Oil Pressure Switches

[Banjo]

I've recently had two oil pressure switches fail in as many weeks. I both cases oils was seeping out of the oil pressure switch between the electical spade terminal & the plastic/bakelite material that surrounds it.

 

I took it out, looked around the garage, & replaced it with another identical one. A week or so after it did the same thing, leaking oil out of the same point.

 

I don't know whether the two pressure switches I used were original Toyota fitted switches or aftermaket ones, which were added to engines I have over time. When the second one failed, I dug up another one off a 3K motor that had a button type electrical connector, rather than the spade terminal. It's been in for some time now, and the problem has been cured.

 

The electrical wire in the harness that connects to the oil pressure switch is designed with a slot in it so it can be fitted to either type of oil pressure switch electrical connector, so I'm not sure whether Toyota used both types at times or what.

 

I'd be interested to know whether others have ever had suffered an oil leak in this area.

 

The oil pressure switches have a tapered thread on them, and you have to be very careful tightening them up, as too tight, will actually crack the aluminium housing into which it is screwed. Believe me, I did it ! Anyway, off with the housing & filter, and scout around the garage for another one. I found two, but they were different. They both fitted OK, but one had a pressure relief valve built in & the other had none.

 

If the pressure relief valve is not in the filter housing then it must be in the oil pump in the sump. So presumably there must be some KE oil pumps with builtin pressure relief valves, and some without.

 

That raised the question, what happens if a motor gets fitted during it's life with a oil filter mounting plate without a pressure relief vale, and an oil pump also without a pressure relief valve.

 

I wasn't going to pull off the sump to have a look, so I I fitted a replacement oil filter housing with a pressure relief valve, because the one I cracked did not have a pressure relief valve fitted. I figured if the engine already had an oil pump with an oil pressure relief valve fitted, it couldn't do any harm to have two in series.

Certainly better than having none at all.

 

So what if my 4K motor of unknown origins, does not have an oil pump with a pressure relief valve fitted. As the weather is now just starting to cool off, maybe the pressure was higher first thing in the morning, with no relief valve, so it blew the oil pressure switch. The oil filter was new, so there was no more than normal resistance there. It seems a it hard to believe that oil pressure could build up so high to blow a pressure switch, as a older worn motor has a lot more clearance than a new one.

 

Anyone experienced this before or has any ideas.

 

Cheers

 

Banjo :dance:

[Browland]

The valve in the filter body is an oil filter bypass valve. If the filter becomes blocked the valve will open and oil will still flow to the oil gallerys. Works on pressure differential between the "dirty" oil and "clean" oil sides of the filter. The spring normaly keeps the valve shut but if the oil pressure before the filter is greater than the pressure in the oil gallerys after the filter (caused by blocked oil filter) the valve will open and let oil flow to the oil gallerys. Unfiltered oil is better than no oil.

[Banjo]

The valve in the filter body is an oil filter bypass valve. If the filter becomes blocked the valve will open and oil will still flow to the oil gallerys. Works on pressure differential between the "dirty" oil and "clean" oil sides of the filter. The spring normaly keeps the valve shut but if the oil pressure before the filter is greater than the pressure in the oil gallerys after the filter (caused by blocked oil filter) the valve will open and let oil flow to the oil gallerys. Unfiltered oil is better than no oil.

 

Thanks Browland

 

I remembered after I posted the above, I had a complete factory manual on the 3K 4K & 5K series engine. I looked up the lubrication section, (which is pretty short on detail) but it does show that all oil pumps in all K engines had a pressure relief vale incorporated. If that is the case, then the valve in the filter body I have, has to be a filter bypass valve as you rightly describe. However, what it does mean, is that some K series motors were fitted with an oil filter bypass valve & others not. The factory manual doesn't give the filter bypass valve a mention at all.

 

Thanks again for your input.

 

Cheers

 

Banjo :dance: