes it spikes past 210. But having the fan clutch modification to drop the engagement temperature brings that temperature right back down.

I carry a snow plow at times. At 70mph, the blade diverts enough air to create a vacuum in front of the radiator and cause the temperature to rise. Before the fan clutch modification the engine could see 215 or 220 if it was not monitored correctly. After the modification, the fan kicks in and I can see just over 210, unless the plow blade is 1 inch off the pavement.


There are plenty of posts and documented experiences, experiments, and procedures to improve the cooling capacity of the 6.5. Some really good, some just PLAIN STUPID!

Water wetters
Specific water pump versions
Specific fan clutches
Modification of fan clutch engagement
Dual thermostats
Blocking plate bypasses
Specific fan blades
Additional (electric) fans
Cleaning components
etc etc etc etc etc
 
I am trying to explain that to my brother who has a 160wasted in his dmax. I was running the 185 but it kept getting warm when towing in high heat. I was looking for something lower that would fit but not too low. The 175 was just what I found. It worked.
 
countryboy69 said:
I am trying to explain that to my brother who has a 160wasted in his dmax. I was running the 185 but it kept getting warm when towing in high heat. I was looking for something lower that would fit but not too low. The 175 was just what I found. It worked.
Click to expand...

Teh DMAX uses a 180 and a 185 in stock form, and is designed to run in the 200-220 range. And going to a lower temp T-stat does NOT prevent overheating, it only makes it take longer until it gets as hot. If an engine will hit 220 with a 195, it WILL do it with a 180 or a 160 just as easily as they are ALL fully open before 220. By running a lower temp T-stat you are only making it take longer to get to the hot temp, but you are adversley effecting a diesel by creating to low of a cylinder temp when running empty and costing yourself money. As said above, it takes heat to ignite diesel, so lowering your engine temp means it has to work harder to ignite it. You have a temp window teh engine wants to be in, run it to low and you get a poor burn, and run it to hot and you hurt the engine, but keep it in that temp range and she's happy.
 
I forgot to mention it was way cheaper! Lol hey thanks I am gonna send that to Buddy and see if he will listen. I know it but as redneck as I am its harder to get the belief!
 
countryboy69 said:
I forgot to mention it was way cheaper! Lol hey thanks I am gonna send that to Buddy and see if he will listen. I know it but as redneck as I am its harder to get the belief!
Click to expand...

I'm just as much redneck / hillbilly as anyone else, on top of that I grew up farming. Translated, "a cheap bastard". There's cheap and then there is stupid. Cheap can fix a lot of things pretty well, its been said that you can't fix . . .

Granted, I've also done my share of stupid stuff too. It's cost me a whole lot more than I care to admit. . . .

just saying
 
matuva said:
Was debating today with my mechanic.

He is used to drill a small hole in the surge tank cap - about the size of a match stick or tooth stick - so as to release pressure in cooling system
by venting it to atmosphere.

The fact is that the trucks are really less prone to overheat that way.

Though, I'm wondering if this pressure is needed or not :???: After all, if GM engineers have designed cooling system with pressure, should it stay pressurized or not?
Click to expand...

Sealed system Al we get every bit as hot as you do in South Ms maybe even hotter at times and even towing to 18K I don't overheat, clean system, working fan clutch, stats and caps as designed are all that are required to keep the engine properly cooled.
 
Turbine Doc said:
Sealed system Al we get every bit as hot as you do in South Ms maybe even hotter at times and even towing to 18K I don't overheat, clean system, working fan clutch, stats and caps as designed are all that are required to keep the engine properly cooled.
Click to expand...

Well yeah Tim, I will stick with my 1st idea and ordered a cap + a 190° T-stat from Robertshaw. My next Ted's engine swap is to make the most reliable Blazer I can. So I will build as close to specs it has to be.

BTW Tim, does your heath water balance make a noticeable improvement in cooling? What do you think of some setups which connect heads together by the rear port, then to the rad hose returning from cabin heater?

Thanks ;)
 
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