KM

Thanks for all the advice and suggestions. It was the relay at fault. I am still puzzled as to what was going on but the switched positive had 12v until there was a load, ie the solenoid, on it.

glang - yes

Its a Tr4A with negative earth. The overdrive has stopped working. The attached diagram is my wiring circuit. The relay appears to work. It has permanent 12v on the brown lead and switched 12v (ignition) on the white lead. In the attached diagram the white comes in at the top and the brown from the left. In 3rd or 4th, with ignition on and with the column switch in the on position, there is 12v at the switched relay output (the central pin - Yellow and Purple wire) for the solenoid but the solenoid doesn't move. If the solenoid is shorted (12v directly to the yellow/purple) it fires immediately. I have tested all the wires for shorts and breaks. The control column switch and the transmission switches work. The relay makes a definite click when being de-energised as opposed to being energised. So what I need help with: Is this a relay problem or something else?

Its all back together and runs fine. Thanks for all the advice. One last question. How tight should the nylocs holding the diff on be? Since they are nylocs I guess there is no torque setting so perhaps so many threads visible?

Thanks Gavin & Colin. Will update in a while. Lots of degreasing and painting to do first.

The trailing arms are off to replace the bushes.On the left side the bushes were nicely centred but on the right side they are offset. Am I going to have a tracking issue if the right hand side has centrally positioned bushes? Also what is suitable lubrication to help insert new bushes? Normal grease? Will this affect the bushes long term? Rubber ones.

Roger, yes I do. If the power has been on and I brake you can feel the drive train go from one end of the slack to the other making smooth driving tricky. Probably more noticeable after braking then accelerating. I have CV joints on the driveshafts so it isn't a UV issue. The prop shaft has no slack in it so it isn't the UV joints there.

Its a Tr4a with CV joints on the rear axle. There is no slack in the prop or the drive shafts. There is however some slack in the diff but I don't know whether this is normal or not. The attached pic shows the angle one wheel goes through with prop locked and the other wheel on the ground. See the two chalk marks. When driving between power on and brake on or visa versa it feels like the slack is excessive. Can anyone tell me this is normal or not?

An update for all those kind enough to offer advice: the nearside wiper 'box' (the spindle that has the wiper arm on one end and the gear at the other) is solid and even with a pair of pliers won't rotate. Anyway the gearbox is nicely greased now ready to be be re-assembled when the spares arrive.

My wipers are failing, they are very slow and don't return to the parked position so I have taken everything apart and given it a good clean. New motor brushes on order although plenty of depth in current ones. The gears had a nice coating of grease however the square channel for the reciprocating part looked distinctly oily. Does anyone know how it should be lubricated?

I put my foot down occasionally but it isn't thrashed, it's always warm before any hard acceleration. It does have a mild cam (next up from standard). There will be radio silence for the next week as I am away but will report progress on my return.

Any recommendations on a head gasket? Rimmers are selling standard ones for £21 and uprated ones for £110 which is a big difference. 

It doesn't appear that the cooling system is being pressurised to any great degree. It had two trips of about 50 miles each and lost about a pint. My previous experience of significant head gasket failure is that the water leaves the radiator very quickly. It doesn't appear to be in the expansion bottle and if it did get there would it not be sucked back as the engine cools? How do you check the coolant for combustion gases? If re-torquing does it I would probably replace the gasket anyway. Unfortunately I don't have the tools for a leak down test however the results of a compression test are: 1: 196; 2: 192; 3 188; 4:190 which to me doesn't help. The plugs all look similar, see attached. #1 is over the large grommet and #4 over the small grommet.      

And it's not using oil any more than usual so the leak is slow.

I have a Tr4a and yesterday had to put a pint of water in the rad to top it up. I didn't notice any oil in the rad at this point. It was driven about 100 miles yesterday. No obvious change in performance. Today I checked the rad to discover an oily emulsion and clear signs of oil in the rad. Again it took about a pint of water. There is definitely no water in the oil. Removed rocker cover where there is standing oil and clearly no water. With hot oil and 2,500rpm it reads 60 to 70 psi on the oil pressure gauge. The engine was re-built about 20,000 miles ago and the head was replaced as the old one had a crack. The temperature sticker was put on the left side on the block. It has never overheated. What I need to know is what the likely cause is before I decide whether I can attempt to fix it or it needs to be seen by an engine specialist. Head gasket? Crack in head, or worse block?

Colin, I have a 4:2:1 exhaust but no other performance changes. Are you saying the timing should be retarded from the factory 4 degrees?

Have settled on 7 degrees, mostly 97RON.

And so I get there in as few iterations as possible what additional advance is likely? Less than 5 degrees? More? Thanks in advance.

Just to clarify, when you say the above do you mean when it starts to pink?

I have a Tr4a which I set the timing at 4 degrees BTDC as the static timing and then advance it slightly after a few drives. No science involved. Is there a recognised static timing advance for 99 or 97 (or even 95 when desperate) octane fuels? If not how should the correct timing be arrived at. My crank pulley has a nick to show TDC but nothing else in terms of angle marks.