oil pressure on 1hz - what causes is to drop and what can be done to 'fix' it? (3 Viewers)

[sunrk]

I'm aware that a very old 1hz like the one in my 80 has a lot of wear and potentially blow-by.

I'm noticing when driving that the oil pressure is not coming much above 1/3 anymore and when idling (hot motor) the pressure goes to about 1/6 on the gauge.

I always change the filter with a genuine one and do oil changes roughly every 10000 km. I use Delo 400 multigrade oil. I always use an oil system flush (Nulon is the one I use) as part of the oil change routine.

I've not replaced the oil pressure sender or any other parts of the oil system besides replacing the filter when I do oil changes.

I've tried stuff like 'worn engine treatment' etc. in the oil and really those products do nothing that I can determine apart from perhaps a very short term improvement in oil flow by improving the wear properties.

Putting aside the fact that the motor is very old and worn, is servicing the oil pump, etc. a feasible thing to consider and is it something that's relatively easy to do with the motor in the vehicle?

 

[mudgudgeon]

Most likely problem is just general wear on bearing surfaces leading to out of spec clearances on things like crank main and big end bearings and crank journals surfaces, and camshaft bearings and cam journal surfaces.

As bearings wear, clearances increase, your oil pump is pumping the same amount of oil into a bigger gap. This equals a reduction in pressure. Oil also escapes out of these areas faster, so again a reduction in pressure.
The pump itself will also wear, clearances on the impeller and thrust surfaces will increase, reducing effectiveness of the pump.

Solutions?
- Replace worn bearings. If crank journals are worn, this will limit how effective this is.
- Rebuild the oil pump. Same as above

 

[sodafeld1]

Not too familiar with hz and it's longevity, (think they can get a million k's) but on the 2h, it can be increased with the pressure relief valve by packing the spring with washers. Not that this is advisable.

The 2h can blow oil filters with too much oil pressure if the relief valve gets stuck. I mucked around a fair bit with oil pressure with electric, mechanical gauges and the relief valve, relief spring length and tension, and different oil viscosity. Thicker oil does a little bit, but not much. Old oil gets tired too. Warm weather and long drives makes the oil a bit thinner too, not by much.

If any comfort, a digital oil pressure gauge can let you know exactly what psi you have if you measure it against a mechanical gauge. I find that the ome gauge is not very accurate. The ome gauge can read 1/3 but be 70 psi on the digital, which is plenty. Over 100psi you may pop the filter.

As long as psi is in fsm spec, you got be happy with that. For the 2h , fsm says as low as something like 7psi at idle is ok, but I would be worried to be that low.
How many k's you got? If it is just worn, that is life.

 

[sunrk]

Thx it definitely is happening only with the engine warmed up. When the motor first starts the oil pressure shows a good measure on the gauge and as it warms up the pressure readings go right down. I checked the oil level today since I'm in the engine bay doing the fender panel job and it's good, but I'll check again when running just to be sure.

 

[suzuguru]

Thx it definitely is happening only with the engine warmed up. When the motor first starts the oil pressure shows a good measure on the gauge and as it warms up the pressure readings go right down. I checked the oil level today since I'm in the engine bay doing the fender panel job and it's good, but I'll check again when running just to be sure.

It shows good pressure initially because the oil is thick from lack of heat. Once the temp of the oil starts to rise, the viscosity will go down. Therefore, the pressure goes down. That, as stated above, can be due to several things. I would say that it is most commonly associated with a worn oil pump.

 

[mudgudgeon]

Good call on checking with a gauge and not just relying on the OEM dash gauge.

Without a secondary gauge and relying on the factory gauge, there's no way to know how much of a drop is actually occurring

 

[sunrk]

Soooo. what is the best way to set up to have a secondary, proper oil pressure gauge even if it's not a permanent thing fitted in the dash but one that can be connected when required for testing? Is there a need to monitor both oil pressure and temp or can it be presumed that oil temp and coolant temp are basically matched?

 

[sodafeld1]

search on here, or google, i did it along with a 'bypass oil filter rave'. I feel naked now without my extra oil and temp gauge.
mind you, always a little something on old cars..

 

[sodafeld1]

oh

search on here, or google, i did it along with a 'bypass oil filter rave'. I feel naked now without my extra oil and temp gauge.
mind you, always a little something on old cars..

oh, 690k's! well no wonder, there is a guy here who got a million k's on his 12ht with the same oil pump. Whilst you probably alright for a bit, personally I would be slowly be gathering parts for a rebuild for the future. Parts go up in price, not as quick as vegies, but noticable.
I am slowly building a second 2h.

The extra gauges just give you some reassurance.

 

[sodafeld1]

temp I use aussie engine guard, it's a ripper.

 

[sunrk]

I have a Watchdog TM2 for coolant temp (sensor mounted to top of motor near radiator hose connection), but need to figure out what do to if I want a permanent oil pressure monitor or not.

 

[sodafeld1]

reality is we don't need much, most oil gauges are a simple red light when there is no oil

 

[ngaritj]

This may trigger a new debate but, I change oil every 5000Ks, as recommended by the manufacturer. Everybody tells me the recommendation for today is 10,000 but, call me cynical, I believe the rationale is, wear out your motor faster and be forced to buy a new one.

 

[sodafeld1]

This may trigger a new debate but, I change oil every 5000Ks, as recommended by the manufacturer. Everybody tells me the recommendation for today is 10,000 but, call me cynical, I believe the rationale is, wear out your motor faster and be forced to buy a new one.

with ya there brother! clean oil is the best

 

[sunrk]

What are the actual oil pressure specs for a 1hz motor? I'm aware the Toyota factory gauge in diesel vehicle with an oil pressure gauge is uncalibrated.

 

[sodafeld1]

What are the actual oil pressure specs for a 1hz motor? I'm aware the Toyota factory gauge in diesel vehicle with an oil pressure gauge is uncalibrated.

get an fsm

 

[PEOPLES]

What are the actual oil pressure specs for a 1hz motor?

I'm not familiar with the 1hz but a rule of thump is: rpm / 1000 in bar oil pressure

Idle at 600min-1 -> 0.6bar oil pressure (maybe 7.5PSI)
1500min-1 -> 1.5bar or 22PSI
3000min-1 -> 3 bar or 45PSI

often the limits by the manufacturer are a little bit lower, so the upper values are on the "good" side. In real life, a healthy engine has more then this.
The background is, that there is a minimum pressure needed to push the oil into and through the crankshaft against the centrifugal force, to get to the lubrication points of the connecting rods.

I've not replaced the oil pressure sender or any other parts of the oil system

Usually the oil pump is not the problem. Worn bearings can be.
If there is a drop in oilpressure under higher rpm, then maybe the inlet filter/screen of the oil pump is clogged. If there is a drop in oil pressure at same rpm but different load, it can be a sign for worn bearings.

I had a broken oil pressure sender at my J4, replaced it and everything was fine, but over a time of around 4-5 months the oil pressure trent dropped. I did a oil change but no change in behaviour. I removed the sender and tested with a air pump of my bicycle (with gage) and: The sender gave only half the pressure, BUT constantly over the whole range. Very tricky, because the behaviour of the oil pressure seemed reasonable, but too low.
A new sender fixed the fault.

BUT, as long as you not have verified the sender to be faulty, consider you have a real oil pressure "problem".

 

[MUDZLLA]

I've had 3 1HD-T's and talked with a few others that had this motor - no-one sees much pressure in these engines. It's usually just above the low pressure mark when at operating temp. Mileage on all was around 170-220k km.

If ppl have other experience I'd like to know.

 

[John Young]

I have just acquired a Middle East diesel 105 with 450k km on the clock. Drove it for the first time last evening. Oil pressure struggles to reach 1/4 but most of the time just hovers over the last line, as in close to zero. This was a government truck so I do know know how good the maintenance was on it. This may be an ignorant question but does anyone think this might be a sender / sensor issue? The pressure reading is also a little strange in that when I am braking or accelerating strongly the oil pressure seems to go up, which would suggest perhaps some kind of sloshing related event. But I'm really puzzled at this point.

For the moment I am driving the truck in as gentle a manner as possible, watching temp and oil pressure such as it is.

I've also been offered a fresh, Japanese fire truck motor with 14k km on the clock for probably about 6K USD. Noodling the idea of just swapping in a near-new firetruck engine. Any thoughts on that?

 

[sodafeld1]

I do not know much about the hz but installed two after market oil pressure gauges + sender , one mechanical and one electric on my 2h. Worthwhile in my opinion, on the 2h gauges are not very accurate. The autometer and marshal gauges are much more real time responsive.
Did an aftermarket temp gauge too, I watch the numbers so I can turn the tunes up, carefree.

The 2h has 2 oil pressure relief valves with springs, the one on the block can be fiddled with, I trimmed my new spring one coil and packed with a thin washer. This can alter your oil pressure to adjustment of personal 'taste'..

Accelerating affects oil pressure, but braking shouldn't as much besides lowering revs creating lower pressure. It is directly related to your revs. If it does the same thing on accelerating and braking then it maybe an electrical gremlin, like a corroded earth.

After much research and observation I have concluded on the 2h that around 70-80psi(which is within factory spec) is optimal oil pressure for around 2000-2100 rpm. This is the minimum oil pressure required to spin centrifuge oil spinners (another aftermarket thing but use to come standard on the older 2h).

Type of oil and oil level makes a difference too. I believe you require mineral oil, synthetic oils would generally be too thin for your engine. Ambient temp does a little too.

Someone fluent in hz should chime in. Get a factory manual, a toyota one.

I am not overly comforted with the low oil pressure numbers that the 2h factory manual allow, I think around 7psi is ok at idle from memory. But I idle at lowest 30psi which is close to the lowest line on the factory needle. Better a bit high with lots of luscious clean oil lubricating everywhere in your engine. But not too high or you pop your oil filter, say over 100psi. Over filling the oil can cause this too, which can even bend or crack crank shafts.

But I wanted to keep my engine so worth the time and money.

The hz can get a million kms, which is something to be really proud of.

What oil do you have in there?