D8H Dozer water pressure gauge problem.

[Mopar Mark]

The engine runs cool but the water pressure gauge keeps rising high in the yellow. Radiator is full and you can touch the antifreeze and it's not hot. Pulled the relief valve next to the radiator cap and cleaned it. Could it be the thermostat in the relief valve ? Any ideas why it keeps going up?
Thanks

 

[kshansen]

Been a few years since I touched one those, does the gauge have actual numbers on it besides the colored bands?

Believe the relief valve is stamped with the pressure it is set for so might be good to know what it says.

You say the antifreeze is not hot, is this after the machine has been working and the pressure gauge is going up? What does the temperature gauge say, I'm assuming it has on in addition to the pressure gauge.

One other thing that sounds odd, you mention "the thermostat in the relief valve" not understanding what you are referring to there, aren't the thermostats (Cat calls them regulators) in the front end of the water manifold?

And a couple more things that may be of help to know, first off as always a full serial number and then how new a problem is this and how long have you had the dozer.

 

[Mopar Mark]

The gauge is only colors Green/Yellow.

The machine itself doesn't run hot. The water is only warm after it has been running a while. Temperature gauge is great.

A few hours ago after I posted this It was very high . I loosened the radiator cap while it was running and tightened it back. It hasn't gone back up yet after about 3 hours run time. Possibly a air blockage?

The relief valve that is next to the radiator cap is a bolted cap that when you pull it out has what looks just like a thermostat.

Serial # 46A27812

I Have owned it a couple of months and this has been an issue since I bought it.

 

[Delmer]

If you're not losing coolant, then I don't think there's anything wrong. The coolant should be hot, like 160-190, if you can touch it there's something wrong with the thermostat, or is the opening you're touching the cool side of the radiator?

Also, if you don't have an expansion tank on the cooling system, then the level should not be full, it should be below the bottom of the filler neck to leave some air space for expansion of the coolant.

 

[Mopar Mark]

actually taking off the top and putting fingers in the coolant it is not hot enough to burn you . My son suggested the same thing about the thermostat when we discussed it earlier. He thought maybe the thermostat is stuck open so the water is not getting hot enough to build pressure for the relief valve to function properly. What do you think?

 

[John C.]

Get an infrared thermometer and check the temperature on the water manifold before you do anything else. Pressure in the radiator is one of two things, normal expansion of the fluid because of heat. I don't think you want to know what the second possibility is.

 

[Rusted]

The engine runs cool but the water pressure gauge keeps rising high in the yellow. Radiator is full and you can touch the antifreeze and it's not hot. Pulled the relief valve next to the radiator cap and cleaned it. Could it be the thermostat in the relief valve ? Any ideas why it keeps going up?
Thanks

From my memory of running 8H's back in the day, the water pressure being high in the yellow is perfectly normal, even desirable, as if you correlate it to the similar color coded temp gauge it allows you to run at a higher temp before going into the red. We used to avoid removing the rad cap when the engine was hot because they wouldn't build the pressure back up afterwards, giving you a lower overheat temp on the color coded gauge. (I'm assuming here that your machine still has the correct temp gauge with the same colors as the pressure gauge).

 

[Rusted]

View attachment 200515 Found a pic of the original temp gauge.
View attachment 200515 View attachment 200515

 

[Rusted]

Ooops...sorry for the double post.

 

[Rusted]

Try again.

 

[56wrench]

I agree with Rusted. my 46a although it is the low-horse model has the same water pressure and temp gauges. if it won't build any pressure then the relief is stuck open or you have a leak. in this case, pressure is what you want. no pressure=possible problem. too much pressure(at the high end of the red)also = possible problem. pressure allows you to load the engine harder without boiling coolant out the relief. by raising the coolant pressure, you raise the actual boiling point of the coolant. if memory serves me right, 1 psi=1 degree higher

 

[56wrench]

oops, I should have said-highest end of the pressure gauge

 

[56wrench]

actually, I just found this in an original CAT operator's guide for D7,D8 and D9 tractors. I quote " if tractor is equipped with water pressure and water temperature gauges, both gauges should register in the same color ranges. do not operate when temperature gauge indicator is beyond color range indicated by pressure gauge. the tractor may be operated if pressure gauge indicator is beyond color range indicated by temperature gauge."

 

[kshansen]

So if I am understanding the way both gauges relate to each other it would be this:

If pressure gauge is in the "Green Zone" then when looking at the temperature gauge you would use the area that has the green stripe to determine how hot is the "Safe Operating Temperature"

If the pressure gauge is in the "Yellow Zone" then the "Safe Operating Temperature" would be determined by looking at the upper part of the scale that has the yellow stripe.

This makes sense, at least to me, as the higher the pressure on the coolant the higher the boiling point of the coolant.

And as John C. says "Get an infrared thermometer and check the temperature on the water manifold before you do anything else. Pressure in the radiator is one of two things, normal expansion of the fluid because of heat. I don't think you want to know what the second possibility is."

Those thermometers can now be had online for as little as $12.00, may not last as long as the more expensive ones but should answer any questions at this time.

 

[nicky 68a]

Hello.
If your D8 is not running hot in the engine after a days work without it spewing water out of the relief gauge,them go to the pub,have a beer and relax.
Those water pressure gauges cause more bother than they are worth.
I suggest you remove the gauge entirely and throw under the nearest track pad.
You'll know when you have pressure problems in a D8 soon enough.

 

[nicky 68a]

On another note,only put enough coolant in them so it covers the fins and nowt more

 

[kshansen]

Hello.
If your D8 is not running hot in the engine after a days work without it spewing water out of the relief gauge,them go to the pub,have a beer and relax.
Those water pressure gauges cause more bother than they are worth.
I suggest you remove the gauge entirely and throw under the nearest track pad.
You'll know when you have pressure problems in a D8 soon enough.

I like the way you think nicky!

Often wondered why the only place I had ever seen one was on an old D8 or 9. Last I knew somewhere on a shelf at the quarry there was a brand-new one of those pressure gauges still in the box.

Kind of wish I had made the "mistake" of slipping it into my tool box before I retired, as a curiosity item. I know no one there now would have the faintest idea what it was used in!

 

[Tinkerer]

Hello.
If your D8 is not running hot in the engine after a days work without it spewing water out of the relief gauge,them go to the pub,have a beer and relax.
Those water pressure gauges cause more bother than they are worth.
I suggest you remove the gauge entirely and throw under the nearest track pad.
You'll know when you have pressure problems in a D8 soon enough.

This reminds me of when I ran a service truck. Operators calling me to change fuel filters because the pressure gauge was showing low pressure. The worst were D9Gs.

 

[nicky 68a]

I like the way you think nicky!

Often wondered why the only place I had ever seen one was on an old D8 or 9. Last I knew somewhere on a shelf at the quarry there was a brand-new one of those pressure gauges still in the box.

Kind of wish I had made the "mistake" of slipping it into my tool box before I retired, as a curiosity item. I know no one there now would have the faintest idea what it was used in!

I still have one on the shelf,and that bugger was given to me by somebody else that didn't want it either!!!