Oil Pressure

[Ian Abel]

Hi All
The oil gauge on my 1998 Chimaera 4 will read at 30 generally when running but sometimes when idling will drop down to 5 or even zero. When I move off again it will generally go back to 30. It never goes over 30. The car is going in on Friday so would like to it sorted while in there, now is it the sender unit that's playing up? Assuming the gauge must be ok as does seem to work/move!!
Many thanks in advance.

[bobfather]

I think you haven't done your homework. These pages are full of this issue, it is very common. Yes the sdnder is always the problem, they have a limited life. There are lots of aftermarket options via ebay for £15 upwards or you can get one from TVR Parts for £70odd

[Discopotatoes]

If the yellow light didn't not come on then your oil pressure should be above 7psi, presuming it lights up and goes out on start up. I just bought one from merl in motorsports about £45

[Ian Abel]

Many thanks........ebay here I come

[bobfather]

This one will work

ebay oil pressure sender

[Ian Abel]

Is it worth getting the 2 stud sender as someone mentioned to me? Don't want to waste my money unless it is for a purpose

[bobfather]

Ian Abel said:

Is it worth getting the 2 stud sender as someone mentioned to me? Don't want to waste my money unless it is for a purpose

...and make sure the second stud is 'ground', sometimes the second stud is a pressure switch

[citizen smith]

When you turn the ignition on, where is the needle pointed. If it is below zero, then you will always have a Low Reading!

Possible Gauge error?

[Ian Abel]

Hi
No the gauge works, moves to 30 on start up. Just when sat in traffic it will drop to 5 or below. warning light doesn't come on. Does when ignition is switched on. I think the pressure is ok and read that its an TVR common problem so not really worried, engine drives fine and certainly oil level via dipstick is good. Just would be nice to maybe have a more accurate reading and seems like it is an easy fix that is neither hard or expensive to do.

[TJC46]

Ian Abel said:

Is it worth getting the 2 stud sender as someone mentioned to me? Don't want to waste my money unless it is for a purpose

One of the 2 terminals is an earth and it means more reliable readings.

If you think about it the TVR one is earthed by the senders screw in thread.

Most people, like i did myself, either use ptfe or thread sealer on the thread to stop tiny annoying oil drips and this makes for a poor earth connection.

[Discopotatoes]

Ian Abel said:

Hi
No the gauge works, moves to 30 on start up. Just when sat in traffic it will drop to 5 or below. warning light doesn't come on. Does when ignition is switched on. I think the pressure is ok and read that its an TVR common problem so not really worried, engine drives fine and certainly oil level via dipstick is good. Just would be nice to maybe have a more accurate reading and seems like it is an easy fix that is neither hard or expensive to do.

what grade of oil are you using?

[ClassicChimaera]

Ian Abel said:

Hi
No the gauge works, moves to 30 on start up. Just when sat in traffic it will drop to 5 or below. warning light doesn't come on. Does when ignition is switched on. I think the pressure is ok and read that its an TVR common problem so not really worried, engine drives fine and certainly oil level via dipstick is good. Just would be nice to maybe have a more accurate reading and seems like it is an easy fix that is neither hard or expensive to do.

If you replace like for like you'll likely find it will read similar to the one you've just removed.
What year is your car and do you have the later gauges fitted.
Mines a 2000 car and displayes the same readings as yours.
You'd be surprised how accurate it is at low revs. Mine does not go above 30 psi but the engines running at 45-50 psi.
On tickover it often reads 5 or even lower if hot.
Its reading slightly low because with a mechanical gauge my car on tickover hot reads and 10-12 psi instantly rising to 20+ from 1200 revs upwards.

I've fitted an Isspro sender with the separate ground. It reads 10-15psi with just the ign on. It's not suitable for cars with the later curberant ( spelling?) gauges with the silver bezels.
It reads 45 on tickover and 60 from anything from 1500 revs, looks good but is fiction!

[bobfather]

I understand the reasoning behind grounding (earthing) and ptfe but the reality is that ptfe sealing of a tapered thread will always result in adequate grounding. ptfe is a very soft and delicate material that cuts easily at the thread peeks

[Discopotatoes]

bobfather said:

I understand the reasoning behind grounding (earthing) and ptfe but the reality is that ptfe sealing of a tapered thread will always result in adequate grounding. ptfe is a very soft and delicate material that cuts easily at the thread peeks

or just put a copper washer on over the threads to seal the body

[Ian Abel]

I get it serviced at Neil Garners so guess the oil is correct, haven't the paperwork in front of me at the mo. It is a 98 T reg with the later chrome bezel surround gauge.

[Discopotatoes]

Ian Abel said:

I get it serviced at Neil Garners so guess the oil is correct, haven't the paperwork in front of me at the mo. It is a 98 T reg with the later chrome bezel surround gauge.

worth ringing and asking as different specialists have different preferences, some like 10w 40 some 15w 50 the engine was originally run on 20w 50 so if yours is getting a bit leggy it might be worth going slightly thicker, I've used 20w 50 and 10w 60 got better pressures with the latter,

[bobfather]

Discopotatoes said:

or just put a copper washer on over the threads to seal the body

Copper washer definitely the way to go for parallel thread but these 1/8npt are normally tapered it therefore shouldn't be possible to screw it in to the shoulder

[Discopotatoes]

bobfather said:

Discopotatoes said:

or just put a copper washer on over the threads to seal the body

Copper washer definitely the way to go for parallel thread but these 1/8npt are normally tapered it therefore shouldn't be possible to screw it in to the shoulder

fair one.
found this interesting under NPT about sealing threads
https://www.valvesonline.com.au/references/threads...

[Sardonicus]

Is a tapered thread no need for any sealers of any kind if you want to use something like Loctite 577 then that your choice and fine

[Ian Abel]

So which is the best sender to use:
Original - but will get similar readings to the one I already have....and costly
Single terminal one - cheapest
Twin terminal one - use separate earth

Which would give me the most accurate readings?

ps- does the oil escape when changing the sender, assume it does.