Engine oil Thermostat.

[John L]

I have had one of these fitted with a cooler since I had this car, even after a good drive, I'm not sure if they are actually connected up correctly.  I know there should be an ideal temperature for the cooler to cut in, the Mocal one I see has a waxstat that opens at 80 degrees C.

On checking my stat it seems that its made by Flotec, it looks exactly the same as the Mocal one, but the parts inside are different, I had ordered a Mocal kit, but the parts inside are not the same.

Also I would like to confirm which pipes from the filter head adaptor go to the thermostat, would anybody have a few photos please? 

John

[John L]

Does anybody have any info please?

John

[John L]

Some pictures, the Mocal parts on the left, the flotec parts on the right.  The flotec has an o ring seal, and the waxstat is a bit different.

I ordered the Mocal parts kit as the unit looked just like it, but the writing on mine was at the back so didnt see it.

John 

[Brent C]

Hi John

I am surprised that you state that your Mocal thermostat opens at 80deg, as the way that the system works is that the thermostat is open below the desired oil temperature. The oil flows from the pump to the thermostat and takes the least line of resistance, which is across the thermostat and then onto the engine. When the oil temperature gets above the temperature that the thermostat is set to, the thermostat closes, forcing the oil to travel on and through the cooler. It is set up this way, so even if the thermostat fails closed, there is always a flow of oil to the engine.

Brent

[John L]

Hi Brent,

The 80 degrees should be when the valve diverts flow to the cooler, according to the Mocal site,  and yes the engine does get the first priority, but I'm trying find if it did actually open to the cooler,  my oil pressure when cold is good, 55-60 psi on my gauge, but once the engine has been run the pressure at idle when hot is down to just about a bar.  I have using some Penrite Classic 20/60 oil. 

Its had camshaft bushes fitted, no difference, new Witor oil pump, but still not that good at idle but was better when first fitted but has now crept down again at idle. 

So i was wondering if the cooler was actually doing anything,  the 2 pipes to the engine adaptor from the thermostat are hot, as is the bottom one to the cooler, but the top one from the cooler to the valve still remains pretty cool, so makes me think its not actually giving a good flow thru the cooler, ok so perhaps the cooler is partially blocked?  Unfortunately i dont have a good way of measuring the temperature.  Perhaps that should be the next step,  get an oil temp gauge.

John

[Tim D.]

Have a mocal setup. Engine pretty newly rebuilt and gey 25 psi+ at idle. Cool return from the Rad is what you want but as you say could also be low flow. Try using an infrared thermometer to measure before and after the stat opens. I can actually see mine open as a blip in the oil pressure on the guage. 

Tim

[astontr6]

40 minutes ago, Tim D. said:

Have a mocal setup. Engine pretty newly rebuilt and gey 25 psi+ at idle. Cool return from the Rad is what you want but as you say could also be low flow. Try using an infrared thermometer to measure before and after the stat opens. I can actually see mine open as a blip in the oil pressure on the guage. 

Tim

Hi John!

I have a Mocal set up with a Serck oil cooler. My oil pressure hot is 75 psi above 2000 RPM and 50 PSI at tick over hot. I do not have Spifire cam shaft bearings in mine, is still running on the cast iron block bearings as we could not detect wear when the engine was rebuilt, using tool room measuring equipment, But the camshaft was replaced by a Newman PH2 type. Were the tolerances of your new oil pump checked?? Get rid of most of the end float??Did you check the old cam shaft bearings for wear?

Bruce.

[John L]

A while ago I changed to a Newman cam, and the pressure was worse after that, I know their cams have bigger oil grooves, I bit the bullet and had cam bearings put in by Ivor Searle, and gave them the the cam to get it right.

The oil pump was meant to be a closer fit/checked one from Chris Witor.

I will see if I can borrow an infra red gadget and see what measurements I get.

I know the oil filter adaptor is I think a Mocal one, but it doesn't have the adjustable centre section, and I'm wondering now if the thick inner rubber ring is as good as it could  be.

Which is the pressure feed out of the filter adaptor, from the engine oil pump, is it the lower one?, I haven't checked loosening the fitting at the thermostat and removing the voltage from the coil,   and return from the thermostat to the oil filter adaptor at the top of the oil filter adaptor.

Water temp is good, and the block was acid dipped when it was at Ivor Searle's.

[Tim D.]

Also have cam bearings installed by Ivor.  

Tim

[astontr6]

19 hours ago, astontr6 said:

Hi John!

I have a Mocal set up with a Serck oil cooler. My oil pressure hot is 75 psi above 2000 RPM and 50 PSI at tick over hot. I do not have Spitfire cam shaft bearings in mine, is still running on the cast iron block bearings as we could not detect wear when the engine was rebuilt, using tool room measuring equipment, But the camshaft was replaced by a Newman PH2 type. Were the tolerances of your new oil pump checked?? Get rid of most of the end float?? Did you check the old cam shaft bearings for wear?

Bruce.

John,

Did you check the seat in the block for the oil pressure relief valve and the valve itself. These two parts are meant to be lapped in. These two parts have a tight tolerance on them and the repro ones are known to be often well out of tolerance.

Bruce.

[John L]

Still trying to trace this low pressure at idle, I wonder now if the takeoff adaptor for the filter I know is the old style, not like the new ones that have a way of pressing the inner large 0 ring onto the engine block, would this perhaps be the culprit?  The pressure has always been low at idle ever since I've had the car.

Has anybody ever come across the Flotec thermostat, I tried to get info form Mocal as it looks just the same item, but the internal parts are different inside and they didn't seem to have any info.

Does the engine oil relief valve seal on the taper at the end or on the diameter? I will need an endoscope to see inside. 

John

[super6al]

Hi John

Cant help with the thermostat & apologies if this sounds too obvious but is the oil pressure gauge reading correctly?

Alan

[Waldi]

Hi John,

The engine prv is a very basic plunjer and a spring. My new plunjer had a rather tight fit in the block bore, so I sanded it down a bit to avoid sticking in open (lifted) position.

Worth checking, it is not much work. Check spring length too.

Waldi

 

[Mike C]

3 hours ago, Waldi said:

Hi John,

The engine prv is a very basic plunjer and a spring. My new plunjer had a rather tight fit in the block bore, so I sanded it down a bit to avoid sticking in open (lifted) position.

Worth checking, it is not much work. Check spring length too.

Waldi

 

+1.Polished my plunger with cutting paste to ensure smooth operation without sticking.

[Kenrow]

Have you tried to put plugs in the filter adapter to bypass the oil cooler? If yes, any change in pressure?

[John L]

Ken,   Yes I joined the two pipes together, bypassing the cooler, but it's the same, that was why, could it be the oil take off adaptor, as I know it not the latest type with the adjustable middle section.  And also how does the relief valve work, does it seal on its end face or the diameter, uncovering a hole? even with the HD spring it still loses pressure at idle, down to between 1 and 2 bars.  I think the adaptor has to come off next.

John

[Kenrow]

I have a 25 year old NOS Mocal unit with oil cooler still in the box. Let me know if you need any measurements if it helps...

[Tim D.]

Hi John,

i just re read your thread. Is your major issue a loss of oil pressure?

did it happen suddenly or has it been gradual?

if it happened gradually, did you do anything before it changed?

I had a sudden change a while back and traced it to a gauge that was getting stuck for example.

why do you think it is the oil cooler? Did you alter something here?

i think if the pressure at idle is dropping it is probably not the cooler unless in the past it was cooling oil and hence increasing pressure and now for some reason it is bypassing and so the oil is heating more and pressure is dropping. To test this would be easy. Just check once fully warmed both pipes from the cooler are warm. One should be hotter than the other of course. 
 

tim

[Kenrow]

Just food for thought:

Oil Filter

[Rob Salisbury]

Hi John,

    Not mentioned so far but one very good reason for low hot idle pressure is worn crankshaft bearings,  ... how old are they and what make are they? ... during the years (nearly 25) I ran a Triumph 2.5Pi saloon I used to change the big ends at approximately 25000 intervals, the car had a thermostated oil cooler and a kenlow fan and would always have a hot idle of 25psi, only when that dropped below 20 psi I knew it was time to put in a new set of shells and luckily those were the days when genuine Vandervell VP2s were off the shelf from most outlets.  ..... may be worth dropping the sump and having a look?

Cheers Rob

[John L]

The std shells where changed for more std shells at the end of last year, when I had the cam bearings put in, and a new supposedly tight oil pump from Chis Witor, I did double check it, but still not that much better at idle oil pressure. I'm even using Penrite 20/60 classic oil. Currently using K&N long engine oil filter, but have used others in the past, with one hasn't dropped it anymore.  Perhaps might consider taking the cold oil pressure a bit higher to 80psi?  I never have had an external rocker feed pipe either.

I seemed now to have ruled out the oil cooler and thermostat valve now, so it must be the main relief valve, still need to find out how the valve seals, is it with the front face of the valve that has a chamfer or is it the outer diameter that does the sealing? even with the Moss HD spring it's still not that much better. What sort of tool will I need to recut the seat, something like a very small valve seat cutter perhaps, not easy to use paste, difficult to clean as engine is installed? 

John

[stuart]

This valve was removed from an engine that had more than 110psi oil pressure at cold (too strong a spring plus a washer) but it shows the shape of the valve face end.

Stuart.

 

[Waldi]

Hi John, the valve should seal on the front face. But given the tight fit in the bore in which it centers, that does “some secundary sealing” as well.

About lapping the block sealing face, I asked myself the same question, but only lapped it by some grinding paste.

The valve is very easy to remove, I would replace valve and spring but check the old valve for sticking first, as mentioned earlier.

Cheers,
Waldi

[Tim D.]

Probably a silly question.. But I didnt think that the main bypass valve doesn't influence idle oil pressure when hot, only when cold, preventing from going sky high with cold thick oil..

Tim

[Waldi]

Tim,

it should close when the pressure drops, as you say, but can stick in half-open position or not seal properly. The effect is more noticeable when hot & at idle.

Waldi