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MG MGB GT V8 Factory Originals Technical - How to fit a temp gauge

I have a 95 4.2L Rover V8 with hot wire efi. I recently bought one of those nice dual gauges, half oil pressure, half water temp. The water temp is mechanical and the Rover engine is designed for an electrical water temp gauge. Any ideas how I can fit the mechanical water temp gauge?
Regards
Tony
Tony Bates

I just fit one of those gauges yesterday, the way it is set up on my factory intake manifold is that the bulb for the water temp screws into a port on the front of the manifold on the left side, looking into the engine bay from the front. I did need to get a small adapter from Bromsgrove in the UK to get the bulb to fit, but it all went together nicely. If you need a picture, let me know.
Jake

Hi Jake,
Thanks for the input. My intake is the hot wire fuel injection one and and it doesn't appear to have a port big enough for the temp gauge bulb. Hence my question.
Regards
Tony
Tony Bates

Something creative in the recirculation/heater line?
Peter




I had the same problem with the bulb on a water gauge a while ago, radiator was only place that a hole big enough to fit it could be sited, took another direction, the thread on the bulb was identical to the sump drain plug, now got a very cheap,easy to fit oil temp gauge.




























































Russell

Tony - if your rig is Rover FI - the hot water outlet on the starboard side of the inlet manifold is removable and will take the 'bulb' sensor with a very ordinary plumbing sleeve in 'imperial' thread (can't remember the sizes). Alternatively the outlet beside the thermostat is another possibility although this might displace the fan temp sensor.
Roger

Hi Roger,
Yes it is the Rover Hot wire and manifold. When you say the starboard side, do you mean the side with the oil pump? If so, which outlet do you mean, there is an outlet to the heater, is that the one? The standard electrical temp sensor is on the left side (looking from the drivers seat forwards)next to the coolant temp sensor for the EFI and it looks like it's M10 or 3/8". Would it be OK to remove the AC fan switch in the thermostat housing and fit the temp bulb there? If so, what's the size of the thread for the switch and will the gauge read OK being that side of the thermostat rather than the engine side?
Regards
Tony
Tony Bates

Tony

If your inlet manifold is a later model one like mine it wont have an outlet on the front "starboard" (right) side. If its like mine, there is an outlet for the heater on the left and another for the bypass pipe on the front left. Plus there is the small outlet for the standard Rover electric temp sender on the left beside the EFI temp sensor. You really want to fit the sensor on the manifold as fitting it on the thermostat housing will not give you engine temperature while the thermostat is shut.

I solved the problem by getting a boss for the MG sensor welded onto the front left side of the manifold

Geoff
Geoff Richmond

Hi Geoff at al,
Yes your manifold sounds like mine, with the small temp sensor next to the collant temp sensor for the EFI. You say you had a boss welded onto the front left side, can you expand on this?
Regards
Tony
Tony Bates

Tony,
My '94 manifold had a hole on the front port side of the manifold below the thermostat housing. This is the recirculation out let for '85 to early '90's motors and when Rover went to recirculate through the heater valve they just blanked it off with a bolt. I "reactivated" it as I'm using the RV8/'80's front.
Either there is a largish bolt there that you can undo, and use the hole for your thermostat, you might need to use some plumbing fittings to reduce the hole, then drill and re-tap the inside of the brass fitting. Or possibly drill and tap a hole in centre of the "bolt". Or better, if there isn't anything there you can drill and tap your own hole/thread as it is a handy flat surface. You would need to remove the distributor to get free access to the "bolt"

I attached my MG heater valve to the hot water outlet on the top RHS of the manifold, but if you're not using that, Roger's quite right, that's more accessable.
Peter

Tony - it sounds as if there are almost as many variations as they made cars - however, back to first principles; your inlet manifold will have two or three 1/2inch plus outlets - the thermostat housing should contain a threaded aperture for the cooling fan heat switch - most us keep this simple uncomplicated way of switching on the fans but in some of the EFI systems, the ECU will switch the fans on - which means you could ditch the OE heat switch and fit the guage sensor instead, alternatively there is at least one other - possibly two water outlets from the manifold -one which will be needed for the heater - the point I was making earlier was the outlet(s) which have a rounded stub in order to receive a rubber hose -the stubs are screwed into the manifold on a 1/2 or 5/8 thread - and all good plumbers will have sleeves to reduce all the standard measurements.

Geoff is correct in saying that the measurement really ought to come from the hot side of the thermostat - significantly the OE fan heat switch was fitted on the cold side.

Finally - If my memory serves me correct - the later RB cars had an electric temperature guage - the same size as the dual guage - the RV8 dispensed with a pressure guage altogether on the basis that the Rover/Buick lubrication is almost a freefall rather than high pressure system and all a pressure guage would achieve would be to worry drivers unnecesarily about their incredibly low oil pressure. Tony what I am saying is - if all the plumbing is too difficult, you could use an electric guage for water temp and a warning light for oil - you will always get your money back on a dual guage !
Roger

Thanks all,
Peter - yes, my manifold also has the recirculation outlet on the manifold, blocked by a bolt. As I am using a buick water pump and also fitting A/C, I assume I will have to use that port for recirculation as it won't go via the heater (because of the A/C). My heater outlet port is from the starboard side outlet, like yours and Roger.

Roger - per your suggestion, I will be using the cooling switch in the thermostat housing to switch the cooling fans on. I specifically bought the gauge for the period look, but it may just be too hard.

Would the gauge work OK if I fabricated a Tee piece to go in either the heater outlet or the recirculation outlet that would allow the correct water flow and the insertion of the temp bulb? The only other options I see is an electric gauge or drilling out the original sender location and retapping or welding on a bung for the new bulb?
Thanks
Tony
Tony Bates

Hi guys,
Another question, am I right in assumimg that I need to re-use the recirculation port as the water will not be flowing through the heater when it is turned off? Is there some other plumbing solution to providing water flow during the period before the thermostat opens?
Regards
Tony
Tony Bates

Tony

I welded a threaded boss (or bung) onto the inlet manifold on the flat face of the manifold just to the left of the thermostat and below where the EFI temp sender fits.

Another plumbing solution I have seen (on a photo of Roger Parker's car) is as follows: There is a quarter inch pipe exiting the manifold near the middle of the left side. On my car it is connected to a six inch hose with a blanked off end. Dont know what it is for but assume it either does nothing or can be used for bleading out air when refilling the cooling system. On Roger's car he has connecteda hose to tee this into the hose between radiator and rad expansion tank. I believe that this will act as the thermostat bypass plumbing. I understand that Roger has simply blanked off the bypass outlet on the front left of the inlet manifold. If you went with this arrangement you could fit the temp sender into the bypass outlet (presumably with a suitable adapter).

Regards Geoff
Geoff Richmond

Hi Geoff,
My understanding is that the 6" pipe you refer to is probably the water feed to heat the plenum chanber. I also understand that it is often not used so Roger's idea of maybe using it for the thermostat bypass is a great one. I could then leave the port below the thermostat housing for the temp sender.
Regards
tony
Tony Bates

Tony,
You defintly need some sort of recirculation while the engine warms and until the thermostat opens, otherwise you're going to get hot spots and other weird effects I imagine. I don't know what front you're using, I'm using the RV8 /late RRover '80s one which has a recirculation port on the pump as well as the heater return line port. The later Range rovers (different front cover) used a dual valve on the heater line so that it would bypass the heater and recirculate when "off". The one I got (and didn't use) on the '94 motor operated by a vacuum line, but I've seen cable operated versions on a variety of modern cars (ie my old '84 subaru) .
Roger , interesting to hear about the computer controlling the fans. Mines a 1994 (possibly '95) computer and it sounds a possibility worth investigating.
Peter

The factory V8 has a small-bore hose from a pipe on the left of the inlet manifold to one on the thermostat housing i.e. bypassing the thermostat. If this gets blocked the temp gauge goes berserk, while warming up I have seen it point to 40psi on the oil gauge! Many conversions don't seem to have these, and one I drove showed similar but not so dramatic fluctuations unless the heater valve was open a tad. The factory V8 also has a 1/2" bore bypass pipe inside the manifold with its open end by the heater valve and the other end with a hose to the water pump, along with another hose from the heater return (its pipe being undeneath the inlet manifold). The internal bypass also became blocked on my V8 which seems to have been one of the causes of the cooling system pumping up with air and blowing coolant out of the expansion tank overflow. Whilst the gauge then did not show the same fluctuations as before, it is definitely lower and more stable during warm-up now.
Paul Hunt

Hi Paul,
I assume the small bore hose from the left side is the one used for the plenum heater on EFI models. I have the buick/SD1 style from cover and pump. The heater return goes into the inlet to the pump and there is another inlet on the back of the pump/timing cover that usually coonect via a shrt (<6") hose to the base of the manifold, below the thermostat, that acts as the bypass. My challenge is where to plumb the water temp gauge into.
Regards
Tony
Tony Bates

This thread was discussed between 10/11/2003 and 19/11/2003

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