How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

[Deep_Blue]

I want to install a water pressure sensor for my Merc 90, it doesn’t even have to be in PSI just some sort of flow sensor that won’t disturb the natural function of the cooling system. I love my engine too much to take the chance of running it dry due to some small clog or impeller failure.

 

[gss036]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

The only thing you can install is a water pressure guages. It is an inexpensive item for a kit and well worth the efffort.
Go over to the TelFlex site and look at their articles on how to install gueages.

 

[Silvertip]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Heck, you could use an oil pressure switch and an idiot light if thats all you are after. Most of those turn on at or about 6 PSI so anything less than that would light a lamp on the dash. But why bother, a water pressure gauge is cheap and simply "Tees" into the telltale. Change the water pump at the same time so you know what "normal" is. Any future deviation tells you something is amiss.

 

[Bob_VT]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

On my inline a water pressure gauge is all I have, the previous owner installed it and the tell tale is dis-connected. I swear by the gauge..... it just saved my engine a few days ago.

 

[jnewtonsem]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Is this an old In-Line? If so, there is a hexscrew on the back of the block between the 1-2 cyl. Unscrew the screw and replace with an L screw and run a hose to the gague on your dash. Tell-tale will still work. Note: the in-lines do note have as high a WP as newer mercs. at idle needle will barely move. At full throttle will measure about 7PSI.

 

[Deep_Blue]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Oh yea, I do remember seeing that. cool that makes it real easy to do. but i was wondering, wouldnt the pressure be higher right after the impeller? still thanks though.

 

[jnewtonsem]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Probably, but on the Merc thegauge is measuring pressure reaching the top cyl, basically the farthest point from the intake. When the cooling system fails on in-lines it is almost always the top cyl that gets damaged. So the gauge is really measuring PSI at your most critical point. As far as install- the telex has all the proper fittings. Real easy to install. Even an idiot like me can do it.

 

[Deep_Blue]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

good point jnewtonsem

thanks

 

[Deep_Blue]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Ok, i just bought a water pressure switch that is adjustable from 1-25 psi, looks like this:

Think that might work ok?

 

[Silvertip]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

And at what pressure will you set it? Water pressure on most engines will vary from as little as 2-4 PSI at idle to as much as 15 - 18 or more at WOT. The point of a water pressure gauge is not so much "what" the pressure is but more "has it changed from normal". No two engines will run exactly the same pressure. The idea is to install a gauge and a new water pump at the same time. Note wide open throttle and idle readings. These are your "new impeller - normal reference". Any deviation from this in the future means the water pump is in need of attention. Your switch will work, but what do you want it to tell you? If its set on the low end, you may get an OK indication but at high RPM the engine may indeed be short of water. Set it for the high end and it you will have a constant "bad" indication at anything less than the high setting. Nice idea, but it's not a valuable indication in my view.

 

[Deep_Blue]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Very true, but with the knowledge that it is for those high rpm moments ware you really don’t look back at your engine, I think a red light would be adequate enough for my setup. I just want an easy quick and cheap setup for now. But you do make a good point as I was originally going to set it for idle pressure. Thanks Silvertip. I will however get a gauge when I buy a gauge set. I don’t even have a speedometer right now but I try to install a few new toys every weekend!

 

[Deep_Blue]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

Ok now I know im getting complicated and I should just get a gauge, but I think a light and buzzer would be nice + I already have all the parts.

So I may place a roller switch some ware on the throttle cam (like when the spark advance kicks in) that will allow the light to function. The pressure switch will be set just a little under that rpm/pressure. If throttle is lower then the advancing point the circuit has no power. And you could tie in a 10 second delay relay that kills the engine as well.
Sounds easy, and think of that in conjunction with a gauge. A little redundant but you cant run your engine without water

automatic engine kill... i like that!!!

 

[Silvertip]

Re: How Can A Water Pressure Sensor Or Flow Swithc Be Installed?

For the price of the system you are trying to build, you can have a water pressure gauge. Actually, the engine is can overheat due to water flow problems at idle or WOT depending on what the cause is. The best combo is a temp gauge, water pressure gauge, and functioning overheat warning. If you want a warning light, finding a temp switch (not thermister) calibrated for about 175F could be used to signal an overheat "in progress" before the actual overheat horn goes off. That would provide advanced warning that something is amiss. That coupled with the gauges tells you how serious the situtation is becoming rather than what's actually happened (which in many cases is way to late to prevent engine damage.)