1. Welcome to the new SAOCA website. Already a member? Simply click Log In/Sign Up up and to the right and use your same username and password from the old site. If you've forgotten your password, please send an email to membership@sunbeamalpine.org for assistance.

    If you're new here, click Log In/Sign Up and enter your information. We'll approve your account as quickly as possible.


    Dismiss Notice

Oil pressure relief valve info needed...

Discussion in '"Stock" Alpine' started by Alpineracer8, Feb 20, 2007.

  1. Alpineracer8

    Alpineracer8 Donation Time


    I have been researching what appears to be a rather lively discussion several years ago on the Forum regarding brass vs. steel oil pressure relief valves in spin-on oil filter bases on later Alpines. Not to restate all of this, but the problem is said to be either erratic pressure readings or low/non-existant pressure at idle. Prior to building the new 1600 engine for my racing Alpine Series I, I experienced the same "no oil pressure at idle" problem in my 1725 outlined in the earlier pressure relief valve discussion. The aforementioned 1725 had the spin-on oil filter base with the oil cooler block under the filter base that contained the inlet/outlet for the oil cooler lines along with the pressure relief valve. The previous owner had modified the pressure relief valve to be adjustable.

    Not knowing any better, I put this oil filter base/oil cooler & relief valve block set-up on my racing engine again. Now, from reading on the Forum, I find out that there has historically been a problem with the early style spin-on filter housings with the brass pressure relief valves; it seems the valves have a tendency to stick open, thereby allowing all the oil to bypass the motor and just get pumped back into the sump.

    My big question now is this...is there a way to tell which pressure relief valve I have? I realize that I can remove it and look at it, but I've seen some of these that have the relief valve on the front side of the cooler block. Mine happens to have the relief valve on the passenger side of the cooler block next to the cooler lines. If I do indeed need to take it apart, am I going to be looking for a brass piston AND sleeve, or just a brass piston? I've never had any experience with this sort of thing before so any help would be appreciated.

  2. jumpinjan

    jumpinjan Donation Time

    The valve on the right side of the engine is the pressure relief valve. The one forward, and on the cooling line block is a bypass valve.
    There are, what we have been calling a "sheet metal" style relief valve assembly. This looks like a rolled sheet metal tube and I think it has a brass valve. I think these are the ones that get stuck, although, I have not experienced one that was stuck. Do a search on the valve modification article that Tiger-Tom wrote. We don't have it here. Anyone remember that one?
  3. bkasl

    bkasl Silver Level Sponsor

    Tiger Tom sent that to me many years ago and I still have it if anybody needs a copy, in fact it is filed away in my Sunbeam Survivor notebook from SUNI 1, along with compilations of fix-it articles on just about any Sunbeam problem. Brent
  4. sunbeam74

    sunbeam74 Silver Level Sponsor

    Service bulletin

    Not sure if this is the information you are looking for but it identifies the pressure relief valve that has the problem. (not that they all don't have a bit of an issue but most of the others can be cleaned well enough to function normally)


    NUMBER: 66-6
    DATE: Sept. 26, 1966
    GROUP: Engine
    SUBGROUP: Oil Pressure Relive Valve

    MODELS: All Models Equipped With 1725cc Engine
    SUBJECT: Oil Pressure Relief Valve Change

    Some reports of early bearing failure and/or intermittent low oil pressure have been received. If this condition is encountered, it is recommended that the oil pressure relief valve part no. 5043949 be changed to the earlier type valve as fitted to the 1600 c.c. engine.

    The pressure relief valve 5043949 is no longer available and superseded to part number 5041317 which can be identified as follows:

    Valve part number 5043949 has a small plug on the center of the hexagon face.

    Valve part number 5041317 has a plain hexagon face.

    NOTE: Fitting of the early type valve will increase oil pressure from approximately 40 lbs. p.s.i. to 50 m.p.h. to 50-55 lbs. p.s.i. which is acceptable and should be explained to owners.

    T.H. Bullard
  5. Nickodell

    Nickodell Donation Time

    Andy: I had the stuck-valve problem three or four years ago - just suddenly saw the oil pressure sink to about 10 psi at running speed. At first I thought that I'd run a bearing, but as there were no expensive mechanical noises up front, and I was only 3 miles from home, I drove back carefully, keeping engine load to the minimum.

    Before disassembling the valve it was easy to see that the piston, or plunger, had stuck with the oil return port partially uncovered (hence I had at least some pressure). Inside I found a buildup of what looked like varnish on the inside of the valve body walls. I immersed the valve in lacquer thinner and exercized the piston by pushing it up and down, using my drill press with a flat-ended rod in the chuck.

    After ensuring that all the varnish was removed I then repeated the process with fresh engine oil, changing this twice to ensure that all the solvent had been removed, and refitted the valve, which has worked fine ever since.

    The other problem you can run into is a "step" worn into the cylinder wall by the constant movement of the piston (rather similar to an engine cylinder step, or ridge), which can also cause trouble. I imagine that the only solution in that case would be replacement of the valve.

    Personally, I'm against tinkering with the factory-set pressure by modifying the valve:

    Firstly, if you have low pressure it makes more sense to find out why (worn bearings?) and fix it before you have a catastrophic failure, rather than pumping up the pressure, which to me is like taking Tylenol for persistent headaches instead of investigating what is causing them.

    Secondly, oil flow is as important as pressure. Pushing up the pressure way over the designer's mark may make you feel good but it doesn't bring any real benefits. And it can even bring problems; someone on the old forum related how after he converted his relief valve and pushed the pressure up the first time he fired up the engine it blew the seal out of the oil filter and dumped the oil down his driveway. I would also be wary of the flexible lines to the oil cooler.

    That's just my opinion, of course. I could be wrong.
  6. Pumpkin

    Pumpkin Donation Time

    oil pressure

    Oh what a relief it was, after changing out an oil gauge... I had good pressure again. I had gone through the paines of making an adjustable relief valve ,,and it worked. But when I found another gauge that did it. :eek:

    I might suggest to simplily install on either off a "T" or straight on to a spare line to check it out. It might save a bunch of head aches..

Share This Page