Hot engine

[philipdawsonladds]

I have just managed to fail my IVA with an Aristocat and wonder if anyone else has had a similar issue?

I have an XJ6 Series III 4.2 engine which I have fitted to a 4 speed Manual OD Moss box from an early S type. The only mod that I made was to extend the slave cylinder piston to make the gear change easier (using a long bolt with the end rounded off).

With the engine cold and battery charged the car starts fine, gears are engaged easily and the car drives well After 2-3 hours of testing at the station the starter became progressively sluggish (even with a fully charged battery switched over or using jumper leads) and then I couldn’t engage any gear (hence no speedo test). I got the car home and after a cool trip on the trailer retried – everything worked fine! Clearly something to do with the engine getting hot. Any ideas or suggestions on where to look?

I'm thinking overheating as the car was just in the test station on ramps etc., with the engine running - water temp was normal though. Or maybe the clutch piston is of the wrong metai and is expanding too much?

Any creative ideas welcome - I have rebooked the test and will get the speedo checked out first!

[Tintin]

I would suggest looking at the starter motor itself and associated wiring - engine heat may be causing an increase in electrical resistance leading to poor current flow.

As to the clutch, I would be looking at the hydraulic hoses - heat may be weakening the rubber causing the hose structure to "balloon" under pressure from the pedal.

I can't immediately see a connection between the slow starter motor and gearbox engagement.

Robbie

[philipdawsonladds]

Thanks - I am going to double check/replace the earthing to the starter (which has just been refurbished) - the hydraulic hose does have a little twist in it so could be an issue - it was very fiddly to fit with the slave cylinder in place so I might reconnect (new one) to the slave before bolting that to the bellhousing. I appreciate the thoughts! In replacing (extending) the push rod from the slave I might not have left any gap which might also be an issue. Nice cold day so a little time in the garage perhaps!

[NATONEIL]

I agree with Tintin that a good check of the main earth and all connections to the starter are needed, but I am surprised that you are suffering from overheating during the test. I presume this is a good engine and cooling system and the thermostat is working correctly. If you have an electric fan check that the operating temperature range for the switch is suitable.
As far as the clutch goes please let us know what you find. I have a similar problem and cannot cleanly select reverse with the car stopped and the engine hot. My car is a Suffolk SS100

PS why did you go for the Moss Box? I would have thought the standard XJ6 series 4 speed with OD would have been better.

[philipdawsonladds]

Well it was a new thermostat so that should be OK - fan belt a little loose (maybe an issue) - engine was a recon unit with excellent pressure on test - if I could have found a manual XJ6 box I would have used it but they seem like hens teeth. I am thinking earthing is one issue - the slave cylinder piston (which I made from a long bolt) may not have the correct clearance - should be 3/4" mine is probably zero! I'll let you know how I get on - as it's pouring with rain I might get to the garage now!!

[Tintin]

fan belt a little loose (maybe an issue)

If you are running with a viscous fan coupling check that the pulley is turning the fan blades at a satisfactory rpm - the viscous units can fail and are often overlooked as a cause of overheating when the car is not moving forward through the air (no ram effect cooling).

Robbie

[NATONEIL]

Phillip

You have probably sorted the problems but my car started to show similar clutch / gearbox issues this summer. The longer I drove the harder it became to get the clutch to disengage. Yet next morning it was fine. I discovered that the inside of the clutch flexible pipe had failed and was acting as a non return valve and had worn the thrust bearing out. If you are still having problems then I would look at the flexible.