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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin Sportster, Cabrio, Berlinetta and Roadster builds

Marlin Sportster, Cabrio, Berlinetta and Roadster builds Enthused or Confused about your vintage Marlin build? Ask away here or show off your build.

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  #61  
Old 25th April 2016, 19:59
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MartinClan MartinClan is offline
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The fact you have some voltage albeit low means it has to be a poor connection. Have you checked the starter solenoid? Normally this also behavesas a relay switching tge feed to the starter.

Robin
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  #62  
Old 25th April 2016, 20:59
NigelB NigelB is offline
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Ian,
I learnt an interesting trick from an RAC man one day. If you hear the click of the solenoid, but the starter doesn't turn, then turn the key and whack the starter with a hammer at the same time (via a long drift if your starter is as inaccessible as mine and it probably needs two of you). If the starter then turns it's likely the starter is on its last legs.

I had a random failure of the starter on my Sportster. But it worked when I whacked it. I changed the starter and have had no problem since. I didn't measure any voltages though so can't comment on the numbers you get.

And now I've just read your original post on this and maybe it sounds a bit more complex than a simple starter problem. But it's probably worth trying to eliminate it if you can.
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  #63  
Old 26th April 2016, 21:07
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Quote:
Originally Posted by MartinClan View Post
The fact you have some voltage albeit low means it has to be a poor connection. Have you checked the starter solenoid? Normally this also behaves as a relay switching the feed to the starter.

Robin
I agree.
Have you checked the battery ground connection to the chassis and the engine ground strap?
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  #64  
Old 28th April 2016, 17:20
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I think you're all right about the bad connection. On Sunday I thought that I'd cured the problem by tightening the starter motor cable post as it seemed a little loose. I assumed that the heat from the engine had worked it free. But when I hit the same problem a few hours later it was fiddling with the positive terminal on the battery that did the trick.

My battery posts, rather than the soft lead ones you get on normal batteries are solid brass screw in ones that taper slightly. As far as I can tell the clamps on the cables are not tapered so I'm wondering if this is enough for them to work loose. If you test the voltage near the battery but not on the terminals it still reads 12.8V but maybe the surge of power for the starter is enough to dislodge it. You can slowly turn the clamps on the posts which doesn't bode well. I may screw the B+ cable direct to the battery using a ring terminal rather a clamp and see if that improves things.

I'm really hoping that the loose connection is not on the terminals under the scuttle as that will mean an annoying amount of dismantling. I'm starting to regret burying so much of the electrics in inaccessible places.
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  #65  
Old 28th April 2016, 19:46
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Battery connection sounds ok but the way to test it is to put the meter on it when cranking the engine. Then you can see if there is a significant voltage drop. As V = IR when cranking you will be drawing 100's of amps. Evdn a resistance of 0.05 ohm will produce a significant voltage drop.

Robin
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  #66  
Old 30th April 2016, 19:01
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I may have found the culprit. The fuse-able link I'd installed showed signs of arcing on the back of the ring terminal which indicates it was not making a good enough contact for the current surge when starting the engine but may have been ok for low power stuff and charging the battery. I've removed the link and bolted the two ends of the cable together. The engine has had a few successful starts with no issues seen so I'm hoping that's the problem solved. Only time and testing will tell though.

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  #67  
Old 2nd May 2016, 15:40
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I'm pretty certain my starting issue is now solved. It's fired up over 10 times now hot and cold without a hitch. Thanks for the pointers, saves me wiring a separate ignition switch (was my next port of call).

I've just got the cooling issue to sort out now. I pulled out my temp sensor and instrument panel and bench tested it at a range of voltages between 12 and 14V. The gauge its pretty accurate; the resistance of the sensor looks nothing like the VDO literature but it works. At 14V it reads correctly all the way down to 70 degrees. I went out for a drive this afternoon and the engine was hovering around 95-100 depending on whether I was driving hard or coasting. When I got back I put my hand on the radiator top hose to find it scorching and very firm to the touch. The Rad top tank was painful to touch (and was leaking a little coolant under pressure from the cap seal). The bottom hose was at the ambient temp of the engine bay and the rad bottom tank was positively chilly. The rad didn't feel at all warm until halfway up and was only getting hot in the upper third/quarter. So it looks pretty conclusive that either the thermostat is not opening or the rad is well and truly blocked, which is pretty unlikely.

I'm just amazed that it hasn't over heated more. The DME must have been jumping in and helping with timing etc. Fixing this may therefore have a positive effect on performance too.

I've ordered a new 92C and 87C thermostat to experiment plus I'm going down to Marlin on Friday to get the louvres cut in the bonnets. Hopefully my cooling woes will soon be over
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  #68  
Old 2nd May 2016, 19:34
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I think as a first test I would just remove the thermostat and see what difference tgat makes to the rad temp.

Robin
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  #69  
Old 2nd May 2016, 20:32
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I've just finished ripping the thermostat out and testing it in a pan on the stove. It opens nice and wide...at 98 degrees! That explains a lot. It then slowly starts to close around 97 degrees to 88 degrees though this is without the spring on the back pushing on the block so it would probably close up around 95 in the car. I had to hold a lid down on the pan to build up pressure with steam and scalding water spitting everywhere just to get it to reliably open at all.

It has no markings on it indicating the operating temperature. Obviously a mistake or a dodgy part. I seem to remember when I bought it as a kit with the housing and seals, they forgot to actually include the 'stat and sent it on later. Probably just grabbed one randomly off the shelf.
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  #70  
Old 8th May 2016, 13:37
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Rebuilt the cooling system with the 88 degree thermostat yesterday and the car is holding ~91 degrees nicely now. I did the little trick of drilling a 4mm hole in the top of the thermostat outer ring to make filling and bleeding the system easier too. The last piece of the puzzle is to swap out the fan switch. My current one is mounted in the top tank and set for 92 on / 82 off so it triggers too early and then never switches off. If mounted in the bottom tank this wouldn't be an issue. Rather than go to the hassle of getting the rad modified, I've ordered a new switch from a Peugeot 405 which has 97-92 and 101-96 settings. This way I should be able to ensure that the fan comes on only if the rad is struggling rather than the engine just running at the normal temp.

My under bonnet (and my feet) temps don't seem to have gone down much since getting the bonnet louvres cut but this will come in to play more on really hot days.

Last edited by morris; 8th May 2016 at 13:41..
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  #71  
Old 12th June 2016, 11:19
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Just a bit of an update on the Sportster running in period. I've now covered over 500 miles and things seemed to be going well... until this week, when I had two separate breakdowns.

The first related to the copper coolant pipe that runs from my header tank to the back of the water pump. The front end of the pipe has no bead on it but is just held in with a jubilee clip. This proved not to be good enough and it popped out last Sunday when I was about 6 miles from home on the start of an outing as the weather was so good. I noticed my temps hitting 110 so pulled over and found coolant all over the side of the block. I had no tools with me so unfortunately had to call the RAC as I couldn't even get the side panel off the bonnet. Fortunately the incident happened half a mile past a pub so I limped the car back there, call the the RAC and settled down with a pint in the sun for an hour and a half wait. It took 10 minutes to get the hose back on so I just need to look for a more reliable fix long term.

The second breakdown happened just 4 days later on Thursday evening when I was out road testing the car after draining the tap water out and refilling with coolant. I was about 4 miles from home after a good 25 mile loop, went to pull out at a junction and couldn't find any gears. I coasted into a bus stop and realised that the gear linkage had come off somewhere. I initially thought it was the bush at the rear as I could move the stick up and down quite freely. This was not the kind of thing that was going to be fixable on the side of the road given the linkage is buried above the exhaust and the propshaft and I was loath to call the RAC twice in 4 days. I managed to force the car into gear using one hand to fix the base of the stick and luckily it turned out I'd found 4th. Given the car is so light, I was able to rev the engine, slip the clutch and pull away just trying to avoid coming to a complete stop where possible. When I got the car up on stands yesterday it turned out to but the front of the gear stick carrier arm had come away from the top of the box. The pin that held it in place was completely missing. An M8 bolt and a nyloc soon sorted that out and the car now changes gear smoother than ever.

One of the things I really need to prioritise is the suspension settings. Although it handles great on a good smooth road, as soon as you get any undulations on less maintained B roads, the back end grounds out with a spine shattering jolt and steering and back end get very skittish.

I also invested in a GoPro camera that I've mounted on the top of the roll over bar using a pair of exhaust clamps. I always promised myself I'd buy one once the car was finished. The built in mic was useless as all you got over 20mph was wind noise so I've been playing with two external mics placed in different places around the car. One under the bonnet next to the scuttle and one inside the boot seems to give the best result so far

https://www.youtube.com/channel/UCaE...iLeKrQwmLUrdwQ

Last edited by morris; 12th June 2016 at 11:21..
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  #72  
Old 12th June 2016, 13:49
phil.coyle phil.coyle is offline
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Quick fix for the copper coolant pipe is to solder a compression olive onto it, or sacrifice a compression fitting by tightening it up on the end of your pipe and then remove it and carefully cut off the nut left on the pipe.
Left with one swaged end you can force the rubber pipe over and fasten with a hoseclip.
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  #73  
Old 12th June 2016, 13:54
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That's a good idea. I was thinking of soldering half a straight joiner but that would make the pipe a little too large on the OD for my hose. The olive sounds like the best plan.
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  #74  
Old 12th June 2016, 14:27
phil.coyle phil.coyle is offline
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I had a similar experience to you with a 8 mm pipe sliding off, and after searching around the garage found an old pipe with an olive attached, and therefore no more problems and that was 15 years ago.
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  #75  
Old 12th June 2016, 17:27
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I whizzed down to screwfix this afternoon and picked up a bag of 22mm olives and soldered one on each end of the pipe. I was worried that I was going to have real trouble getting the tight silicone hoses over the ends but I found a tube of silicone grease in my tool chest and with that smeared on, they went in no problem.

Fingers crossed that will be the last of this particular issue (and any others for a while)
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  #76  
Old 12th June 2016, 22:24
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Quote:
Originally Posted by morris View Post
the things I really need to prioritise is the suspension settings. Although it handles great on a good smooth road, as soon as you get any undulations on less maintained B roads, the back end grounds out with a spine shattering jolt and steering and back end get very skittish.

[/URL]
Hi Ian
I had the same problem with my back end bottoming out. I took out the 'top hat' rear ride height adjuster and took about 30mm off the skirt. I then replaced my 6" springs with 7", refitted the adjusters, backed them right off and have never bottomed out since. It was a bit of a pain to do but certainly solved the problem.

Nigel
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  #77  
Old 13th June 2016, 17:27
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Nigel, yep, that was my next plan. 30mm? I think mine are only ~40mm in length anyway. Were yours extra long or were you left with just a coil's worth of material? I suppose the 7" springs let you raise the adjustable part of the spring seat further up the thread and still achieve the same overall ride height. I'll try trimming the top hats first before investing in new springs though. I had wondered if it was actually the springs binding rather than the top hats touching as looking at them there appears to be no marks or damage
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  #78  
Old 13th June 2016, 18:34
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Ian,
I had more than a coils worth of skirt remaining. Perhaps it wasn't quite 30mm. But I remember that I had to drop the front of the trailing arm to get sufficient movement on the lower wishbone to get the 7" springs in so now, even at full downward travel of the rear suspension, the coils are under slight compression.
Interesting comment about there being no witness marks on the skirts. Mine were the same. Probably the only bit of decent powder coating on the whole car.

Nigel
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  #79  
Old 19th June 2016, 12:03
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Nigel,

I've taken some photos of my springs and think i can see the issue. The first is with the car off the ground and the spring at its fullest extension. you can see the damage on the coil's powder coat so the springs must be binding together. There's no feasible way for the mounts ever to come in contact (hence lack of damage)



With the car back on the ground you can see the coils are very close so it's inevitable that they will come into contact.



So I have to decide whether to go with longer springs as you did or just go for a higher spring rate. The current ones are 400lb. I seem to remember you saying you tried 600lb and they were too hard? maybe 500lb with 7" would be the compromise as I actually find the back end too soft ( I lift out of my seat going over cattle grids fast, which bearing in mind I weigh over 17 stone...)
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  #80  
Old 21st June 2016, 20:58
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Quote:
Originally Posted by morris View Post

So I have to decide whether to go with longer springs as you did or just go for a higher spring rate. The current ones are 400lb. I seem to remember you saying you tried 600lb and they were too hard? maybe 500lb with 7" would be the compromise as I actually find the back end too soft ( I lift out of my seat going over cattle grids fast, which bearing in mind I weigh over 17 stone...)
Ian,
I've never tried anything more than 400lbs and I've settled on 400lbs 7" springs. They are a good compromise between comfort and stability and I'm only a couple of stone lighter (at least I was when I last weighed myself 3 or 4 years ago..........!!) than you.

If you're bouncing out your seat is there anything you can do with your shocks??
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