Hot steering

[mhag]

When the engine bay has been at full temp for 10 mins the steering on my 500 gradually becomes slightly heavy and the caster return goes completely. I can take my hands off the wheel on a roundabout at 30 & keep going round. Cool off & it's light & snappy again.
It feels just like my S2 with seized UJs, but I've had these replaced.
Also replaced PAS fluid, PAS pump & the geometry has been done.
Had the shocks replaced with Nitrons which transformed the handling but not the steering.

What next?

[jesfirth]

stumped - worn rack?

[bluezeeland]

Top and /or bottom ball joints ?

[mhag]

Still a problem...it only comes in when the engine bay is at full temp for 10-20 mins. It's not disastrous but the car loses feedback and has to be "actively" steered out of corners, a bit like driving a power boat.
3 garages have had a look including a TVR specialist.
So far I've:

replaced UJs
replaced PAS pump
Nitron suspension
full geometry & wheel alignment
refurbished the PAS rack

Not much left...could the UJs be jamming as the central shaft heats up next to the exhaust? I have little practical experience so I'm entirely beholden to the advice of the mechanics & it's not working out well for me!

[bluezeeland]

Has someone actually checked free movement and play/seizure in the top and bottom ball-joints of the uprights ?

[mhag]

PAS rack disconnected then engine run to full temp, steering column apparently fine without the rack.

[The Red Baron]

Check the universal joints on the steering column?!

I had one this year that was practically seized, although all the time, not just when the car was hot.

[jesfirth]

just a though - do you by any chance have an electric power steering pump like mine rather than the mechanical one. If so could it be over heating?

[77racing]

jesfirth said:

just a though - do you by any chance have an electric power steering pump like mine rather than the mechanical one. If so could it be over heating?

Hi Man,
Hope you had a good season ? Electric power steering ECU has a thermal heat switch built in. When it gets hot it just stops working ie no assist. I chased that problem for over a year on my car. Turned out to be exhaust manifold heat wash. Moved ECU from where it was on bulk head and put a cold air supply to it job done

[mhag]

Many thanks for the suggestions. I'm planning to go to Thornfalcon Classic with TVRCC on Sunday, so may be someone there will have further ideas. Then it's back on the ramp next week. I've spent the best part of £3k chasing this & it'll probably turn out to be a worn/seized joint...Saw me coming?
I'll ask about the uprights, although 2 garages have dismantled the steering, & TVRSSW took the suspension apart earlier in the year. New mechanical pump.
BTW left my copy of the Heath Bible with the garage, then I saw this:
https://www.amazon.co.uk/TVR-Griffith-Chimaera-Ste...
Really?
2nd edition still for sale at ECUmate at a normal price

[mhag]

Update: finally got it sorted last Nov, thanks, TVRSSW! Not much chance to drive until now.
Turned out to be a combination of factors:

PAS rack failed
PAS pipe had been re-routed during a rebuild too close to the exhaust so the PAS fluid was red hot.
Driver side upright stiff
Replacement UJ had a notch (the original UJs were probably OK)
Refurbished PAS rack too tight

Most of the cost was labour, dismantling the entire front end & going over ever component one at a time. Because the problem was only apparent when the engine bay was at full temp even Col at TVRSSW thought it was figment of my imagination.
Until the car tried to drive him into the side of a truck on the M5...
All good now.