Coolant Blowing out Overflow Pipe

[Winnebago73]

The radiator has been flushed out - engine too, new caps and 50/50 coolant added. Why does it always blow water out the drip pipe? It reaches 190° but still blows excessive coolant out. Can you suggest what could be the problem?
Thanks
Kurt

[DaveVA78Chieftain]

Sounds like you have a 16psi coolant recovery style radiator cap but no coolant recovery tank.  The pre-73 M300/M375 chassis used a 7psi cap that was not a coolant recover style.  Only vented out if internal coolant pressure exceded 7psi.  The RM300/RM350/RM400 chassis changed to a 16psi coolant recovery style system and  cap.  This type of cap allows the system to vent off some water as it heats up until a certain temp is acieved then holds at that point.  It will only vent more off if the system exceeds 16psi.  As the engine cools down, a vacuum is created in the cooling system and the cap allows coolant to be sucked out of the resevroir back into the radiator.  Maintains system water level this way.

If you are using a recovery style cap, then add a coolant recovery tank.

Using pure distilled water the boiling point is raised 3 degrees for every one pound of pressure the cap is set for.

7psi = 212 + (3x7) = 239 degrees

16psi = 212 + (3x16) = 260 degrees.

A 50/50 antifreeze mix raises it about 7%

239 x 1.07 = 256

260 x 1.07 = 278

Dave

[Winnebago73]

Yes I have a 16psi cap two in fact, no reservoir tank just a drip pipe. Do you think I should take out the 50/50 and put distillers water only ? Or should I run a 3/4 galvanized pipe from the original take off to the back of the chassi and back into the return. Before there used to be water pipe running to the water heater positioned in front of the back wheel. It was rusty so I capped the two robber take off and return under the thermostat manifold ?
Kurt

[DaveVA78Chieftain]

Being in FL you could delete the antifreeze however look at my previous post about how the antifreeze increases the boiling point by 7%.  By removing it you will hit that 16psi limit at a lower temperature.  Besides, you will STILL LOOSE fluid.  The design of the cap allows fluid to go back and forth from the resevoir to radiator by design.  Just get yourself one of these kits from your local auto supply house:
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Coolant-Return-Kit-for-Larger-Size-Vehicles-Interdynamics_6010253-P_N3052_A%7CGRP2014___

Be sure to get the 2 1/2 qt model BVR-4 not the smaller 1 1/2 qt MCR3 model.

Dave

[Winnebago73]

Dave you have been such great help. I am glad and very thankful for meeting someone with so much knowledge in helping me with this.
All the best
Thanks friend
Kurt

[ClydesdaleKevin]

One other bit of advice here though.  Whenever you disconnect coolant lines that lead to a system, be it a water heater for the coach or even the heater box under the dash, you should never just cap off the lines.  Using new hose just long enough, you should "close the loop" rather than cap it off.  In other words, push the new length of hose on the outlet that the long coolant lines used to come off of, push the other end on the inlet fitting, and secure it with hose clamps.

If you just cap it off, you run the risk of a coolant blockage to parts of the engine and can overheat parts of the engine, whereas if you close the loop, you haven't changed the flow of the coolant at all and the coolant system will work as designed, reaching all of the engine as engineered by the factory.

Kev