1975 230 manual oil pressure relief valve?

[samuiholidayhomes]

Oil leaking steadily and slowly, with no obvious source. Oil pressure climbs off the scale within a couple of seconds of ignition. Guessing the oil pressure relief valve could be stuck/blown/gummed/vulcanised...Any ideas on where this is located, and how I can service it? Mechanics on Koh Samui are smiley, honest, and totally unable to handle anthying beyond a hammer, wrench, and oxy-acetylene torch...

The diaphragm on my power brake booster also seems to be shot, as are most of the 30 year old rubber components; hissing air loss from the manifold, as massive suction causes the engine to shake and judder while brakes are applied. I'm thinking of disconnecting the air hose from the manifold until I can salvage a replacement booster. Any thoughts???

Any help would be greatly appreciated!!!

 

[guydewdney]

no - this is normal. the oil pressure should go to the top (over 3) after 1 second of running....

as for the brakes - there should be a one way valve - check this?

 

[dieseldes]

It's a fairly common problem, Its most probably the sender which is at the n/s rear of the engine block by the filter, unlike the diesels of that age the oil pressure sender is electrical, I have had 2 fail on me, one went full scale deflection as soon as you switched the ignition on and one where it would go full scale and as you were driving along suddenly dropped to 1 bar or less!! that caused a few heart stopping moments!!.
Replacement cured it, in both cases a visit to the local breakers found a working one.
IIRC both the faulty ones rattled when you shook them

Des

 

[guydewdney]

oil pressure sender on a 1975 W115 is mechanical - its a pipe from the oil pump to the dashboard...

Well - it is on my 1972 w114 280CE, and my old 1972 W114 250... and it is on the W116 540SEL 6.9 that I have just taken apart....

Oil level is dropping - is there any smoke? Pull off the pipe to the air intake / filter - is there a lot of smoke / oil mist (this shows a worn engine, and is pumping the oil / air into the intake)?

Ill try to get a chance to look up the pressure relief valve on a 230 when I get home

 

[dieseldes]

I have my years confused I assumed it was a 123 petrol 230, which didn't come out till 1976

Des

 

[samuiholidayhomes]

Thanks for your help Guy and Des! I've been trying US forums for a few weeks, and this UK group is a lot more attentive and giving! The 230 straight 4 petrol was manufactured from 74-76, according to my research. Exhaust is clean, with no smoke. The oil pressure guage shoots straight up to max within a couple of seconds of ignition, and remains constant at 45lb/in2? on my scale, until the engine is shut off. Perhaps this is normal; I was just hoping that a stuck relief valve would be easier to remedy than a leak in the oil pan/gasket...

There is a 1-way valve on the air pipe between the manifold intake and the brake booster, although this is 1-way towards the booster, which is the problem. Any tip on how to disconnect the plastic pipes without breaking them? I'd like to repair/service the booster if possible, but the Yanks and Thais say "no can do"; found a guide for diassembling an old Chevvy booster, but can probably do without power brakes; just want to get rid of the hiss and judder.

Any further enlightenment greatly appreciated!

 

[guydewdney]

i have found the oil prssure relief valve - its on the bottom of the oil pump, which is under the distributor. its a small (?17mm? 15mm? spanner) bolt going upwards.

the brake booster (the large drum with the diaphram in it that you think is leaking) is part number 001 430 66 30 - this is the same part as in on EVERY W114 W115 and W123 car. Try to find one of these in the scrapyard and replace it.

in my opinion, you need power brakes.

the pipe should unbolt from the booster - not slip off. the same applies for the engine end

 

[guydewdney]

ah- forgotten somthing.

theres an O ring between the master cylinder and the servo drum - maybe this has 'gone' - this would cause the hissing you talk of.

 

[samuiholidayhomes]

Thanks for your help and advice Guy! Something has definitely gone in the booster system, and I hope to find a salvage yard within the next couple of weeks, although it's a major expedition from here to get to one. Many of the rubber components seem to have perished in the tropical heat... The pipes that connect the booster to the manifold are translucent plastic, in 2 sections, with a 1-way valve between them. All joints are push-on, to male segmented parts for grip, but seem to be well sealed and rigid, either due to a solvent welding, or possibly just heat and time. The pipe seems quite hard, and I'm concerned that it will crack if too much pressure is applied; possibly some heat would work? Is the o-ring something I might be able to find

I'll have a go at the pressure relief valve, and hope that it can be tweaked into shape. At present, oil pressure seems to be way too high, although this could be due a problem with the guage on the dash....In any case, oil is seeping all too rapidly. I found a suspicious looking bolt on the oil pan, which isn't fully tightened, but seems to be stuck, although I still suspect that excessive oil pressure is causing most of the leakage...

 

[guydewdney]

the O ring is between the master cylinder (the cast aluminium part, with the brake pipes in it, and the fluid reservoir on top) and the vacuum drum part.

the vacuum hose is very hard on mine as well - i wouldnt try to disconnect it.

I dont think the relief valve is wrong - change the oil and the filter, and leave it alone.

 

[samuiholidayhomes]

O ring master brake cylinder

Thanks again Guy! I'll certainly try to check out the o-ring connection. Briefly checked the brake system today, and topped up the fluid. On the brake fluid reservoir, I have 3 caps of about 2" diameter; a central one for filling, and one on either side, which have copper electrical wiring connecting them. The wire is broken; do you have any idea of their purpose, of if the break could be a relevant factor?

 

[samuiholidayhomes]

Wiring on brake fluid reservoir

I suspect that the broken wire could be for the brake lights; does that make sense? Looks like the wire may have been cut, possibly as a poor fix to a short circuit, or defunct sensors if they are indeed present. Yet another replacement part to search for in the breakers yard...