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MG Midget and Sprite Technical - 1275... Oil leak & other problems

Hi all, I'm workign on chasing down a couple of problems I have had with my engine and thought I might see if you lot have some diagnosis that I haven't come up with.

As some may Know i have recently put in a Datsun 5 speed (rivergate kit) and it is awesome. in the time since the engine went back in (about 500 miles or so) I have had a few little problems. I sorted a few myself, tuning revealed the timing was over advanced, it is now timed correctly. anyway, here are the ones that are bothering me.

1. i have an oil leak from the front of the engine. It is hard to see where it is coming from, but it looks like the timing chaing cover is clean, so it is not the crank seal ( i think) which makes me think it either the timing chain cover gasket, OR the sump gasket has worn out. (the sump gasket was not changed when the engine was out, but the timing chain gasket was). I know this is the source of the leak, because there will be oil sitting on the front cross member. This leak only happens when the engine is running, not right away but after the car has been driven for a while i will see fluctuation in the oil pressure, it will drop from around 40-50 to about 20. when i stop i will have to put in a quart or more. The oil leak itself isn't too troubling, since i jsut have to identify the source and re-seal. I will also check that the timing cover breather isn't clogged (thus limiting the effect of vacuum).

2. the other wierd thing it is doing is after the engine has been run fast for quite a while, it will start trying to stall when you slow down. Like exiting a highway and dropping from 70mph to slow down for a stop light, the idle (which is normally very steady at ~1000rpm) will drop to 500 or even try to stall. I can stop it from stalling by goosing the accellerator or pulling the choke to richen the mixture. again, it only does this when it has been run for a while.

any comments would be welcome. I don't think these two problems are related, but i'm not sure which I should be addressing first or even how to proceed for diagnostics, etc.

thanks,
Chris
Chris Edwards

if you ever set the engine on the ground, then I would suspect the oil pan (the weight of the engine will crush the gasket and wreck it)

when you re-installed the timing cover, did you center the seal on the shaft before you torqued it down? Not doing this will case the seal to leak.

the change in oil pressure is weird. An oil leak that is big enough to cause a pressure change sounds fatal.


regarding the stalling, can you tell us: what engine, what carburetors, what year is your car (emissions)?


Norm
Norm Kerr

1973, 1275, HS2 (new 5 years ago) carbs.
Chris Edwards

hmmmm,

Check the jet tubes for gunk. the tube that goes from the float bowls to the jet, they can get clogged! also make sure the carb pistons can move freely both UP and DOWN, look for wear on the needles and jets

>>>>>>after the car has been driven for a while i will see fluctuation in the oil pressure, it will drop from around 40-50 to about 20.<<<<<<<<

do you mean it moves up and down as you drive, or does it drop to 20 psi when you come to a stop or low idle

If its the former...
Oouuuuu... thats not good! that what my engine was doing right before the crankshaft broke

if its the later...thats fine no issue
Prop

fluctuating isn't exactly what I mean, it doesn't swing up and down or anything. It drops when i slow down of course, but when it troubles me is the oil pressure at speed will gradually fall. It will recover sometimes, going back up a little bit. I haven't identified consistently what causes it to partially recover pressure, could be just that the engien gets cooled down a bit and pressure improves. I also haven't tested my oil pressure gauge. It could be temperature related, if the oil thins as it gets warmed up? I haven't got an oil cooler fitted yet. I have a new oil cooler but haven't bought the hoses yet. I don't want to introduce a potential leak until i have solved the current ones (or at least identified them). I use 20/50 oil.

i suspect the sump gasket, as the engine did rest on the ground while it was being worked on, and this added stress combined with an old gasket could cause a failure. also, as I mentioned the front of the timing cover is clean (no evidence of oil running down it) as far as I can see.
Chris Edwards

I have read that the oilsump can be removed without pulling the engine, so that is my plan to change the oil sump gaskets and seals. That is plan A.

I may be dealing with separate problems (1. a leak, and 2. lower oil pressure from oil getting too hot) or they may be related, i don't know. possibly i need to look at the oil pressure relief spring too... one problem at a time however.

is there anything special I need to know about removing the oil sump from below? I assume once I get underneath the car it will just be a matter of bracing something under the pan until I get the bolts undone and then it will drop straight down?
Chris Edwards


"is there anything special I need to know about removing the oil sump from below?"

Yep drain before you start lol :-)
K Harris

Chances are it won't "drop straight down" because there will be enough stickiness in the gasket seal to support the empty sump. Likely to need a bit of a tap to get it to come free. So bracing something under the pan is probably unnecessary and will just get in the way.

Even when drained, it WILL drip oil, and MOWOG law says the drips will go straight into your eye so wear eye protection!

When the sump is removed and the old gasket material all cleaned off, check the surface of the pressed steel flange with a straight edge. They almost always get distorted with little raised areas around each bolt hole and these should be dressed flat again with light taps with a hammer to ensure a good fit with the new gasket.

Guy
Guy Weller

Chris,

If you have the 1275 You cant replace the oil pump with the engine installed. the oil pump is installed on the back side of the camshaft under the oil pump cover...If it does ultimatle prove to be an oil pump going bad...check back with the BBS as I think you can install a extreior dry sump oil pump...But I know nothing about that kind of thing ...probably get one thur summit racing or jegs

the oil leak and the oil pressure are 2 differant systems...oil pressure is sucked up thur a pipe in the sump pan into the pump behind the camshaft and forced thur the crankshaft and other passageways in the block

another thought would be to pull the oil pressure valve for a good cleaning and inspection it could be sticking...its a hollow nut with a spring and a bullet shaped shell that spring goes into its the big nut next to the dissy about 1.5 inches in diameter, and has the little cap on the top of the cap

another thought if you replaced alot of gaskets and used silicone when you did the 5 speed conversion...I wonder if you could have gotten silicon into the oil system...wouldnt take much

definatly check the gauge...agianst a known good one

Make sure the oil line from the block to the oil filter housing isnt blocked, kinked or twisted

make sure the oil is just regular oil not full senthetic I can see that being an issue but never heard of it being

loosen all the oil pan screws first, then remove them most likely the pan will be well stuck on so you will need several size scrapers and razor kniefs...to break the seal Dont use anything that can bend the lip of the pan. get some PB breaker also and keep an easy out close by incase the 40 year old steel screw heads twist off...(yeah Ive never seen that happen before LOL)

when you install the pan, get all the screws started and do a few turns at a time in a zig zag fashion to avoid warping the pan as it likes to twist around

DO NOT OVER TIGHTEN the screws on the pan...vary common, it will warp the edge of the pan ... just good and snug...I always clean the screws and holes really well and add a dab of high temp/oil resistant silicone to the threads when installing keeps them from loosning do to vibration...If you got an extra few dollars replace the screws with stainless steel so they wont corroid in the screw holes...makes like easier next time

Prop

Prop

A good tip for keeping sump gaskets in place, is to get about four bolts the same size and thread, and cut the heads off. Then you can use these to hold the gasket aligned, and fit the sump over the headless bolts. Fit the remaining normal bolts, then remove the headless bolts, and fit the standard.

Dave
Dave Barrow

Good tips, Dave and Prop! Thanks. As soon as parts arrive, I'll whip that sump off and sort it out.

Cheers,
Chris
Chris Edwards

This thread was discussed between 30/07/2010 and 02/08/2010

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