MOT Passed!

[johnnyj]

Hi folks

Just sharing some good news - my TR7 passed its MOT after years off the road. Hurrah! It is actually exempt from the test but I had it done anyway, mainly because I wanted someone to check my work plus the feeling of having the certificate in my hand would feel good.

However, the car does have some issues ("the lord giveth, the lord taketh away"!!!) which became apparent on the MOT shake-down run.

1. The MOT station has a very steep ramp down into the workshop, and you have to reverse out. The car just wouldn't go up the slope and I had to be helped by a load of people pushing (me: "pleeeez don't push on the nose cone, tops of wings etc"). As soon as the car was under full load with the right balance between clutch bite and revs, the revs dropped to nothing and the engine stalled. Tried multiple times and it was very odd - not me getting the clutch etc wrong, I know how to reverse up a slope! It was very odd. The reverse element could be a red herring, though - haven't tried going up a steep slope forwards yet. But it drove home fine.
2. The tickover is a little too high, but I can't get it low enough unless the throttle spindle between the carbs is physically pushed back against its stop by an almost imperceptible amount. When you let go, the revs rise again. I have added an extra return spring to pull it back, but to no real effect. The carbs are brand new and if I back off the idle screws on the carbs any further, the screws actually clear the idle cams completely.
3. There's a small oil leak from somewhere - will have a look underneath.
4. One of the nearside brakes/hubs is a bit screechy - sounds like something fouling a dust shield.
5. And finally, the damn water pump is still leaking from the escape hole on the side of the block. That's after fitting a fully refurbished water pump supplied by a well known refurbisher; that then failing; rebuilding that pump with a kit from a well known TR7 parts supplier; that now failing. I followed the repair ops instructions exactly when refitting both times.

Some thoughts:
1 & 2 may be connected? Carbs running lean, perhaps?
1 & 4 may be connected? Perhaps brake grabbing in reverse?
5 Really at a loss to know what else to do, other than to fit a brand new non-refurb pump. But I am wary that this could go on forever with the car constantly rejecting water pumps. I guess it makes sense to look at this and the carb issue at the same time, though (carbs off = get at water pump)

Any thoughts would be very much appreciated and in an ideal, post lockdown world I would be so delighted if anyone would be willing to come and help. I am kind of at that stage where I could do with another more experienced pair of eyes, ears and hands to get it over the line.

Hope everyone's well.

All the best

John

[Cobber]

Re the waterpump: bin the bastard of a thing and convert to an Electric water pump, there has been some discussion about the merits of EWPs made by Davies-Craig here on this forum, search EWP or Davies Craig an you should find the posts.
I've got one waiting for me to getting around to fitting it to my car (mine hasn't shat itself yet so haven't bothered yet!)

[johnnyj]

I would Cobber, but I want to keep this car original. If I have to go down the EWP route, then so be it...

[Cobber]

Keep it original and keep the original design faults and the original bean counter's compromises

[Beans]

New or refurbished water pumps have a habit of leaking a little for the first few kilometres (up to 100 or so in my experience).
That's the graphite seal bedding in. After that it should be fine.
Though longer periods of idleness might start a small leak, which again should disappear after some driving.

[Beans]

Could it be that the choke's cam is set incorrect en is (just) intervening with the throttle?

[busheytrader]

Ive found that new brake pads can be noisy when bedding in, even when not applying them, as they scrape off the top layer, especially the EBC green stuff etc type.

Amazing how noisy the brakes are with bare metal floors and no baked bean tin lids in them.

[FI Spyder]

I'm under the impression that a slightly high idle that can't be adjusted out is due to a small air leak in the intake. This can be worn throttle shaft bushings which have to be drilled out and new ones pressed in. We have a carburetor guy in our car club that does carb repairs for the club members. Saw some in the process when we did a tour of his home garage a few years ago.

[johnnyj]

Thanks folks, useful info.
- Water pump. I'll wait to see if it lessens over time, then;
- Brakes. Ditto!
- Carbs. The choke cam/throttle stop clearance is fine, double checked today; I was wondering about air leaks, too, although shouldn't be a problem with the bushing for the spindles as the carbs were brand new refurb stock from a TR7 specialist and have only done the distance to the MOT station (6 miles). You've got me thinking about the rubber mounting blocks - I used the best used ones I could find, rather than new ones. Maybe they are leaky.

That just leaves the stalling under load. I reckon it might be slipping clutch, but somehow it didn't feel like that. I wonder if a massive amount of air is getting into the carbs at high load revs, from the same source as above, thus making the mixture weak at the worst time? The other thing I wondered was perhaps brakes snatching or something?

Do keep the ideas coming, as these issues are the only things between me and a perfectly sorted car.

Thanks again, much appreciated.

John

[Beans]

Spray brake cleaner or start help on all suspect areas with the engine running.
If nothing happens there's no problem. If the revs rise you've found an air leak.

[Rich K]

Hi John, are the rubber breather pipes to the carbs in good condition with clamps fully tightened as these can be a source of air leaks.

[johnnyj]

Hi Richard, yep, they are brand new with new clips.

I did have a look at the carb mounts earlier and the front one has some cracks which open up when the carb is pushed/pulled a bit. I'm always wary of chasing red herrings, though, as the idea of a vacuum leak was only my shot in the dark hypothesis! I guess I need to try to replicate the fault and work out what's actually happening overall (referring to the stalling under load thing, rather than the carbs not going to low enough idle).

I just remembered that at the MOT station, the car struggled to get off the brake rollers (and stalled) going forward, so I think I can rule out that fault being solely associated with reverse. That's one bit of the jigsaw!

All the best

John

[FI Spyder]

I seem to remember some one posting that they removed their rubber carb mounting blocks (using gaskets) thinking they didn't need them as the MGB's don't have them (?) as they are thermal blocks (?) and may be just for the most extreme of circumstances. Any one did that or remember that?

[Beans]

Are you referring to fitting alloy carburettor mounts?

[johnnyj]

Ok, I did some investigating today and confirmed a couple of things, solving one.

If I spray carb cleaner on and around the front carb, the revs drop. I seems to be most prevalent around the throttle spindle (front end), although I note it has been re-bushed. Certainly there is a vacuum leak from somewhere, which accounts for not being able to get the idle low enough. More investigation needed, I think, but I am thinking I should probably change the rubber mounts. Are the new ones available still poor quality?

If the throttle spindle bush/hole is causing the problem, I will be massively annoyed as the carbs were very expensive, bought from a specialist and purchased as reconditioned.

As regards the stalling under load thing, I may have had a breakthrough. While working on the the above, I noticed that if the engine is physically pushed sideways, it would stall in exactly the same way as happened at the garage. "Hmmmm, that's odd" I thought. I had a brainwave and wondered if something was shorting out when the engine moved, and found the -VE spade connector to the coil had come adrift. It was "just" making contact with the terminal when the engine was idling, but when the engine rocked slightly with increased revs, it was moving away from the terminal and not making contact. Re-attaching it confirmed things - after doing that the engine couldn't be stalled by pushing it. Solved? I hope so.

I'll keep you posted.

John