MGB GT Water pump swap

The water pump on this car was making a terrible noise and there was an obvious spray line across and inside the bonnet in line with the pump bearing. A clear sign that its been leaking. I drained the coolant by disconnecting the bottom hose but I didn't drain the block- probably a mistake (see on)

First step was to loosen the alternator mounting bolts

 ...and the clamp bolt on the slotted strap bracket

 ...so that the alternator can be swung inwards and the old belt removed. This will be replaced.

The pullet is held on by 4 7/16 bolts with spring washers

 Once the 4 bolts are out the pulley comes off. I cleaned it up and resprayed it where the powder coat was coming off.

Remove to hose

The pump is held on by 4x 1/2 inch studs, 3 are the same length and one is longer. 

Unscrewing pump mounting bolts.

Long bolt next to new pump. The long bolt passes through the thickest point of the pump and so penetrates only as far into the block as the shorter bolts.

The long one goes through the widest  part of the pump. All bolts needed cleaning and the lower ones de-rusting! In addition the forward alternator hinge bolt passes through the pump and so has to be removed.

Front alternator hinge bolt must be removed to free the pump.

The old pump was removed, which is when I discovered I should have drained the block as there was more coolant to be released once the pump was off! Its gasket could then be pulled free. It wasn't in good condition

Old gasket was decidedly dodgy

New pump compared with old.

Refitting is as they say the reverse of dismantling. You need to clean all mating surfaces carefully so that the gasket can seal. I didn't encounter any problems.

Refit top and bottom hoses

Pump on- refit pulley and alternator belt- check and adjust belt tension.

Refilling with coolant has to be done in two stages: Add coolant to the overflow tank to at least half full. Remove the block top-up plug and fill with coolant to the base of the plug threads. Note that you have to fill slowly as the liquid has to find its way down. Fill and wait for it to settle then top up again... repeat.

Start the motor and run it until the top hose becomes hot, then stop the motor and repeat top-up as described above.

MGB SU Carburettor HIF4 dashpot/piston drop test

Drop Test
Once the piston and dashpot sections were free I cleaned them up so I could perform a drop test. This gives a general idea of the piston wear. As shown here the piston is put in the cover and a small nut and bolt fixed temporarily in one of the mounting holes. The trick is to put a large washer under this bolt head so that it overlaps the  edge of the dashpot cover and will stop the piston dropping onto the floor. If you use a metal washer you should be able to get an audible click when the piston drops and this helps with timing.

 Unless the  air bleed holes are blocked the piston will just drop without resistance. If you have some 6mm bungs then use them- I found that the end covers from filler gun cartridges fitted perfectly- but you have to find the sort that aren't ridged all the way down. Its then just a matter of inverting the dashpot and timing how long the piston takes to drop onto the washers- I had to use fibre washers to get them large enough which took away the nice "click" and made timing trickier but it was OK with a bit of practice. My piston dropped in 6.5 secs, just within the 5-7s window cited for carbs of this size. Slower dropping could mean oil or other obstruction on the sides (so clean it and repeat); faster probably means the piston is worn and needs servicing.

Cartridge gun caps used to block air holes

King pins swivel axle and bushes

I bought the MGB as a usable, running, legal and roadworthy car. Well its running (just) and legal, but that last one does stretch the trade descriptions act a little. Anyway this means I'm going to have to do more work on it than I had envisaged. One complication though is that for various reasons; largely to avoid annoying the residents, I have agreed not to put any more dead and immovable cars on my drive. This means that anything I do on this car has to be done in one day- drive-in and drive-out. Bit of a problem for me as I tend to work very slowly....

I don't think there is any way I can strip the stub axles, remove kingpin bushes, clean, renovate and refit with new wheel bearings in a single day. Even more so as domestic taxi arrangements often shorten my time available anyway! The solution is to use exchange units... but (glutton for punishment) I don't really want to do that, I wouldn't learn as much about the car, so I would like to do this myself. The solution to my mind was to buy two used stub axles  and a single hub (Andy Jennings MG Spares) so I can recondition them- effectively to prepare my own "exchange unit" before fitting it to the car. This is really a learning curve-it keeps me off the streets (?) but I'm not going to pretend its cheaper- in fact many king pin kits are more expensive than the exchange parts from MGOC - and that's my fallback position if this all goes pear-shaped! However, this approach means that I will be experienced and tooled up for this particular job ... and although this is my first kingpin swap in an MGB, its actually my fourth overall so its probably now worth making it as easy as possible.

I received the two used units promptly and set about cleaning them up. They came with top trunnions and dust-shields. I stripped the kingpin castellated nut and removed the kingpin and trunnion, detaching the dust-shield. Very (very!) mucky but solvent spray followed by detergent bath did make headway.

Stubaxle rear- lower O ring for Dust shield location.

Some headway with cleaning the part

Unfortunately cleaning revealed that at least one of these axles had a problem. Obviously they are not new parts so some signs of use are likely. However the offside stub was badly scored and seems to have had a loose bearing at some point. I don't think it will be usable.

Taper section O/S stub axle badly scored.

Andy was very understanding about this, apologised for the quality of the part and sent a replacement.

I had wanted to use a bench press in order to remove the existing bearings- largey because I now own one! However I was defeated by trying to mount the stub axle securely. It's a very awkward shape and I couldn't get a clean, safe line for pressing. If anyone knows how to do that please let me know. Anyway I reverted to plan "B" which was to use a draw-bolt threaded through each bush in turn as I have done in the past. The usual approach here is to use a suitably sized socket to press the bush, but sockets are always rounded  at their ends and any size transitions are sloped. This means that a socket tends to either slip off the top of the bush, or expand it as its trying to push it out. Once the bush is pushed below the lip of its housing this is no longer a problem,  but it can make that initial push quite tricky- and its definitely problematic when refitting. To avoid this I made up the following two adapters that can slip inside the bush for positive location and have a 90 deg shoulder to press on the  bush. 

Press adapters as made; Large bush 23/26 mm, small bush 23/21 mm

They are sized to slip down inside the housing keeping everything straight as the bush is removed.

Press adapters fit into the relevant bushes- pictured after bush removal! 

These were assembled onto a draw bolt (M8 studding) again using appropriate sockets to pack the thing out. Obviously you need a larger socket on the bush-accepting side and a smaller one on the pressing side. The assembly is shown below- using the removed bush to indicate its position. My drawer bolts are M8 studding but I'm using the roller bearing/thrust washer assemblies from a Draper press and pull kit which can be bought as spares.

Positioning the assembly really depends on where the sockets will locate firmly. I found that the large bush was best pressed inwards, and there isn't enough room for a really deep socket to be fitted there. This meant that the last few mm had to be tapped out with a hammer and drift on the push adapter, but luckily at that stage the bushes were pretty loose and came out easily. The smaller bush could be removed by pressing it outwards and there is enough room for a deep socket in that position. The draw bolt and adapter in use is shown below. 

Using a draw bolt to remove the bushes

This system worked really well and removed all bushes in pretty short order. 

I cleaned up the rest of the parts, one point of note is that one of the dust shields turned out to be partially home made. It will need some repair but seems to be functional. However, I will use a bona fide part for the rebuild if I can get one. I treated both stubs with metalmorphosis and then sprayed them black- I also treated the spare hub I had obtained- taping over all threads and holes- as well as any mating surfaces that shouldn't get paint on them

Both stubs and a hub repainted.

I bought a partial king-pin kit from Ebay- I needed to chase up various other bolts and seals but managed to assemble a complete set for both sides, with new trunnions and bolts top and bottom for rather less than the cost of a new kit. I will use the adapters to fit the new bushes too, but I may need to make an additional piece for the other end of the bush so as to ensure any pressing forces are exerted in a straight line and don't  let the bushes bulge outwards too much as they are inserted.

Insertion press kit as made

I made the kit as above where both adapters will slip easily into the bush- they need to be smaller in diameter than the kingpin as you don't want to get them caught up should the bush bulge inwards during fitting (as it probably will). The larger diameters were made to slip inside the housing smoothly so that they will hold the bolt central in the socket as the bush is pulled home. One adapter is pressed by a socket whilst the other is free to slide along the draw bolt. I used a short length of rubber tubing to hold it against the bush and let it slip along the bolt as the bush moves into place. Sorry to make heavy weather of this but I  hope the diagram below helps!

The adapters were both made to the same dimensions in each bush- if you get 26 and 23mm silver steel the the larger dimensions need pretty much no modification so for the larger bush adapter dimensions* A and B are 26 and 23.5mm, whilst for the smaller bush they are 23 and 20.5mm. Length isn't critical as long as the combined lengths of the narrower sections is less than the length of the bush!
*These are appx I will measure properly and amend asap

With these adapters I still needed sockets to press on both ends- a large one to sit on the outside of the housing and a smaller one that could be pressed in with the other end.  This meant that both bushes were best pressed in from the middle of the housing in an outwards direction since the outer surfaces are flat and smooth and the socket fits well there. When making the adapters, its really important to get a sharp 90 deg step on the pressing ridge, any chamfer here just bells out the end of the bush and it will not fit in like that.  I found these worked well. Using both press adapters the pull bolt is kept centred in the hole and the bushes press in easily.

New bush- oil grooves on one half only and no open ends.

 When fitting a new bush the manual states that the open ends of the grease channels should face towards the stub axle- I suppose to ensure that old used and excess grease is pushed up into the dust tubes where it might still do some good (?). The grease grooves in my new bushes had no open ends and  were only present on one half vertically- as in pic above, the grooves stopped half way down and before the top of the bush. Luckily the instructions also say that the split in the bush should face forwards (i.e. away from the stub axle and towards the wheel). This positions the grooves towards the dust shield side.

Positioning bosh, split faces outwards and grease hole in bush is in line with the nipple hole in the axle

Pressing in the new bush using the adapters

nearly home

in position, bush sticks up inside the axle but is flush with the recess on the other side.

The bushes are pressed in flush with the external surfaces of the housings and protrude a little internally. The remaining bushes were fitted similarly and without problem- the most fiddly part was making sure that the sockets had a fine seating on the stub axle and in most cases it was actually easier to press the bush home from the inside of the stub axle towards the outside as this gave a good seat for the large socket - see below...

Reaming is simple if you have the right tool and I got this two step reamer from MGB Hive- worked very well. As with any reamer- use lots of cutting oil and turn in one direction only. Also I have heard that reamers will cut again if you twist them out (clockwise obviously) so its probably best top pass them through once and then tap them back with a soft mallet.

Starting to ream

Always worrying- swarf coming out mid way.

However the job was very successful so I cleaned up the reconditioned stub axles and swapped all the grease nipples for new.


The top trunnions were a little corroded inside and the new bushes would probably not fit like that. The trunnion  needed careful dressing internally with a half-moon file to remove the worst of this and restore the double conical profile.

inside profile restored

There was also some damage to the top surfaces of both trunnions and kingpins where they were probably levered with a screwdriver in the past. This damage would obviously prevent the shims/thrust washer assemblage from sitting flat so this damage too was carefully filed flat.

Screwdrivering damage to trunnion/thrust washer mating face

Damage filed flat

I will treat the trunnions with Jenolite to stabilise any rust and hopefully prevent more before repainting them. I'll put the hubs and refitting all of this in a separate post.

Progress?

Well I've been struggling on with the MGB. Spent a fortune on parts and its been like Christmas with all the packages arriving here. Still, here is a summary of progress to date:

Rear brakes and hub oil seals. I tackled these exactly as described in the Dr-Doolin.com excellent YouTube video. No pics here because he says it all and my experience differed only marginally as my car has alloy not wire wheels.

I found the brake shoes were virtually new both sides but the N/S rear hub seal was clearly leaking and as a result hub and shoes were very oily. I replaced the oil seal and shoes this side giving everything a good clean. I do have the parts for the O/S but as the shoes were new and seal not leaking I left these for the time being.

I had the exhaust (and the duff mountings) replaced with a new mild steel system (can't afford stainless at present). Vast improvement in both sound and exhaust fumes in the car.

I took my first tenuous steps in carburettor tuning. I had filthy black plugs and colortune confirmed its running really rich. New air filters surprisingly gave a vast improvement and mixture adjustment with filters on also gave a smoother (not smooth) idle.  Finally I attempted balancing, and things are definitely better! I will detail all these procedures later as I plan a carb rebuild anyway. One problem I have though is that when the motor is warm the idle doesn't return to normal but sticks around 2k. The motor will also increase in speed on its own!

Checking various forums shows similar problems are common... The most common cause being  a stuck cable. This isn't the cause in my case (and I'm not sure I believe it when it was identified in some if the documented cases either!). Anyway in my case the effect occurs even if I don't touch the pedal, and when it does both carb throttle levers are solid on their stops. Pressing here doesn't lower idle speed again and blipping the throttle, either by hand directly on the lever or at the pedal, doesn't help either. In order to slow them down the simplest way is to put a hand over the carb air intakes. I have also backed the fast idle screws right off and loosened the spindle clamp bolts as well as all cable connections and it still happens!! This all sounds like an air leak to me but I can't find one. Possibilities include a leaking gasket somewhere or maybe the poppet valves on the butterflies introduced in the Hif4 carb. I understand these are designed to admit air and prevent over-richness when the throttle is snapped shut. However they apparently can stick open  if their springs are weak (which may happen if they get hot). I understand now (too late) that replacing the butterflies with HS4 solid plates is considered preferable. I did seek advice from Burlen Fuels SU shop and was advised to stick to the originals... Seems not to be the best advice and perhaps driven more by the need to empty the stock room... Or maybe that's just my cynicism!! Anyway new valves can't hurt. I am planning a carb rebuild and I have the major rebuild kit and a few extra gaskets to refit everything in case of air leaks so I will describe this later.

I have installed a battery clamp and de-rusted the carrier... Both of which were pigs of jobs as access is really bad... My back may never be the same again! Still, at least replacing the clutch pedal return spring was easy.

I have also started to recondition the two spare stub axles I bought but that really does need a separate post!