Water pressure gauge location (revisited)

[dnyhuf]

After much forum reading, I installed a Teleflex gauge on my 92' 200GT. Most everyone on the forum, and Teleflex directions that came with the gauge, said install on adapter plate. So...thats what I did. Well, the result was a gauge that would not read any pressure until about 3000 RPM, and would top out at 8 psi at WOT. Teleflex website said my motor should read between 6-12 psi, so I thought my readings were normal. Well...to make a long story short, I recently replaced water pump, and thought I would play with the gauge, so here are the results.
Gauge installed on plate=no idle pressure, 8 psi at Wot.
Gauge installed on telltale=5 psi at idle, 14 psi at Wot.
As a side note....there are 2 water lines going to telltale, one from port side of block, and one from control valve on starboard side of block. I put a tee on port side line.
Question...can anyone tell me why it is recommended to install on adapter plate, considering these results?

 

[Dhadley]

Re: Water pressure gauge location (revisited)

If you T'd into the line from the adaptor plate to the water control valve, that is correct. It sounds like you T'd into the crossover line. That will work but reads pressure at the top of the block, not the incoming pressure. The whole idea of reading incoming pressure vs. exiting pressure is to know what's going to happen rather than what's already happened.

There is another plugged hole in the adaptor plate forward of the line going to the control valve. That hole is used on models with power steering. You should be able to use that hole too.

Sometimes an aftermarket gauge will read differently that an OE gauge so it's really hard to base one on the other. You can also use the late model style water pump kit rather than one for a 92 model. That should up the pressure a bit too.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

The original hookup on adapter plate was on the plugged hole in front. Hard to believe that teeing into the control valve feed behind it would give any better reading, but have not hooked up there, so can't say for sure. So yes, it is tee'd at exit point of block.
I have discussed this with you before Dale, and have considered your theory of gauge differences as an explanation. Are'nt all pressure gauges calibrated the same regardless of brand, application, etc., after all psi is psi, no matter who made the gauge.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

How can different brand gauges read differently? The laws of physics demand that a pressure gauge made by manufacturer A read the same as manufacturer B. Also, Can you explain why it makes a difference where pressure reading is obtained. If you lose pressure, hasnt pressure been lost throughout the whole system.

 

[Dhadley]

Re: Water pressure gauge location (revisited)

There's no reason that the hole in front (used for power steering) shouldn't have worked. We've used it many times. Perhaps there is a restriction in the adaptor plate.

In theory all pressure gauges should read the same, unfortunately they don't. It's just something we run into from time to time.

Reading incoming pressure really tells us what the pump is doing. If it goes down we know something is going on below the powerhead. If it goes unusually high we know we have a blockage in the powerhead. Both can result in an overheat.

Reading exiting pressure tells us what is going on behind that point. If it goes down we have a weak or clogged pump or a clogged passage. Low pressure readings could also come from a missing t-stat.

Reading the pressure in either place has it's advantages and disadvantages. We simply try to keep the fitting in the place OMC / BRP intended do we're comparing apples to apples.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

Thanks, that makes sense.:redface: So...a possible restriction in plate. Looking at the water flow chart in the OEM manual, it appears that the plate may be separated into a front and rear section, if that is the case, could a restriction be in the front half only? Would that explain the low reading from the plate? Also if half of plate were resricted, would that explain the higher reading at telltale, back half of plate still open? Should I check pressure at rear of plate to control valve?

 

[Dhadley]

Re: Water pressure gauge location (revisited)

Sure, the gauge was intended to read at that point on that motor. Just curious, if you take the allen plug out of that forward hole and start the motor, does any water come out? If not maybe we could blow air in there to see if we dislodge anything??

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

I'll try that this afternoon, and post result's. Thank you for your patience with my never ending questions.

 

[Dhadley]

Re: Water pressure gauge location (revisited)

No problem, this is how we all learn.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

Ok...now I'm really confused. Checked for restriction in forward plug on adapter plate. No water came from that plug, but plenty of exhaust did. Shot a blast of air in it, and nothing. Pulled water line from control valve and started motor (on muff's). Good solid stream. Moved gauge line from telltale to control valve inlet, and hear are results.

Gauge line T'd to telltale = 5psi at idle
Gauge line T'd to control valve = 8-10psi at idle

 

[Dhadley]

Re: Water pressure gauge location (revisited)

That's what we're used to seeing on that style motor. And since there's a water control valve, the gauge will jump around if you rev it up momentairly in neutral once the gauge is T'd into that line.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

What about the exhaust coming from forward plug? Did you not say that should be water also?

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

ttt

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

?????

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

"There is another plugged hole in the adaptor plate forward of the line going to the control valve. That hole is used on models with power steering. You should be able to use that hole too."


"There's no reason that the hole in front (used for power steering) shouldn't have worked. We've used it many times. Perhaps there is a restriction in the adaptor plate"

"Sure, the gauge was intended to read at that point on that motor. Just curious, if you take the allen plug out of that forward hole and start the motor, does any water come out? If not maybe we could blow air in there to see if we dislodge anything??"

All of the above qoutes lead me to believe water should come from the front hole on adapter plate. Can anyone explain why exhaust would exit there. anyone...............

 

[Dhadley]

Re: Water pressure gauge location (revisited)

I'm not really sure why yours doesn't have water and the couple of ones we used did. Maybe we were working with different years, I'm sure they were't XP / GT's because they were 25" models.

 

[dnyhuf]

Re: Water pressure gauge location (revisited)

I'm not really sure why yours doesn't have water and the couple of ones we used did. Maybe we were working with different years, I'm sure they were't XP / GT's because they were 25" models.

Thought I would update everyone after researching this further. The front plug on these loopers IS used for power steering ONLY. That is a combination Exhaust - Water port. NOT suitable for water psi gauge. The ONLY place recommended for psi gauge is at control valve line located at rear of plate.
Sure hope this clears things up for all of you that use the search function as much as I do.