Monitoring coolant pressure with a sensor

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Monitoring coolant pressure with a sensor

Postby Pontisteve » Fri Jan 13, 2017 9:16 am

A tuner colleague of mine recently turned me on to a neat trick we use in drag racing. To use a coolant pressure sensor (or oil pressure sensor) in the cooling system to detect problems with the engine. Typically, we may be running a bit too much timing, and as the motor warms up detonation sets in. This begins to lift the cylinder head, and the sensor can pick up that increase in cooling pressure before the engine gets hurt.

I was wondering if anybody was scoping coolant pressure for diagnostic purposes, and had any luck with that?
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Re: Monitoring coolant pressure with a sensor

Postby Technician » Fri Jan 13, 2017 7:55 pm

On a lot of vehicles on public roads in the UK manufacturers seem to fit CHT sensors and my experience with those are that if the engine starts to overheat the ECM shuts off the fuel supply to prevent damage occurring until the temperature reduces to within normal operating range again. Anything off roads I have no experience in TBH. :)
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Re: Monitoring coolant pressure with a sensor

Postby STC » Fri Jan 13, 2017 10:06 pm

I was wondering if anybody was scoping coolant pressure for diagnostic purposes, and had any luck with that?


Yes and it does work. I have these Schrader valves which screw into my Coolant Pressure Test Adaptors (and whatever else I can get my hands on) I can then attach my pressure transducer to the valve.

Synchronised to Cylinder One I can see if Combustion Pulses are leaking into the Coolant system and identify the offending Cylinder(s).

All you need is a drill and a 1/8" BSPT Taper Tap.

Schrader.jpg
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Re: Monitoring coolant pressure with a sensor

Postby Technician » Sat Jan 14, 2017 1:57 pm

I have something similar to those which came in a snap on cooling system tester some 25 years ago, but have never thought about using any type of measurement from the cooling system other than using the pressure gauge and the fluid leak tester bottle. What sort of adaptors do you use to attach measuring devices to the cooling system?
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Re: Monitoring coolant pressure with a sensor

Postby STC » Sat Jan 14, 2017 10:16 pm

What sort of adaptors do you use to attach measuring devices to the cooling system?


Whatever fits between the adaptor and the fitting on your pressure transducer. All you need is an airtight seal between the two.
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Re: Monitoring coolant pressure with a sensor

Postby volrem » Wed Mar 22, 2017 9:36 pm

STC do you any captures to share?

I have tried this two times with no success to pinpoint cylinder.
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Re: Monitoring coolant pressure with a sensor

Postby STC » Wed Mar 22, 2017 11:26 pm

STC do you any captures to share?

Should have on my work laptop, will look tomorrow.

I have tried this two times with no success to pinpoint cylinder.

It wont work very well unless you know the secret.
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Re: Monitoring coolant pressure with a sensor

Postby RyanH » Sat Apr 01, 2017 8:22 am

Here is a capture of a 2004 Ford F-350 with a 6.0L Diesel with the common stretched head bolt issue these engine develop with a performance tune. Many of these will only show up when towing a heavy load for the customer. Coolant will vent from the degas bottle but most of the time they have no complaint.

In this capture you can see the pressure rise quickly to the degas bottle cap opening pressure of roughly 15 psi. I then vent the cooling system and continue to drive. Pressure once again builds to +15 psi.
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2004 F-350 6.0L Early Head Gasket Failure.psdata
(2.39 MiB) Downloaded 60 times
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Re: Monitoring coolant pressure with a sensor

Postby volrem » Sat Apr 01, 2017 9:12 pm

Nice capture but no clue what cylinder causes issue. I understand that this car has multiple cylinder issue but usually this is not the case.
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Re: Monitoring coolant pressure with a sensor

Postby RyanH » Sun Apr 02, 2017 7:33 am

Generally, these engine doesn't develop a misfire on one cylinder due to a head gasket issue. I was just posting one with an over pressurizing system. Now with an EGR cooler things get a bit tricky. Here is a post of one that is venting but the cause is an oil cooler restricting coolant flow to the EGR cooler, which in turn boils the coolant in the cooler and the resulting steam pressurizes the system.

This is interesting because of how quickly the pressure drops once the steam condenses. Also the fact that the steam pushes out air in this process. Once the steam contracts, the system can drop to a vacuum.
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2004 f-350 6.0L Early Plugged Oil Cooler Cooling System Boiling Coolant.psdata
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