MGB Roadmaster

[BlownMGB-V8]

Max, the relays had been changed out. Not the original relay. Don't know about the rest. Mike Moor and I put the sensor bulb inside the radiator hose to reduce hysteresis. The switch has always seemed to work correctly after that as far as I can tell. We have at various times resorted to pulling the one relay when parking the car. For whatever reason that one has a problem but the other one doesn't. Are both circuits identical?

Jim

[danmas]

Here is the wiring diagram for the fans. They are nearly identical.

[madmax]

Thx, Dan.  

I'm presuming the "X" indicates the "old" wire to the 2nd fan?  Or is it indicative of a 5-th prong?  (Or both?)

If the points were "sticking", we'd transfer power, regardless of whether it was triggered.  When I pull the fuse, removing the power, does that "unstick" the relay and thus why it didn't come ON again?  One would think, if we had a problem with the sensor grounded, then it WOULD just come on again, but it didn't!

I'm going to proceed with this logic and pull the relay out of the powerblock and give it a look-see...

M

[BlownMGB-V8]

The only other cause I can come up with is if somehow there is a leakage current somewhere that is not quite enough to turn on the relay but is sometimes enough to hold it engaged. This might happen with a pinched wire on the ground side. But I don't really buy that theory.

Jim

[danmas]

Jim and Max,

Every answer I come up with falls short too.

Max,

The X indicates a wire that is not used. The LG/R wire is wired into the panel to operate a "fan on" indicator lamp, which we didn't use. It comes from the "fifth" pin of the relay. I don't know what was done with that wire - cut off, looped up for future use?

Here is the way it was wired before Jim and I added the extra relay. As you can see, two fans put quite a load on the relay and the fuse.

[BlownMGB-V8]

Curious, I don't recall, was the fan staying on before the rewire? Guess it must have been. But after the rewire it was the new relay circuit that was sticking, right? Could be a clue there somewhere.

Jim

[danmas]

Jim,

Before we added the extra fuse/relay, the fans were blowing 30A fuses - not good! I don't know if the fans were staying on or not - I think they blew a fuse instead so we wouldn't have known if they would have stayed on . If I read Max's post correctly, it was the RH fan that was on, which is wired to the original circuit. It may have been that the LH fan would have been on too if the breaker hadn't fallen out.

I've looked at both the original and the modified diagrams, and I can't think of any miswiring that would cause the problems we're experiencing. Any errors I can think of would either cause the fans not to run at all or to run all the time, not stick on randomly. Having said that, I have been known to screw up on occasion in some rather "creative" ways.

The only way we'll resolve this is with some "hands on" trouble shooting. I've exhausted my meager mental capacity to troubleshoot from a distance.

[Dan B]

Time for an injection!

[flitner]

We have relays that stick on the hydroboost pumps at work all the time, a simple flick will set the contacts free, also when pulling them from the weatherproof socket under the hood will release them, these are Bosch units and the hydraulic pump in no way draws what the fans will. Monthly we might walk by a truck with it just buzzing away. Might suggest hooking it to a switched powe source on the accy side so the can runn with ignition coil etc. is off.
Please excuse the bad text, phone is acting up.

[madmax]

Jim, Dan, John:

Thx for all replies.  You all seem to understand what I've reported.  :-)

I do believe it's up to me now to pull that relay, replace it, and pop open the old one and just see what's going on.  (Pitting, maybe?)

DanM:  if we wanted to use John's idea of making one of the wires Ignition dependent, how do I do that on that circuitboard?   It's all wired so nicely, I'd hate to screw with it!   :-)     Any thoughts on a way to divert the power feed (for either the fan OR the relay) so that the igniton would have to be on?


Just to muddle things further:  I was wondering If we could just wire in a second sender unit for the other fan and then put it back on the 30 A fuse?  The first fan would trigger at 185F (say) and then the second one at 195F.   Without them both trying to spin up at the same time, I should think the one 30A could run that circuit.    The worry, though, is that maybe one fan never gets used...?  

Spitballing.

M

[madmax]

NEXT TOPIC:   the Hit List

The following are the list of areas that I feel need attention on the Roadmaster.   They are listed in a priority that reflects (to me, at least) the affect on the level of enjoyment of the car, the safety, and then just the fact that they "aren't right".   There is also some maintenance stuff I didn't get to..  :-(


Roadmaster, Mar 5, 2013

TUNE ROCHESTER
Fan wiring
Recalibrate speedo
Tach wiring
Fuel gauge wiring
Aim headlights (up)
Coolant leak on manifold
Steering slop
Needs antenna
Add passenger side mirror
Heater temp
Interior lts inop
Wipers "squawk"
suspension creaks and groans
seatbelts difficult to release (PJ)

Other things to do/record:
Leakdown & compression test
Front wheel bearings-- check grease
Gold or Petronix coil


JIM/BILL:   before the Driving Season starts, how much of this do you want to tackle?   I've already had My Fun with the car and don't want to deny others of their chance to get dirty.   :-)  

If the car is headed to either Florida or California, it really needs to be fully tuned.   And then it would also be nice to have some working gauges.   But, those two things being fixed, the car is probably no worse than anything the rest of us are driving.   :-)

Let me know your thoughts.    It's getting limited usage in my hands--don't like the uncertainty with nailing the pedal, and I have no idea when I'd ever find time to work on it again.    [Racing season is starting up.    ]

M

[BlownMGB-V8]

I put a two stage switch (Volvo) on Edith's 3.8L TR-7 and it works great. Finding a switch with the right threads will be the trick but they are out there. (1/2" NPT I believe). There is an unused (wrong) sensor on the intake manifold. In fact I believe there are two bungs so it would be possible to install two separate switches.

Wiring it to run only with the ignition on will eliminate the problem with running the battery down and the car does not run hot at all so heat soak should not be a problem. (If the fan is running as you walk away there is a problem)

The relay on the fender was the one we were having to pull on the powertour.

Has anybody looked at how the original application is wired? (2002 Camaro I believe) What relay was used there?
http://www.autopartsnetwork.com/catalog/2002/Chevrolet/Camaro/Electrical-c-_Lighting_and_Body/Engine_Cooling_Fan_Motor_Relay/Four_Seasons/36009.html?filter=make:Chevrolet_model:Camaro_part%20name:Engine+Cooling+Fan+Motor+Relay_brand:Four+Seasons_sku:36009_&fpi=9k2D2k9PsxMGIc6NwiYyHM2wstsBhFwt4gj2rg3Ph0M=

Carb: Can anybody start working on the TBI angle? Seems to me if we had a TBI on the car the tuning would suddenly get a whole lot easier and we do not seem to have one single Quadrajet expert in our midst who can make this thing run right. Either that, or maybe we should send the car up to live with Richard Moor for a couple months or more if he could fiddle with it some. Just suggestions, I seem to be more tolerant of bad engine behavior than most. And it really hasn't toured the northern loop yet.

Gages: Isn't it about time we bite the bullet and install a new set of gages?

The weather should break soon. Do we know where the car is going next, or how it is getting there? I think we should route it up towards the Detroit/Chicago area. We have a heavy concentration of contributors up there and the car could spend the entire summer up in that area without any trouble at all.

I would suggest that we could shuttle it to Florence for the Maxton Mile get together at the end of April and then on up to the northern loop, perhaps to Richard if he is willing to try tuning it. Or, maybe we could find a way to get it to Richard first? It really doesn't have to be here for Maxton, and I heard there were plan to take it out to Omaha? Maybe it should go north and make the rounds up there between now and Omaha.

Jim

[madmax]

Another problem!

LOST BRAKES on the drive into work today.  (Here I was thinking I might get to look into the coolant leak after work.  :-/  )

Steve showed up here in February with a *nearly* empty rear reservoir (which is front brakes.)  We had to pressure bleed after doing the rear diff work.   Thus, at that time (300 miles and 3 weeks ago) the reservoir was full.   We tightened some fittings, thought maybe we'd found a slow weep....

Well, front reservoir is at level, but rear is EMPTY today.   So, we're leaking somewhere that we still haven't found yet.   :-(  

<sigh>  

M

[BlownMGB-V8]

I seem to remember the caliper hose on the passenger's side didn't look exactly right for some reason. Nothing I could identify but you might want to look at it.

Jim

[danmas]

Max, et al,

Changing over to ignition dependent is not very hard, just physically getting to the powerblock wiring to make the changes may be hard. A couple of wires on the powerblock will need to be cut and splices made. Need to be very careful not to cut the wrong wire, because that would be a bear to fix.

Here's the diagram.  The relays will still get power from an always hot wire but will be controlled by an ignition keyed power. Of course, if the relays stick you still have a problem.  Changing the circuit so that the relays are only powered by ignition keyed power source will be a bit of a problem, as the main power relay does not have the capacity to handle the extra fan loads (we'd be back to the problem of having one relay handle the 30 amp fan loads, plus the existing loads).

I think we need to find out what the problem really is before we make changes.

[madmax]

Dan:

I've ordered in another Bosch relay of the part # you specified and will swap that out and then look at the old one.  


RE:  Carb.   Thought occured to me:  did the car have transitional issues always, or has this developed?  And in which case, is it maybe related to the (3?) times the car ran out of gasoline?   I'm wondering if we sucked up some crap into the secondary circuit...   :-/  

Honest opinions here:  how driveable was it on the Power Tour?  I mean, full usage of the pedal, no hesitation, no pinging, no surging, no shaking?   These are things it is capable of doing NOW.  

Thx.   Trying to find one more day to dedicate to fixing these things, but it's tough.   I spent two entire weekends either on the car or with the car (BMTA) and the rest of my life has fallen behind.   :-(

Cheers

M

[lawnvett]

Max,
I had a fuel pump failure shortly after running out of gas last Aug., I then only drove it one block to a hotel, after that it was trailered to Ricks.  Prior to the out of gas experience RM was running well did not have any of these problems:  "full usage of the pedal, no hesitation, no pinging, no surging, no shaking".    Hope this helps.  
I also had no fan issues.

PJ

[MGBV8]

HOWEVER--- given a long enough straight, I would think Roadmaster could hit 140. If anyone had the balls to TRY... :-)

Felt stable to me. I'd hold it to the floor for a mile.  Just takes a lead foot & a touch o' insanity.  

[BlownMGB-V8]

Has anyone looked at the specs on the original application relay?

Jim

[madmax]

All, esp. DanM and Jim:

Swapped the relay today.   It was a 30A "tyco electronics" and I replaced it with the Bosch # specified by DanM.  

I opened up the relay-- gorgeous.  I set it on a test bench and it worked perfectly-- no sticking, trying all combinations of removing power, removing ground, checking continuity, etc.  

So.... Dan?  Is there any way the 2nd relay that you added in is somehow backfeeding, or shorting, or something?

I, too, would rather NOT change the wiring until we are sure what the problem is.   I'd have bet money on the sticking relay, but having opened it up I just don't see it.   (I must have clicked it 50 times-- perfect.)   Even manually clicked it to feel for any chance of "sticking" and it's fine.  Looks brand new inside.  


RE:  brakes.   I have a rebuild kit for the PDWA and will do that as a matter of course.  (I'm doubting it was ever done before?)  In the process of removing that I'll be able to look at the lines/fittings.   There are some old lines/rusty fittings and I'm wondering if we have a cracked line.   (There are drips on BOTH the "down" lines, though it's the rear reservoir (for the front brakes) that goes empty.).   Thankfully, just topping up the fluid in the reservoir brought the brakes back (~ish) so I didn't have to pressure bleed.  (Don't want to have to deal with THAT hassle again until everything has been checked.)  


RE:  carb.  I'm tempted to think it's possibly crap sucked up from the running dry "events".   I've given it 4 tanks of premium at this point and have not experienced any of the pinging or the violent shutdown issues since then.   (Or, certainly not as much as it did at first, which was always.)   I'm not sure WHY this is, but when in doubt I'd like to blame the timing.   :-)

More at some point...

M

[BlownMGB-V8]

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]

Max,

Which relay did you open, the one on the fender or the one on the powerblock?

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.

[Dan B]

Power Discs With Assist?

[MGBV8]

Pressure Differential Warning Actuator

http://www.vtr.org/maintain/pdwa.shtml

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

[BlownMGB-V8]

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

Jim