craig1410
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| posted on 19/4/09 at 01:12 AM |
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Rover V8 blowing out water at low speeds. Ideas?
Hi guys,
Got my RV8 powered locost on the road today and have done a few runs with no major issues. However, I am having an overheating issue where the car
seems fine while out and about at cruising speeds but when I come back into urban areas at 30MPH it seems to get a heat surge and blows water out the
overflow pipe on the expansion tank.
My radiator is getting hot as is my top hose which suggests the brand new 'stat is okay. The 15psi pressure cap is also brand new and is
attached to the donor Rover SD1's expansion tank and I'm sure is working fine. I have 8mm hoses coming from the top of the radiator, the
top hose inline coupler bleed pipe, and the top of the standard SU carb inlet manifold. These hoses all join together via two t-pieces and feed into
the bottom of the expansion tank. The idea being that any air expelled from these areas should find its way to the expansion tank and effectively
self-bleed. I also have a jiggle pin in my 'stat and drilled a couple of extra 3.5mm holes to avoid air locks.
I have a Rover P6 water pump fitted for clearance reasons and my thoughts are that perhaps this less efficient pump is not circulating enough coolant
to keep the engine cool at low RPM.
Anyone seen this sort of low speed heat surge and any ideas how I can fix it?
Thanks,
Craig.
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rusty nuts
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| posted on 19/4/09 at 06:05 AM |
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Check that the 8mm breather on the front of the inlet manifold between the carbs is clear . My old 3500s had cooling problems even after doing the
head gaskets , clearing the breather sorted it. Not a cure but Red Line Water Wetter will reduce the overall temperature by as much as 20 degrees. You
have made no mention of a cooling fan?
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DIY Si
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| posted on 19/4/09 at 08:04 AM |
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I used to get tis with my blackbird engine. Turns out the fan was wired in back to front, so as I was slowing down and driving round towns and
villages it would gradually get hotter and hotter. I rarely noticed as I was looking for someone's house/pub etc. I only noticed the water under
the car. Changing the fan wires round so it went the correct way solved all my low speed heating issues.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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mark chandler
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| posted on 19/4/09 at 08:21 AM |
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Definately sound like the little 8mm pipe blocked from the carb V or going to the wrong spot.
Have you an under bonnet picture?
On a SD1 or classic range rover this pipe went to the top of the radiator, another 8mm pipe vented also from the top of the radiator goes to the
expansion bottle.
If you try and circulate water through the expansion tank it needs to be the highest point in the system, if you follow the above it can be lower
down.
Regards Mark
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Bob C
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| posted on 19/4/09 at 09:33 AM |
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I've had a couple of V8's; you could have airlocks( however small) in the heads - the head design is not great for this & the engine
would have to be pretty horzontal in a locost, so carefully consider exactly where any trapped air would end up.
Also use the lowest temp stat you can get; I think the standard one is 88degrees but you can get em down to 82 degrees.
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britishtrident
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| posted on 19/4/09 at 10:34 AM |
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The descriiption exactly fits an ignition advance curve problem -- ignition is too retarded in the 1000 to 2000 rpm range.
The other thing that might help is fitting the plastic external thermostat used on somes Rangies and Discos, this allows a lot more by-pass flow but
throttles it down when the main thermostat valve opens.
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craig1410
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| posted on 19/4/09 at 10:46 AM |
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Hi guys,
Thanks for your responses - some good suggestions. Taking them in turn:
Yes my breather was cleared out when I installed the engine and flushed the cooling system but it is possible that it has become blocked with
dislodged debris after the engine was run properly on the road so will check. Water wetter may be a good idea once I am happy that the cooling system
is basically working and I won't need to flush or refill it for a while. Good idea!
I do have a fan which came from a VW Golf as did the radiator. The rad is the larger of the petrol Golf/Passat rads and pretty much fills the
nosecone. The fan has its cowling and I'm 100% sure it blows the right way but again a good suggestion.
Regarding the routing of the manifold coolant pipe, I can't really run this to my radiator as per the SD1 because the radiator is lower than the
manifold pipe exit so this would be a sure way to trap air in the top of the manifold.
Here are some pics of my engine bay linky
As you can see, I have a pair of t-pieces arranged as a letter 'H' which turns it into a 4 way coupler. The backward facing branches go to
the manifold coolant take off and the expansion tank respectively and the forward facing branches go to the radiator top hose highest point where I
have inserted an aluminium joiner with 8mm take-off. The other forward facing branch goes to the radiator top bleed pipe. Not ideal by any means as I
would like the expansion tank to be higher but as I understand it this shouldn't matter as it is only there to allow expansion and contraction
of the water volume through the heat cycle and doesn't itself define the water level as such. Obviously I may get some air trapped in the hose
between the tank and the 'H' coupler but again I don't think this is my problem.
I am tempted to change my setup as follows:
1. Connect expansion tank to inlet manifold 8mm outlet (highest point and most likely to see air bubbles in future coming from within engine due to
cavitation or boiling etc.)
2. Remove one of the t-pieces from the 'H' coupling and use the remaining t-piece to create a simple bleed pipe with a bleed nipple or
similar to allow air to be removed from the radiator and top hose. In other words the t-piece would connect to radiator bleed pipe, top hose bleed
pipe and would have a blanked 3rd branch which could be opened up when necessary to bleed the system.
Having the above setup would use coolant expansion and contraction to keep the manifold 8mm pipe clear and should keep the system air free. I might
need to manually bleed the other section from time to time but no worries about that.
Almost forgot to mention, my thermostat is an 82C one which was fitted brand new a few weeks ago. I think you can get slightly cooler ones which I
might look for but it shouldn't over heat at 82C really.
Thoughts?
Cheers,
Craig.
[Edited on 19/4/2009 by craig1410]
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craig1410
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| posted on 19/4/09 at 10:50 AM |
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quote:
Originally posted by britishtrident
The descriiption exactly fits an ignition advance curve problem -- ignition is too retarded in the 1000 to 2000 rpm range.
The other thing that might help is fitting the plastic external thermostat used on somes Rangies and Discos, this allows a lot more by-pass flow but
throttles it down when the main thermostat valve opens.
Hmm, I wondered about ignition timing - I might have a look at that. I did set it at one stage but worth checking again to make sure nothing has
shifted. I'll also double check my crankshaft TDC pointer to make sure it is accurate as I know this can be a problem in RV8's.
Thanks for that suggestion - a bit lateral but in this case that could be just what is needed. 
Thanks to all,
Craig.
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mark chandler
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| posted on 19/4/09 at 12:24 PM |
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Hello
Yes the 8mm needs to be able to bubble, so if you do what you suggest and just plug this alone into an expansion tank then this should sort things
out. At present by tee-ing together the pressure is even both sides of the air lock, as the heads heat up it starts boiling creating air which cannot
escape without pushing the water out of the way first.
Regards Mark
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craig1410
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| posted on 19/4/09 at 01:05 PM |
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Will give that a try then and report back. I was never all that happy with the way I had done it but kinda hoped that by coupling all the high points
together, the air would eventually find its way out through the expansion tank but maybe not.
At least by following my proposed new setup the line length between 8mm pipe and expansion tank will be shorter and more direct which in itself should
help. I can also open the bleed screw on the t-piece and see for sure if any air is present.
Thanks again,
Craig.
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craig1410
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| posted on 19/4/09 at 05:04 PM |
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Just a quick update - I tried re-routing hoses as described in my other post and initial indications are good. I carefully bled the system when I had
finished moving hoses and then I set the coolant level to the "normal" cold level. After a 5 minute run out the road and back I had the
temperature sitting at about 100C on the gauge. It was slower to rise than last time I drove it and it sat just below 90C when cruising at 50MPH. Back
in town it climbed to 100C but importantly it didn't through out any water and there was a good 2" of air still in the expansion tank.
I released the expansion tank pressure cap (with a towel) to help purge any air which might not have been able to escape due to being pressurised but
there was nothing more than a couple of bubbles and then the coolant level just came up and spilled down the overflow. I'll watch how the level
drops during cooldown and with a bit of luck it will settle back to the "normal" level. If not then I can top up as required.
100C is a bit high for my liking but that seems to be about the point when the fan thermostatic switch is activated. I think I will fit a manual
override which I can switch on at my discretion.
Might try a longer/faster run after dinner to see if that makes any difference.
Cheers,
Craig.
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rusty nuts
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| posted on 19/4/09 at 05:22 PM |
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You can get a different fan switch to come on a bit earlier. Have a look on the side of the switch , the operating temperatures are normally there. 2
temperatures should be shown, one is the on temperature the lower one will be off. Any good motor factor should be able to help. If you are using the
original VW switch they do tend to operate at higher temperatures
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craig1410
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| posted on 19/4/09 at 11:03 PM |
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Another update, my earlier optimism was perhaps misplaced as I seem to be getting the same issues again. 
I went out for a second run and upon returning the temperature on the SD1 gauge was getting close to 110C and water was coming out the overflow due to
the expansion tank being full to the brim.
I'm going to check on ignition timing tomorrow to see if I can advance it a bit. I am using super unleaded fuel with valve seat additive so I
should be able to throw in a bit more advance without pinking. According to Des Hamill, the best ignition setting is simply as much advance as
possible without pinking. I might also try thermostat removal to see if that solves the problem. If not then I guess it will be the water pump which
isn't pushing hard enough.
Does anyone know of any sources for good value header tanks? Thinking alloy with largish feed hose in bottom and 8mm bleed hoses and a pressure
cap.
Cheers,
Craig.
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02GF74
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| posted on 20/4/09 at 08:17 AM |
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which engine is it?
the 3.9 and other large capacity V8 are notorious for slipped liner problems resutling in water system being pressurised.
also running temps, how do you know the SD1 temp gauge is telling t he truth.
sorry but can you post a drawing how you have plumber the system? (sorry too many words and I do pictures better).
do you have pressure cap on radiator and one on the header tank?
is there a heater in the system, if not, how have you plumbed that part?
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craig1410
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| posted on 20/4/09 at 11:35 AM |
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Hi,
It's a 1976/77 SD1 3.5 litre engine so I don't think the dropped liner issue is prevalent on this engine IIRC.
You are correct, I don't know for sure if the gauge is correct but the engine is very very hot, I can tell that due to the radiated heat and
huge heat haze. Not scientific but definitely a hot engine with a cooling problem. Maybe I will dunk my sender in a pan of vigourously boiling water
and see what the gauge says. Should give me a 100C reference point.
Will try to post a diagram later, need to feed the kids first...
Pressure cap on header tank only, radiator is VW Polo.
No heater, I have just connected the heater outlets together which has made me think a bit...that could be my problem! The P6 water pump is known to
be weak compared to the SD1 pump and I am probably not doing myself any favours by pumping water around the non-existent heater circuit. I did it to
maintain flow around the head prior to stat opening but I expect that is catered for elsewhere because in the SD1 it would need to work with the
heater valve shut as well as open right?
So, what if I blank off the heater circuit? At the back of the engine there is a 16mm and 19mm pipe, one comes from the inlet manifold and the other
comes from a pipe which passes under the inlet manifold and connects to the water pump. Would you agree that having more water flowing through the,
probably open, stat is better than having it circulating through a 180 degree bend and back into the engine? Got to help right?
I think I'll give this a try this afternoon. Failing that I'm thinking of getting a header tank of the self-bleed, full flow type
(header/expansion - never sure which term to use...) Anyway, the Westfield SEight seems to use a Ford Fiesta tank which seems quite shallow and should
be ideal for mounting to my scuttle as high as possible. I will need to set it at the right height unlike my SD1 header tank which can be anywhere.
Will report back.
Thanks,
Craig.
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MautoK
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| posted on 20/4/09 at 01:22 PM |
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Craig,
I've got similar problems to yours in my MK/Pinto/auto. Your last post made me wonder whether the manifold-to-pump loop is too low an
impedance (2 feet of 1/2 inch ID pipe and no heater matrix) as compared with the thermostat + radiator. The thought is that the water is
preferentially being driven around the loop and there is inadequate flow through the radiator (but enough to get the rad hot).
I'm just off to try pinching the loop pipe, probably by the highly technical method of Mole grips and a couple of layers of plywood or aluminium
sheet...!
See my other post...it made no difference
[Edited on 20/4/09 by MautoK]
He's whittling on a piece of wood. I got a feeling that when he stops whittling, something's gonna happen. (OUATITW/Cheyenne)
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craig1410
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| posted on 20/4/09 at 02:36 PM |
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Maybe I'll have more luck...
I'm busy re-routing some wires and brake pipes which were too close to my exhaust manifold are were being cooked. The spiral wrap on the wiring
melted which gave me a clue about the heat they were being exposed to. Once I've sorted that I will try running the engine with the heater
matrix connections blanked off (or clamped off as you did). Will report back later.
Cheers,
Craig,
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craig1410
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| posted on 20/4/09 at 10:44 PM |
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Well I got a quick run in the car this evening and (once again) initial indications are that clamping the heater hose has helped. I drove until the
coolant reached the normal mark and then came home. Once home I let the engine run for a good 5 minutes and although the temperature gauge came up to
100C or so, once the fan kicked in it cooled back down again to about 90C. More importantly the coolant level in the header tank was a couple of
inches clear of the top.
I think I'm moving in the right direction now and if I get a low temperature thermostat & fan switch and wrap my manifolds in heat tape and
fit a couple of bonnet vents to the sides of my bonnet just above the manifolds, I should be in better shape.
Back to work tomorrow so I'll order up the bits and fit them next weekend with some luck. Thanks for your help all.
Craig.
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