Cool V8?

flatcat

New Member
I finally took the plunge and bought a P6 3500 recently, a car that I've admired for some time but somehow always avoided buying. Anyway, I've got one now and apart from the creeping feeling that it isn't quite as good as I thought it was (sounds familiar?) I find that I quite like it.

One of the problems I noticed almost immediately was that it didn't warm up properly - even after a considerable run, the engine temperature resolutely stayed at the right edge of the 'white' part of the temperature gauge. The oil pressure seem to confirm this - even when the engine is warmish, it doesn't go below 30 psi at idle.

JR Wadhams kindly plonked a rather large parcel on my doorstep on Friday, which contained a service kit and a new thermostat. After a bit of swearing the radiator was drained and the old thermostat removed. Bingo! - or so I thought, the old thermostat was stuck slightly open. Out comes the old one, in goes the new one, a mental note about the amount of crud in the cooling system is made and all goes back together.

Unfortunately it's still running cold, the oil pressure is still rather mental and I'm wondering if I missed the bleeding obvious as I'm not that familiar with the car. Although I'm getting the felling that this will change soonish.

I know that the car badly needs a service, which will happen next weekend, but I'm not sure that it'll make a big difference. Given the amount of crud in the cooling system it should rather run hot than cold.
For the record, the car is an early '72 3500 Auto with 2 previous owners and most likely genuine 31k on the clock.
 
Flatcat,
It's very unlikely that your car is actually running cold - Most likely the sender / gauge is not working properly.
To check, remove the wire from the sender and touch a good earth (like the engine) with the ignition on. The gauge should travel full scale, into the red. This shows that the gauge is working. (Maybe the sender is not working?) With the engine at running temperature the top hose should feel hot. This shows that the thermostat has opened.
If cooling system is full of crud, try the old reverse flush to clean it out. Let us know how you get on.
Regards, John.
 
I checked the sender in the way john described i.e. using a good earth. this proves the wiring and guage.

If this doesn't work I'd put a test light on the end of the wire and connect to a good earth as if the guage is faulty it wouldn't move but the light should light up.

To check the sender you can use a multi-meter to measure the resistance, This can be done by putting one probe on the brass nut of the sender and the other on the spade conector where the wire goes, there should be a reading, if it is goosed then there is no change. you could also use a test light and a battery as above. if the sender is goosed then the bulb wont light up. Can be done with out removing the sender.

If the sender is ok then check the guage. Use similar methods using the mutli meter.

The oil guage problem can be checked in the same way.

I use a 9v square battery and a length of wire to check thing like the guage it is easier than lugging a 12v car battery in your tool box.

Have you checked the spade connectors for dirt etc. take them off and give them a clean. could save you some grief.

Another thing to be weary of since you mention the crud in the system is there enough coolant in the system. If there is not enough water in the system then the guage has nothing to read if you know what I mean. feel the pipes around the engine is there any that are cooler? is the heater hot?

Don't worry about it going wrong a few minutes under the bonnet will put your mind at rest.

I you are not brave enough to try it yourself contact the local co-ordinator I am sure he will help you out.
 
Guys,
thanks for the suggestions. A few points:
Both the gauge and the sender unit appear to be working, at least partially. I'll check earthing the cable to verify that/if the gauge is working as expected.

The top hose heats up as expected after a while, so the new thermostat is opening eventually. I was able to confirm this by peering into the radiator - coolant starts circulating through it once the the engine is warm, but not before and the flow changes depending on temperature.

The heater is kind of working, I'm getting some warm air with the lever set to hot but nothing spectacular. I hope that this just indicates that it needs a good flush and they aren't like that, because if they are I'm in trouble with the better half.

This might actually sound a bit stupid, but it appears that there are two coolant temperature sender units? There's one held in with three bolts just aft the thermostat housing, held in with three bolts, and another one at the front of the inlet manifold to the left of the water pump. Which one would be the correct one?

As to the oil pressure - I'll guess I'll change the oil, then flush the system and see what it's like afterwards. I suspect that the oil change is well overdue (car has only done a few hundred miles for the past five or six years) so it might simply be more crud in the engine. Just out of interest - what are the 'usual' oil pressures on a healthy engine when warm? The gauge indicates about 30psi at idle and about 50 when running at about 2500rpm, both when hot.

Yes, I know that I need to get a Haynes BoL - a mate supposedly mailed me one but it hasn't turned up yet.

Thanks for your help,
FC
 
Hi Flatcat

The P6 has a second Temp sender unit for the choke warning light. The warning light is more sophisticated than most, in that it come's on once the engine has warmed up, hence the extra sender unit. I believe its the one on the top of the manifold.

Oil pressure should be about 30psi when warm and running, ie when driving about. My P6 at idle gives about 30psi when cold and about 10ish when hot (with 20/50 oil). Of course as everyone says, 30 year old gauges probably wont be spot on and should be taken with a pinch of salt, not Gospel.

Hope this helps
 
Hi

If the sender is defective (mine was also reading cool) it is easy enough to pop into a local motor factors to obtain a replacement, (seemingly a bog standard part) its the one above the water pump, the one on top of the mainfold is the choke sender unit.

I had cooling problems earlier this summer (loss of coolant) and the amount of crud that I removed from the system was unbelievable - a simple flush is not enough, components need to be removed and properly cleaned, especially the heater matrix - I cleaned mine and the heat output is unbelievable - in all the P6's I've owned the heaters have never been that good, but having cleaned the matrix I can confirm that the performance should be good.

Good luck

Gary
 
Thanks all,
I checked yesterday evening and it appears that the sender is indeed the culprit as the temperature gauge was going all the way into the red when I shorted the cable against the engine block. That's good, because that's an easy fix...

Gary, how easy is it to remove the heater? It looks like it would benefit from a proper clean but I would prefer not to have to disassemble the whole car to get at it...

Cheers,
FC
 
Hi,

being a newbie I got a question. My thermostat seldom reaches 85 - only in midsummer's traffic jams. But it hits green after a short time. So I did the transmitter test but nothing happened on the dashboard. I had ignition on.

Did I miss anything?

Thanks a lot

Thomas
 
Thought so. There is a Otter switch right behind the thermostat. But maybe this is something else

Thomas
 
thob said:
Thought so. There is a Otter switch right behind the thermostat. But maybe this is something else

Thomas

Hi Thomas,

See rumblin_ron's post above:

"Hi Flatcat

The P6 has a second Temp sender unit for the choke warning light. The warning light is more sophisticated than most, in that it come's on once the engine has warmed up, hence the extra sender unit. I believe its the one on the top of the manifold."

Ron's quite right..it is the sender (made by Otter) secured by 3 screws on top of the manifold.

The dash temperature gauge picks up from the horizontal screw-in transmitter at the front of the manifold.

Cheers,
 
Hi flatcat,

Congratulations on the purchase!
With 31k miles probable, isn't there a chance that you've found yourself a nice tight V8 that actually has great oil pressure? Maybe reading 5psi over? A new sender (although fiddly to get at) could tell you otherwise, or a garage that has a tester? Mine has maybe 30k kms on it since it was rebuilt, gives 25 psi idle and 40+ on the road warm.

The heater unit comes out without too much work if you want to go that way in terms of flushing the cooling components one by one. To do it, remove the glove box(es) and disconnect the two levers for temp and air control from the control arms (and the fan switch electricals), the wiper arm decker panel, air filter assembly and four bolts (two each side) at the base of the heater unit itself. All of this is straightforward if a bit fiddly under the dash.

Gently pull/pry the unit loose from any sealant/glue holding it in place, taking care not to damage the one-piece rubber seal btw unit and body. Getting the thing out of the car is easy at this point, just mind the angled control arms that have to come out sort-of sideways through the bulkhead. You might want to replace the insulating foam there afterwards.

If you want to pull the matrix out without removing the whole unit, you risk damaging both as you can't avoid having to bend quite a bit of tin away to get at it. Having it all out also allows you to get rid of rust and dirt particles gathered within the heater unit. I've had that stuff come into my eyes plenty of times at motorway speeds, and it stings. If you do have the unit out, take care not to ruin the frail old foam covering the air flaps.

My last P6B was my all-year driver, and I was happy about the heat I got out of it even on shortish commutes last winter.
 
OK, found the transmitter. It went into the red. So I think I need a new one. Any idea where to find one.

Thanks for all the guidance. I'm pretty sure there's more to learn.

Thomas
 
thob wrote,...
Any idea where to find one

Hello Thomas,

Just pop along to your local Land Rover / Range Rover parts centre and purchase a temperature transmitter for the Rover V8.

The specific part number for the transmitter as fitted into the 3.5 litre V8 engine within the P6B with or without air conditioning is 568055. Current Land Rover issue have part numbers PRC6317 for 3.5 litre engines with air conditioning and GTR108 without . Why there should be one for each I cannot say... :?

Ron.
 
Hi,

got a new termperature transmitter in the meantime. How much coolant do I need to drain to replace the old one - 1 pint or 2?

Thanks Thomas
 
thob wrote,..
How much coolant do I need to drain to replace the old one - 1 pint or 2?

Hello Thomas,

I have not measured the exact amount, but when you turn either tap on the side of the engine block, just let it flow until it stops, collecting it in a clean bucket if it is less than 12 months old and you wish to reuse it. Turn tap to off and away you go.

It has been a while since I lasted removed a temperature sender, but I dare say you will find it rather tight, so be sure that the spanner that you use is a ring spanner of the exact size...nothing worse than rounded edges.

Ron.
 
I don't drain the system to fit a sender unit. Make sure the sytem isn't under pressure, and the rad cap is ON, then with the new sender to hand, undo the old one with your hand of choice, cover the hole as it comes out of with the thumb of your other hand, then change senders, quickly removing thumb and screwing the new one in. You shouldn't lose more than an eggcup full of coolant if you get it right, then top up if needed after running and cooling.
 
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