Chevy 350 Engine coolant

Discussion in 'Inboards' started by mikealston2428, Oct 8, 2016.

  1. mikealston2428
    Joined: Jul 2011
    Posts: 188
    Likes: 0, Points: 16, Legacy Rep: 10
    Location: aussie

    mikealston2428 Senior Member

    Hi all
    Ok so I've removed the thermostat and it is a 70 degree one
    Im replacing it with a 60 degree one
    I've pulled all the salt water plumbing and found about 4 small pieces of impeller rubber in the inlet to the main exchanger none in the pumper steering cooler tho
    The main exchanger has a filter with hundreds of holes about 5mm in diameter but i don't think any impeller rubber has passed thru as the pieces I found where to big but can't be sure

    I'm running break in oil in it at the moment but that shouldn't run any hotter than standard oil ??
  2. Barry
    Joined: Mar 2002
    Posts: 1,173
    Likes: 98, Points: 48, Legacy Rep: 158

    Barry Senior Member

    I noticed the brass elbow on the right hand side ( when looking at the front of the engine) of the outlet going into the exhaust manifold. This is the worst choice for flow restriction and creating back pressure.
    The water is coming out of the exchanger into a T then splitting right and left.
    I will cover off three types of elbows,
    1) a regular, or short L, this is a relatively tight turn but smooth radius
    2) a long elbow, this is a larger radius turn but still a smooth turn
    3) the brass L that you have installed. The flow strikes the back of the fitting, creates impingement-stagnation pressure, increases turbulence and back pressure to the upside stream flow.

    So your cooling water comes to the T, and sees a higher backpressure situation on the right hand side. Therefore more water will go out the left side than the right side.

    Additionally, I expect that if you take the hose off the barb and measure the ID of the fitting, it will be significantly less than the ID of the hose as brass elbows generally have a thicker side wall thickness

    The higher the flow rate, the higher the back pressure

    It MIGHT not be too important but the end result will be a higher temp running right hand side exhaust manifold

    I would find a PREFORMED large sweep piece of hose from a automotive rad store, and put in two couplers, better a tubing style coupler, ie thin wall, large id to cure this possible problem

    You will have an idea of the amount of rubber that came off the disintegrated impellor.
    If you think that you have recovered all of what went down the hose, then you could there might not be a restriction from debris

    If with the 160 degree thermostat, you still have a high reading with this thermostat. Remove the thermostat completely and see what temp that the water is going into the block at.

    If the temp sensor is correct and the water that is coming out of the header tank into the engine is in fact 230, you should be able to just pour a little water on the top of the header tank and it should boil - steam off. Perhaps your sensor is giving you and incorrect reading

    Just a reminder
    The water that is coming from the circulating engine mounted coolant water pump should be entering into the bottom of the heat exchanger or you will not have proper cooling. IE the heat exchanger must flood from the bottom and the cooler water taken off the top to go back to the engine

  3. mikealston2428
    Joined: Jul 2011
    Posts: 188
    Likes: 0, Points: 16, Legacy Rep: 10
    Location: aussie

    mikealston2428 Senior Member

    Hi Barry,
    Some fantastic stuff there thanks.
    I will definitely remove the brass elbow and re-plumb as per your recommendation
    I am starting to think i may have a faulty sensor or gauge so i will look into this

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