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MG TD TF 1500 - Oil Pressure Oddities from Lazarus

Just thought I'd share some thoughts from an email that I sent to MGBob:
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Amazing the number of things that these machines can fool us with. For quite a few years I've (now past tense I'd) been bragging about my 85-90 psi oil pressure at cruising speeds. About a month ago I decided to reinstall the single oil pressure gauge that was OEM for Lazarus, replaced by a combo gauge, just to see what it would show me. For a number of reasons I could only do an in-the-driveway check. As expected, the reading went right up to 50 psi at idle. Goosed the throttle and watched the needle climb up into 65 psi'ish range and show no sign of going any higher. Hmmm? Borrowed a test oil pressure gauge from my local garage and was able to plug it into the end of the oil pressure hose that leads to the coupling on the firewall. Fired up the engine and saw similar readings. Seems as if my to-be-envious-about oil pressure readings are the result of a very non-linear over 60 psi gauge. Looks as if the oil pressure relief valve is set at about 65 psi. Now if only I knew how to calibrate a bourdon tube oil pressure gauge.

Next chapter in that story is even better. I've virtually solved my oil drip problems. Messing with the oil pressure hose gave me some very oily, messy hands. Made me wonder. When I started thinking about it I remembered that the OEM-style, fabric-covered hose with the wire wrapped around it, came with the engine about 25 years ago. The cost of a new OEM-style hose vs. a modern flexible one is something like $60 vs. $18. Bought the modern one. All of a sudden my consumption of kitty litter for the garage floor has virtually ended. Seepage from the hose was the major cause of my leakage.
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Amazing machines, arent't they? Bud
Bud Krueger

Interesting---Bud, Where did you buy your new modern hose and did it fit the British threads without changes? Can you give us a part Number?
Richard Cameron

My wallet found it at Moss (thru LBCarCo). Moss #376-060. Yes, it threaded right on. Bud
Bud Krueger

Bud,

It sounds like you have ideal oil pressure now. I think 60 is plenty high enough. I know it is not very common but the oil pump drive gear / cam gear can fail on XPAGS so they don't need any extra stress. I once had these gears strip in my TC race car due to excess oil pressure. It ruined a new (old stock) factory "full race" cam! :(

Bob Schapel
R L Schapel

I certainly agree with you, Bob. I can thank Lawrie Alexander, the late Skip Kelsey and Carl Cederstrand for helping me to put it together. And, that was about 20,000 miles ago. Bud
Bud Krueger

Bud

Find an instrument repair shop with a "Dead Weight Tester" and they will quickly recal your gauge in the reading range that is critical. Linearity will be an issue if the Bourdon Tube has been stressed.

Graeme
G Evans

Thanks, Graeme, but it's fine in the important (<60) range. And, the 80-90 readings are impressive. Bud
Bud Krueger

After my engine rebuild over this past winter, my oil pressure cold is 80#. After warm up, 65#, hot 50#. No rude noises.
R C Flowers

This thread was discussed between 02/09/2014 and 03/09/2014

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