hello all,
I have a v8 powered locost and am just getting to grips with it after my first six months of ownership.
I'm a bit confused about its temperature and what its trying to tell me. I've done a fair bit of driving including being stuck in traffic
for quite a while (45 minutes stop start in queues etc) and its been fine and hasn't overheated. it tends to sit at between 95 and 115 on the
dial while doing that. and this has been mainly during sunny weather so hot outside temps.
yesterday i took it for a hour on a half drive with a mix of b roads and motorway. it was 10-13 degrees outside and when up to temp it sat at about
85-90 whilst in town and on b roads. when i got on the motorway however the temperature got hotter, up to 100, whilst only doing 55-60 mph only to
cool down again when i got off the motorway 45mph.
i'd have thought that although the engine is working harder the cooler air and better flow on the motorway wouldst have got it this hot?
am i wrong ? is it normal?
the car is injection if that makes any difference
Could be a few things:
Slipping coolant pump drive belt.
Insufficient air flow into the rad.
Hot air unable to escape quickly enough - probably the most likely...
Im building a westfield V8 At the moment, and specifically I'm going through the water pump assembly. So, on reading about this subject, there
are a few pitfalls to look out for. One thing that springs to mind is the water pump drive...What system are you running?. There have been some
reported issues where there is not enough contact between the drive bet and the pump (I think this is specifically the serp type set up)....But this
issue can cause all sorts of problems. The other thing is the condition of the pump...the blades are steel and rust, and can loose efficiency over
time. Have you checked for air locks.
Can you give more detail about the entire set up (Carbs?, engine spec, etc).
the car has been built for 18 or so years and in that time has done 8000 miles including a couple of trips to le mans with previous owners. the engine
was originally a 3.5 from a p6 rover, bored out to 3.8. originally on carbs, ten or so years ago it had a range rover hot wire injection system
fitted.
it has a hurrican cam, and has an aftermarket chip in the ecu (cant remember the name)
R1_PETE: I'd looked at the radiator and while i haven't measured it yet it isnt as big as the one i put in my old v8 which was a huge sd1
copy. will have a look at that when i got the car back (its currently having some mods made to the cage)
there currently isnt anywhere for the hot air to escape at the rear of the bonnet, so the insufficient escape suggestion may be valid - the only thing
against this is that its had this set up for a good while and as far as i know been ok.
slipping drive belt, might fit in with this suggestion though, as its worn/degraded over time.
JENKO: what would be the best way to check for air locks? when antifreeze was added it was done gradually with the cap off the expansion bottle and
run to let the bubbles escape, which i thought might be ok, but perhaps not
I would say that 115c is bordering on over heated!! I have a emergency overheat light on the dash that kicks in at 95c and if it comes on I pull
over. In fact I have wired a very small horn to the light so I car hear it as well. I would personally say your heating system is not running
efficiently enough or isn't man enough for the system. My fan kicks in a 88C.
When thinking about cooling vents air pressure is the most important. You need lower air pressure behind the radiator that you've got in front
of it. If the air cannot escape from the engine bay then you might have similar pressures and then no flow through the radiator. Essentially the car
then just pushes the air out of the way. If you put the vents in the wrong place you may accidentally increase under bonnet pressures and reduce flow
through the radiator. Cutting holes 'anyoldwhere' might actually negatively affect air pressure.
Rover V8's don't like running hot due to the aluminium blocks/heads and the steel liners. Although you have a 3.5 which are not prone to
liner issues. I would still say if your hitting 115c then its far to hot. I wouldn't drive mine at those temps at all but I am a nervous ninny
about temps.
I have a 3.9 with a huge fan clamped to a TX1 London Taxi cab radiator. Biggest thing I could fit in the nosecone. When driving its okay but as soon
as I stop the fan kicks in within 2 minutes. When stopped the heat haze literally plumes out of the vents. I am going to cut more vents but I
don't know where yet
As Irony, that engine is being cooked at 115c. The engine runs better cooler, 80 to 90 is about where it should be and where mine runs. . Mine runs a maximum of 90. Anything over and I,d start worrying. I've a Davies Craig electric pump and controller which keeps everything in check and works extremely well. Especially in traffic and when switching off as it keeps ciculating the water and operating the fan to get rid of execcessive heat soak. Fit an oil cooler if not fitted already to help the cause.
The P6 originally had a small pipe coming from the inlet manifold to the top of the radiator to help with self bleeding, it's common for them to get blocked causing similar symptoms to yours , a small drill bit should clear the blockage as well as checking the hose and rad is clear. The all aluminium engine needs decent antifreeze or else corrosion will occur which would also cause your problems as well as blocking the rad . 115is definitely well over for that engine, I would suggest flushing out the cooling system , opening some vents in the rear of the bonnet and perhaps ducting the airflow through the rad. It would also pay to get the engine tested for head gasket failure, the most certain test I know of is a sniff test using an exhaust gas anyliser in the header tank , block tester comes a close second.
Is it possible your thermostat isn't opening as fully as it should? Might not cause a problem at low speeds due to there being less power
produced and thus less heat being absorbed by the coolant but when at higher speeds maybe the coolant simply can't flow enough volume to transfer
heat to the radiator. I would recommend a 74C thermostat or maybe an 82C if you have a cabin heater and need a bit more coolant temp.
As others have said, make sure to flush (and backflush) the system and check the belt etc. I would also agree that 115C is way too high and would be
nervous above 100C personally. I had loads of cooling problems with my V8 and ended up buying a large alloy competition radiator and cutting vents in
the bonnet etc. I also discovered a large chunk of self amalgamating tape stuck in the radiator top hose as this had popped off one of the unions
where it was being used to give a better seal. I have also gone through various schemes of pipe layout and expansion tank plumbing to ensure there
were no airlocks.
The odd thing is it is only running hot at a speed/load range where normally the rad should be over cooling and relying on the thermostat to keep the temperature up.
I'm not sure that's strictly true.
Yes, at high speeds there will be plenty of airflow (unless the air is getting pressurised under the bonnet). But, at high speeds there is more BHP
being generated and therefore more heat being transferred to the engine coolant. So if there was a restriction in the coolant flow between block and
radiator, I think that would tend to show itself at the higher speeds.
It may not be plumbed in correctly so there is no hot feed to the cold side of the thermostat. This is sometimes done by the heater plumbing in some
cars. Impreza turbo being one. In traffic the cold side warms up through thermal transfer and the thermostat opens. When at speed the cold side is
kept cool so the thermostat doesn't open causing the temp rise. The faster you drive the cooler the thermostat the hotter the engine.. Hope that
makes sense.
[Edited on 10/10/16 by B33fy]
[Edited on 10/10/16 by B33fy]
thanks for all the replies guys, will start investigating
paul
Timing all OK? too retarded will cause overheating. Maybe advance is seized? (just chucking ideas out)
Best guess is read is too small/not cooling efficiently. Is cold air ducted to the rad so it can't get round the sides? But a bigger rad could be
tried if possible.
Thermostat not opening fully is a fair idea too (as suggested) so testing or trying without thermostat a good idea. (but replace!)
My little Triumph toledo got a polo rad when I fitted a whopping 100bhp TR7 engine. Capable of cooling much more, but it didn't. Symptoms
identical to yours. Caused, I think, by poor airflow (bodywork shape/grilled design etc) Changing to a passat rad with 50% more surface area solved
the issue. Just done 2000 miles around the UK in 48 hours, no hint of overheating at all.
Sounds to me like the radiators not big enough (surface area or deeper/more cores needed) or not enough air flow. I've had the rover v8 in
several vehicles and they run best in the mid 80c range, rad fans come on at 94c.
115c is waaaayyyyy to hot.
Ian
quote:
Originally posted by B33fy
It may not be plumbed in correctly so there is no hot feed to the cold side of the thermostat. This is sometimes done by the heater plumbing in some cars. Impreza turbo being one. In traffic the cold side warms up through thermal transfer and the thermostat opens. When at speed the cold side is kept cool so the thermostat doesn't open causing the temp rise. The faster you drive the cooler the thermostat the hotter the engine.. Hope that makes sense.
[Edited on 10/10/16 by B33fy]
[Edited on 10/10/16 by B33fy]