MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: MGB Roadmaster
Posted by: BlownMGB-V8
Date: March 11, 2013 07:37PM

Max, on that relay the next thing would be to measure the current in the control circuit. It shouldn't be much, on the order of a couple hundred milliamps maybe so you could insert any cheap ($3 HF) meter into the control leg going to the thermostat switch. You could also unplug the relay and measure the voltage across the winding terminals, maybe leave that in place during a drive to see what it does. The other fan should handle the cooling needs. Anything other than full voltage or rated current indicates a problem and can be tracked down, possibly to a misplaced wire or a specific combination of things turned on. At any rate we are closer than we were. The clean contacts are a very good sign, meaning it isn't a overcurrent issue. We now know we have isolated it to the control circuit and there is a cause. Just a matter of tracking it down.

Brakes. PDWA? I got nothing. Poor Dumb Wretched Article?

Carb, I suspect you could be on to something, what does Steve have to say about it?

Jim


danmas
Dan Masters
Alcoa, Tennessee
(578 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

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Re: MGB Roadmaster
Posted by: danmas
Date: March 11, 2013 09:23PM

Max,

Which relay did you open, the one on the fender or the one on the powerblock?
Quote:
So.... Dan? Is there any way the 2nd relay that you added in is somehow backfeeding, or shorting, or something?

It's certainly possible, but if I actually wired it the way I intended, I don't see how. maybe someone else can look at the diagram (top of page 106 of this thread) and see if they can see a way. If it were wired wrong, it would stay on all the time, not just occasionally. How often does it happen? Intermittant problems can be extremely hard to track down. You may have to physically trace out the wiring to see if there is a wiring problem - pinched wire, miswired, etc.

Try removing the LH relay and pulling the purple wire as shown below and see if it still does it.

roadmaster fan RH relay isolated.jpg


Dan B
Dan Blackwood
South Charleston, WV
(1007 posts)

Registered:
11/06/2007 01:55PM

Main British Car:
1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl

authors avatar
Re: MGB Roadmaster
Posted by: Dan B
Date: March 12, 2013 11:38AM

Power Discs With Assist?


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: MGB Roadmaster
Posted by: MGBV8
Date: March 12, 2013 02:31PM

Pressure Differential Warning Actuator

[www.vtr.org]

I'm sure Max is right. I doubt its ever been touched.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: MGB Roadmaster
Posted by: BlownMGB-V8
Date: March 12, 2013 04:11PM

Wow. I'd never have figured that one out.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: MGB Roadmaster
Posted by: MGBV8
Date: March 12, 2013 05:50PM

Me either. ;)


danmas
Dan Masters
Alcoa, Tennessee
(578 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

authors avatar
Re: MGB Roadmaster
Posted by: danmas
Date: March 12, 2013 07:35PM

It's called a "Pressure Differential Warning Actuator" because it actuates a warning when the differential pressure between the front and the rear brake lines gets too high. On an MGB it's called a "brake failure switch."



kstevusa
kelly stevenson
Southern Middle Tennessee
(985 posts)

Registered:
10/25/2007 09:37AM

Main British Car:
2003 Jaguar XK8 Coupe 4.2L DOHC/ VVT / 6sp. AT

authors avatar
Re: MGB Roadmaster
Posted by: kstevusa
Date: March 12, 2013 08:10PM

I believe mine is called a 5/8" NSF Bolt. Nary a problem : ). hope I can feel a failure approaching?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: MGB Roadmaster
Posted by: BlownMGB-V8
Date: March 13, 2013 11:33AM

I believe it is entirely missing on my car. At least I won't have to rebuild it.

Jim


mowog1
Rick Ingram
Central Illinois
(1523 posts)

Registered:
10/17/2007 09:36PM

Main British Car:
1974.5 MGB/GT 3.9l Rover

authors avatar
Re: MGB Roadmaster
Posted by: mowog1
Date: March 13, 2013 08:10PM

Don't have one on my V8, either.


madmax
Max Fulton
Durham, NC
(186 posts)

Registered:
10/19/2008 07:45PM

Main British Car:
1974 1/2 MGB 1972 MGB 1977 V8 project 1972 B r 1860 cc

Re: MGB Roadmaster
Posted by: madmax
Date: March 14, 2013 08:37AM

DanM:

I replaced the one in the PowerBlock.

I don't have the PDWA in either the racecar (made no difference, btw) and my road car (Ted's front Willwoods.)

The rebuild kits are cheap and so because that's how the lines are made, I'll just rebuild it and stick it back. (The hard part of replacing it is coming up with a 7/16-20 3-way union to put the front lines into!) The rear is easy-- the OE union from under the floor, scrounged from a parts car, works perfect. :-)

M


madmax
Max Fulton
Durham, NC
(186 posts)

Registered:
10/19/2008 07:45PM

Main British Car:
1974 1/2 MGB 1972 MGB 1977 V8 project 1972 B r 1860 cc

Re: MGB Roadmaster
Posted by: madmax
Date: March 24, 2013 07:45AM

UPDATE:

Worked on the RM for a bit yesterday. To Wit:
a) replaced the PDWA, which was leaking out the switch (from the Front side). Couldn't rebuild the one in there-- it's the type they DON'T make the seals for! So, replaced it with one from a later car which was rebuildable. Ended up vacuumi bleeding the brakes. (Pressure bleeder wouldn't seal, dumped fluid all over the floor). Pedal is firm, but I wouldn't call brakes stellar, merely 'good'.
b) Aimed the headlights UP some. (Note: in this car, with those headlights, it actually meant on one of them to let the bottom OUT because the top couldn't screw in anymore.) Haven't driven it in darkness since, but I agreed with PJ that they were MUCH too close on the road.
c) Tried to shim the rack further (still some back/forth slop in the steering wheel). No good-- locks up the rack. I'm wondering if our remaining slop is actually in the collapsible column?
d) Cleaned and reoiled the air filter.
e) checked fuel gauge wiring (both sender and gauge are grounded). Checked sender itself (I was low on fuel anyway... :-) ) and found it old, worn and rusty (but the float still did!). Alas we didn't have one in stock, but I'd recommend a swap to a new one and see if that stabilizes the gauge.
f) put thread sealant on the front-most manifold bolt (pass side) which was leaking coolant. Not sure if it *should* be into the water jacket, but it is!


It was a beautiful day here, yesterday. Would have loved to go for a cruise but the carb/tune still isn't good enough to fully enjoy the car. Short bursts it's okay, but it shakes under the heavy foot.... :-(


One Build Note: Working on this car by yourself, well... sucks. I've usually worked on it as a "team/crew" activity, and (other than Jim) probably everyone else did, too? However, we SCREWED ourselves royally by doing this because we have TOO MANY situations where there are 'bolt-throughs" (cuz someone held a wrench underneath/inside, etc.) and you can't get those by yourself!!

Perfect example: brake master and pedal box. Two studs (NOT welded) hold the master. (It looks like maybe they WERE welded, but they ain't now!). Then four bolts and nuts hold the plate that THOSE bolts are in! In all cases we need capture nuts/studs, but if just ONE had been done, I could have handled the other. With neither done, I was unable to undo any of this and just had to "wing it" back together. (Super Glue a wonderful thing...)

(And, usual excuse: at the time-- No Brakes and struggling Yet Again to bleed tham-- I was not eager to Undo the whole pedal box assembly so as to make this more Loner User Friendly. So, sorry-- I just passed the buck. :-p )

Anyway, the conclusion is: Capture Nuts are our Friends! Let's install them more frequently in the future. :-)

$.02

Cheers,

M


madmax
Max Fulton
Durham, NC
(186 posts)

Registered:
10/19/2008 07:45PM

Main British Car:
1974 1/2 MGB 1972 MGB 1977 V8 project 1972 B r 1860 cc

Re: MGB Roadmaster
Posted by: madmax
Date: March 24, 2013 07:50AM

ADDENDUM:

Fan ran yesterday on drive home. (Rem: "beautiful day?" :-) ). It shut itself off. (This is now new relay on powerblock.) I'm not saying it's fixed (I have no reason to believe it is!) but if it doesn't "stick" on, we can't really chase down the problem... :-/

M


mowog1
Rick Ingram
Central Illinois
(1523 posts)

Registered:
10/17/2007 09:36PM

Main British Car:
1974.5 MGB/GT 3.9l Rover

authors avatar
Re: MGB Roadmaster
Posted by: mowog1
Date: March 24, 2013 10:27AM

Thank you, Max.


Dan B
Dan Blackwood
South Charleston, WV
(1007 posts)

Registered:
11/06/2007 01:55PM

Main British Car:
1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl

authors avatar
Re: MGB Roadmaster
Posted by: Dan B
Date: March 25, 2013 11:59AM

Maggie in Roadmaster.jpg

This is a picture of one of my daughters enjoying the car at the WVBCC Christmas party last year.



lawnvett
PJ Lenihan
Winston-Salem, NC
(477 posts)

Registered:
04/29/2009 11:37AM

Main British Car:
74 MGB-GT 3.4 V-6 crate, 5 spd

Re: MGB Roadmaster
Posted by: lawnvett
Date: March 25, 2013 04:38PM

Thanks Max and give me a shout if you need a helper.


Dan B
Dan Blackwood
South Charleston, WV
(1007 posts)

Registered:
11/06/2007 01:55PM

Main British Car:
1966 TR4A, 1980 TR7 Multiport EFI MegaSquirt on the TR4A. Lexus V8 pl

authors avatar
Re: MGB Roadmaster
Posted by: Dan B
Date: March 27, 2013 09:09AM

Which is faster?
roadmaster jet.jpg


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: MGB Roadmaster
Posted by: BlownMGB-V8
Date: March 27, 2013 10:47AM

It seems like Max had a question about possible play in the steering column.
Yes, this is a possibility. I have recently read some good advice on column rebuilding and there is one thing we may not have done when we worked on the column, and that is the step of heating the slip joint and pumping hot melt glue into the holes. I can't say for certain that we did not do it, but I can't say for sure that we did either. So if there is play in the column it's a pretty safe bet that is the cause.

Jim


Citron
Stephen DeGroat
Lugoff, SC
(367 posts)

Registered:
10/23/2007 09:43PM

Main British Car:
1970 MGBGT V6, 7004R, AC, matching trailer 3.1 liter

Re: MGB Roadmaster
Posted by: Citron
Date: March 27, 2013 03:26PM

I think play that involves the slip joint will be only in the in/out movement.

steve


mowog1
Rick Ingram
Central Illinois
(1523 posts)

Registered:
10/17/2007 09:36PM

Main British Car:
1974.5 MGB/GT 3.9l Rover

authors avatar
Re: MGB Roadmaster
Posted by: mowog1
Date: March 27, 2013 05:59PM

Maybe we could sweet-talk Gerry Masterman of Louisiana to rebuild the column for us?!
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