Monitoring coolant pressure with a sensor

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Re: Monitoring coolant pressure with a sensor

Postby Steve Smith » Mon Apr 24, 2017 3:53 pm

Hello and thank you for the posts. Some interesting research here and one I have experimented with using the infamous Toyota AD Diesel engines. (Given head gasket failure is common)

Like you Volrem I wanted to know if it was possible to locate the offending cylinder looking at coolant pressure pulsations using an engine with a known head gasket failure. I have to agree it looks to be challenging.

The AD engine head gasket fails between the head gasket flame ring and coolant jacket at cylinder 2 or 3. Here is a typical example:

HEAD GASKET FAILURE- CYL HEAD FACE .jpg
HEADGASKET FAILURE WITNESS MARK


The waveform below was taken from an AD engine with a clear head gasket failure. During cranking you can see how the pressure rises dramatically and then progressively falls whilst pressure pulsations in relation to cylinder 1 are reasonably uniform for a short period of time.

COOLANT PRESSURE AT START UP.jpg
HEADGASKET FAILURE


UNIFORM COOLANT PULSATIONS.jpg
UNIFORM COOLANT PULSATIONS


What I like about the test is that we can present customers with evidence of a diagnostic procedure being carried out and undeniable proof a major repair is now required.

Here is another example of an AD engine head gasket failure under full boost driving conditions only. Note how the coolant pressure increases in proportion to boost/manifold pressure.

HEAD GASKET FAILURE ONLY UNDER BOOST CONDITIONS.jpg
HEADGASKET FAILURE UNDER BOOST CONDITIONS


This engine would drive fine without coolant pressure issues if driven conservatively but as soon as full torque was required the coolant pressure cap would vent to atmosphere (accompanied with loss of coolant)

Moving away from head gasket failure, we can use the pressure transducer to qualify the water pump impeller operation.

Attaching the WPS to the expansion bottle cap whilst free revving the engine will record pressure changes inside the expansion bottle we can attribute to water pump activity.

WPS FITMENT.jpg
WPS FITMENT


WATER PUMP IMPELLOR TEST.jpg
WATER PUMP IMPELLER TEST


Above we have the activity recorded inside the coolant expansion bottle via WPS using channel D.
Simultaneously we can graph the theoretical water pump speed using a math channel to calculate engine speed multiplied by the ratio between the crankshaft and water pump pulley.
This is ideal for those water pumps whose impeller can become detached from the water pump drive shaft.

Moving on slightly, such a test is ideal to qualify Hybrid/EV water pump operation using a scan tool to “Active Test” or “Drive” the coolant pump

Once again this provides documented evidence of diagnosis and undeniable test results.

I would like to see a coolant pressure capture where using a sync to cylinder 1 has conclusively revealed the offending cylinder.

Take care. Steve
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Re: Monitoring coolant pressure with a sensor

Postby STC » Mon Apr 24, 2017 10:17 pm

Hi Steve

Offending cylinder Id is better achieved with the coolant jacket drained, empty. As you have found, with coolant present, circulation, pump activity etc. it does make the result a bit fluffy.

Not sure how it will fare with such a slight escape that occurs only under full boost. Would you want to load it to achieve those conditions without coolant ?
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Re: Monitoring coolant pressure with a sensor

Postby Steve Smith » Tue Apr 25, 2017 3:15 pm

Thanks for the feedback STC and nice touch too "Coolant Jacket Drained" I missed that.

I guess if we have enough evidence to confirm an over-pressure condition within the cooling system, the next step would be to request authority from the customer to drain coolant in an attempt to identify the offending cylinder as in the case of the Avensis above

It may take longer, but the more evidence we gather before stripping the engine the better.

Take care.......Steve
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Re: Monitoring coolant pressure with a sensor

Postby STC » Tue Apr 25, 2017 11:18 pm

Hi (again) Steve

the next step would be to request authority from the customer to drain coolant in an attempt to identify the offending cylinder


With the Avensis there would be no real value to the customer in draining the coolant and confirming the offending cylinder. Your customer is either Replacing the H Gasket, Selling or Scrapping it !
You would want to be doing that for your own personal satisfaction, and not in chargeable time.

However, if this was a "V" Configuration Engine then there is justification in confirming the offending bank and then there is a choice of fitting one or both gaskets.

Possibly bad practice to fit only one however something tells me that some VM's would subscribe to that test and outcome for warranty repairs.
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