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MG Midget and Sprite Technical - -Tsjirping- sound at 40mph

It was quite a warm day and at some point I heard a weird "tsjirping" sound coming from under the hood driving at about 40mph.

The sound was not reacting on the gaspedal, I mean: more gas or less gas did not affect the sound but when the car slowed down to 35 mph the sound stopped again.

We drove about 50 km and then stopped for several hours, when we drove of again first everything was OK, but after 10 or 15M the sound started again, it sounds a bit like the V-belt slipping or a metal to metal sound, not really disturbing but I do not like it....

the sound only appears on 40mph or higher
An other thing which also happend that day was the oil pressure after a hour drive went down to about 10-15 psi (at 900RPM), the oil was changed two weeks ago (20W50) and there is enough oil inside when I checked it.

would the oil pressure and the sound have to something to do with eachother or would it be something with the fan starting to freewheel?

What is the best way to check both problems and what are solutions......?
T.A. VanderVeen

what model and year is your midget, is it a 1500?
David Smith

TA - 10-15 psi at 900 rpm is a bit on the low side, but not unreasonably so. Rule of thumb is that you should have 10 psi for every 1000 rpm.

Your "tsjirping" (I assume that this is a Dutch word) could be any number of things, a water pump or dynamo pulley that are loose, a water pump or dynamo bearing that is running dry or a dynamo with a excessively worn rear bushing, to the point that the armature is beginning to rub on the field poles. If you have been running with a tight fan belt, and of the above, but especially the last item could be the problem. Always keep the fan belt loose on a car with a dynamo. See the article, Keep Your Belts Loose under Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

im guessing the "tsjirping"...is your throttle bearing oil is a bit low....

Prop

sorry....just kidding on the above.....does it do it at ideal....can you find the genral area where the sound is emmitnating from...try a long screw driver put the handle to your forehead, closed eyeball, or ear, or front teeth,,,and the sharp part of screw driver on the metal, where the sound ????? is comming from to hear it better....


prop
Prop

First off all: Thanks for the reactions!!

Sorry, I forgot to mention: the car is a MG Midget 1500, 1976 (check my website in Dutch: http://www.midget.tk)

"Tsjirping" is probably a Dutch word, but if you say it out load just the way its written you get the sound my car is making.....!!!

My fan Belt is quite tight so I'm going to check your website David to check it out and maybe adjust the tension a bit.
But that doesn't explain why the sound is starting at 40mph.

I really can't find where the sound is located under the hood, I could try something like Prop suggested, but at 40mph I'm told never to shut my eyes, so it will probably not work....
There is absolutly no sound or problems below the 40mph, motor is running smoothly.

The only thing I can come up with is the coolerfan.
Does it stop when there is enought driving-wind to cool the motor? Could it be that the fan starts freewheeling at 40mph and creating that "tsjirping" sound.

Tako
T.A. VanderVeen

Tako - Sorry, I assumed that you had an older car with a dynamo rather than an alternator. Since you have an alternator, the information in the article on my web site doesn't apply, belts on alternator vehicles need to be quite tight. That said, you could still have a glazed spot on the fan belt that is slipping under the conditions you described. I have not been able to get my tongue wrapped around tjsirping well enough to say it out loud, but even though some of my ancestors were dutch, I have never mastered the language (after 64 year, I can barely speak English). Cheers - Dave
David DuBois

>>> ...belts on alternator vehicles need to be quite tight. <<<

The book says that you should be able to deflect the belt about 1/2" with a firm thumb-push on its longest section.

By the way, I came up with a simple way to maintain tension on my fan belt when adjusting it. The alternator is located rather close to the head on the 1500, so I made up a wooden wedge that fits nicely in the gap. I gently pry the alternator out with a bar, insert the wedge, and check the tension. When it's about right, I tighten up the bolts. That sure beats having to hold tension with one hand while tightening hardware with the other. When done, I just toss the wedge in my tool bag until next time.

-:G:-
Gryf Ketcherside

TA

Do you have alloys e.g. Minilites or similar?

Check the TREs aren't touching the rims as the front wheels rotate...

A
Anthony

the way I adjust alts....

I all ways use a flat wreacking bar for construction demo work its about 3 inches wide and 20 inche long...with a hard curve at one end and a gentle curve at the other...just lever the alt in then tighten the bolts


but love the idea of a wooden wedge

prop
Prop

Ok, I've tried lowering the tension of the V-belt a little bit but it didn't help.

Anthony: I'm not driving on minilites but on wire-wheels....and they are not touching the trim.

Today I've noticed the Speedometer was reacting on the sound,when the sound starts at about 40-45mph, the meter is stabil, when I keep on driving this speed the sound stops and the "arrow" of the speedometer jumps up a bit, when the sound starts again the meter is stabil again....

I don't know how and where the speedometers measures, but could there be a problem?

I hope to make a video with sound tomorrow so I can show you all what I mean...

Tako
T.A. VanderVeen

My 1500 speedo cable 'partialy' failed such that it still drove the speedo but the needle jumped erratically at certain speeds. Also I could here a faint hard to describe noise. New speedo cable required is my bet
s lowiss

Sounds to me your speedo cable has got a bit dry. Try pulling the inner cable out and greasing it up 'could be all it needs. Gary
Gary

OK, that sounds really reasonable!
What is the best way to take out the cable? First I will try to grease it and maybe renew it when its really looking bad.

Do I heve to start by taking out the gauge or is there a better way. Where does the cable end can I find it myself without taking the car to the garage?

Pls advice me before I do something wrong I'm not that tecnical, just learning every day!!
T.A. VanderVeen

This thread was discussed between 05/06/2008 and 08/06/2008

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