Help - Rover V8 Thermostat Bypass.?
Discussion
Hi,
I'm writing a bit for Sprint about the Pre-serpentine Rover V8 cooling system, a.la my 93 4 litre Chimaera, and from my own inspection of the system and understanding of it, there is not a thermostat bypass present.
Mr Heath on the other hand writes:
..which I don't understand. Any bypass of the thermostat must join the cooling system pipework after the thermostat, but after the stat there is merely the stat housing rising upwards that connects via a bit of flexi-hose to the top pipe joining the Swirl tank, then the flow to the top hose of the rad from the bottom of the swirl tank. Nothing else joining it at all..
Where is the mystery bypass as I don't want to get this one wrong in (s)print..
Any help gratefully received
Cheers
Matt.
I'm writing a bit for Sprint about the Pre-serpentine Rover V8 cooling system, a.la my 93 4 litre Chimaera, and from my own inspection of the system and understanding of it, there is not a thermostat bypass present.
Mr Heath on the other hand writes:
Bible:Chapter 7:Verse 4 said:
"With the pre-serpentine engines, the bypass is part of the engine pipework"
..which I don't understand. Any bypass of the thermostat must join the cooling system pipework after the thermostat, but after the stat there is merely the stat housing rising upwards that connects via a bit of flexi-hose to the top pipe joining the Swirl tank, then the flow to the top hose of the rad from the bottom of the swirl tank. Nothing else joining it at all..
Where is the mystery bypass as I don't want to get this one wrong in (s)print..
Any help gratefully received
Cheers
Matt.
I think you have misunderstood what a bypass is (Steve makes the same mistake in the bible IMO).
The bypass allows coolant to circulate round the engine when the stat is closed - it bypasses the radiator. On the pre-serp engine, the bypass comes out of the bottom of the inlet manfold just behind the stat housing, and feeds into the top of the pump. The heater pipe feeds out of the *back* of the same housing, and typically returns along side the bypass pipe and feeds into the water pump housing too, logically speaking this is another bypass but the restriction of the heater is so high that it doesn't flow enough water to matter.
On the later serpentine/intermediate engines, the main bypass was deleted - allegedly by accident. The very small bypass provided by the heater feed is still present. On some of the later serpentine TVRs, the feeds to and from the heater matrix have been connected together (allowing water to bypass the matrix and so increase the flow rate). This is a bypass of sorts, but not the same thing cooling system engineers normally mean when they talk about a bypass. The flow rate is still very low but better than nothing. (IMO this is one reason why TVR's RV8 engines are so sensitive to harsh treatment during the warmup cycle, but that's another story ...)
Hope this helps with your article ...
The bypass allows coolant to circulate round the engine when the stat is closed - it bypasses the radiator. On the pre-serp engine, the bypass comes out of the bottom of the inlet manfold just behind the stat housing, and feeds into the top of the pump. The heater pipe feeds out of the *back* of the same housing, and typically returns along side the bypass pipe and feeds into the water pump housing too, logically speaking this is another bypass but the restriction of the heater is so high that it doesn't flow enough water to matter.
On the later serpentine/intermediate engines, the main bypass was deleted - allegedly by accident. The very small bypass provided by the heater feed is still present. On some of the later serpentine TVRs, the feeds to and from the heater matrix have been connected together (allowing water to bypass the matrix and so increase the flow rate). This is a bypass of sorts, but not the same thing cooling system engineers normally mean when they talk about a bypass. The flow rate is still very low but better than nothing. (IMO this is one reason why TVR's RV8 engines are so sensitive to harsh treatment during the warmup cycle, but that's another story ...)
Hope this helps with your article ...
Boosted LS1 said:
So when the stat is closed do you think the engine has to have a bypass at all? Or will the pump just cavitate until the stat opens? Would drilling a few holes around the stat suffice as a bypass as well as increasing overall flow slightly?
It ought to have a bypass, and it has a very small bypass via the heater, but this is a mockery compared to the flow that uprated pump is trying to put out. Yes the pump will probably cavitate, frothing the water at the very time when you have the best opportunity to degas it. This is the sort of thing that would cause severe embrassment to a mainstream manufacturer, but for low volume manufacturers I guess people accept that the cooling system is a bit fragile.
Drilling holes in the stat is one approach, not one I particularly like because it stops the stat working properly and can lead to overcooling in very cold weather - but does keep the water moving during the warmup phase and helps bleed the engine.
I use the drilled stat approach , important not to make the holes too big or too numerous, I just use three 3mm holes to reduce the sudden build up of heat and rapid cooling as the stat opens for the first time, what Peter eloquently named the "thermal shock" - wish i'd thought of that phrase.
GreenV8S said:
I think you have misunderstood what a bypass is (Steve makes the same mistake in the bible IMO).
The bypass allows coolant to circulate round the engine when the stat is closed - it bypasses the radiator. On the pre-serp engine, the bypass comes out of the bottom of the inlet manfold just behind the stat housing, and feeds into the top of the pump. The heater pipe feeds out of the *back* of the same housing, and typically returns along side the bypass pipe and feeds into the water pump housing too, logically speaking this is another bypass but the restriction of the heater is so high that it doesn't flow enough water to matter.
Hi Peter,
Many thanks for the explanation.. I fully understand what you are describing, which is basically the circulation route taken by the coolant when the stat is closed.
The named thermostat bypass and the description in the bible saying "the thermostat bypass allows a small amount of water to start circulating the radiator before the thermostat has actually fully opened."..is what threw me off the scent so to speak and was what I couldn't find a trace of.
Many thanks,
Matt
..shpub are you around to comment on this ?
>> Edited by M@H on Tuesday 21st October 10:00
Bit of a post hijack here... *sorry*
If I want tof it kenlowe/pacet electric fans to my V8 and use the standard 90 rad, is it possible to have the water pump going all the time? and then have a thermostat to the fans so they come in when hot.
The only problem I can see is over-cooling in cold weather as the airflow through the rad will be fairly large.
Whats the best way to do it?
Ta chris
Edited because im a spaz @ spelling
>> Edited by All Terrain on Tuesday 21st October 10:55
If I want tof it kenlowe/pacet electric fans to my V8 and use the standard 90 rad, is it possible to have the water pump going all the time? and then have a thermostat to the fans so they come in when hot.
The only problem I can see is over-cooling in cold weather as the airflow through the rad will be fairly large.
Whats the best way to do it?
Ta chris
Edited because im a spaz @ spelling
>> Edited by All Terrain on Tuesday 21st October 10:55
All Terrain said:
Bit of a post hijack here... *sorry*
If I want tof it kenlowe/pacet electric fans to my V8 and use the standard 90 rad, is it possible to have the water pump going all the time? and then have a thermostat to the fans so they come in when hot.
The only problem I can see is over-cooling in cold weather as the airflow through the rad will be fairly large.
Whats the best way to do it?
Ta chris
Edited because im a spaz @ spelling
>> Edited by All Terrain on Tuesday 21st October 10:55
Think I see what you're getting at - keep the mechanical pump, take the thermostat out, control the engine temperature by switching the fans on and off via the otter switch.
I would work if you had no ram-air through the rad, but of course this would limit the max cooling available which could be an issue in the summer. A conventional stat and bypass is a pretty good solution as long as they are both fitted and working. You can get a much better solution using a bottom stat but it's hard to find these with the right temperature rating. Hopefully this will improve as their use gets more widespread on production cars.
Its going to take AGES for the car to warm up though, and on a winters day, its not going to get warm enough at all without something stopping the coolant circulating to the radiator..
Edited to add.. no I don't get it... the Water Pump will be on all the time the engine is running anyway.. sorry I'm
Cheers
Matt.
>> Edited by M@H on Tuesday 21st October 12:57
Edited to add.. no I don't get it... the Water Pump will be on all the time the engine is running anyway.. sorry I'm
Cheers
Matt.
>> Edited by M@H on Tuesday 21st October 12:57
I'm confused too Matt
AT Are you talking about replacing the mechanical water pump with an electric one, in this case I believe you'd need to have a 3 way valve running the cooling through a closed loop until the engine is up to temp then gradualy switching the flow through the rad (with associated bleed to avoid the "shock")
Running through the rad all the time will, as Matt says, make the engine take ages to warm up
AT Are you talking about replacing the mechanical water pump with an electric one, in this case I believe you'd need to have a 3 way valve running the cooling through a closed loop until the engine is up to temp then gradualy switching the flow through the rad (with associated bleed to avoid the "shock")
Running through the rad all the time will, as Matt says, make the engine take ages to warm up
I am a bit as well
Was my understanding (only tinkered about with the lr 300tdi with viscous fan) that the waterflow was switched on and off to controll cooling, otherwise it would overcool. Especially with a huge rad and viscous fan whiring all the time.
I''m a novice and just trying to clear things up.
Sorry to baffle you all.
Chris
>> Edited by All Terrain on Tuesday 21st October 19:33
as well Was my understanding (only tinkered about with the lr 300tdi with viscous fan) that the waterflow was switched on and off to controll cooling, otherwise it would overcool. Especially with a huge rad and viscous fan whiring all the time.
I''m a novice and just trying to clear things up.
Sorry to baffle you all.
Chris
>> Edited by All Terrain on Tuesday 21st October 19:33
Not entiery sure what you're after but i fitted an leccy fan to ton my V8 landy, I removed the fan fixed to the water pump leaving it mechanicaly driven. I left the stat in the engine in there, and fitted the fan with a variable cappilery switch, this fits inside the top hose and runs to the control box with a dial on top. the engine heats up with the fan off, when the stat opens hot water flows over the cappilery sensor thinggy (technical term) and you can use the dial on the control box to adjust what temp the fan cuts in.
All Terrain said:
I am a bit
Was my understanding (only tinkered about with the lr 300tdi with viscous fan) that the waterflow was switched on and off to controll cooling, otherwise it would overcool. Especially with a huge rad and viscous fan whiring all the time.
I''m a novice and just trying to clear things up.
Sorry to baffle you all.
Chris
>> Edited by All Terrain on Tuesday 21st October 19:33
Hi.. you've got it a bit confused, the fan switches on and off to prevent overheating controlled by a fan switch (otter switch) on a TVR, and with a viscous fan, by another temperature sensetive arrangment I'm not to clued up on, it doesnt run all the time. The Thermostat opens and closes to prevent over cooling (and provide quick warm-up).. The pump runs continuously, driven off the fan-belt.
Cheers
Matt.
>> Edited by M@H on Wednesday 22 October 10:30
M@H said:No the viscous fan runs all the time
and with a viscous fan, by another temperature sensetive arrangment I'm not to clued up on, it doesnt run all the time.
At idle the fan turns at the same speed as the water pump (where the fan is bolted) the idea is that at higher revs the the coulping allow the fan to slip so that engine opower isn't used to turn the fan any faster (to avoid using valuable engine power) the problem is that even this uses a fair rew horspower (I've read up to 10 at high revs) that's why you should rip it off and a dd an electric fan if at al possible (unless you're always driving round at low revs, which seems unlikely)
Aha! That how stuff works is a viscous. I thought the stat turned the pump on and off! 
So basically I rip off the viscous and let normal ram air do its job, untill it starts to get a bit warm and the kenlowe kicks in! SORTED
Now why are you talking about drilling the Rv8?
Will I be having to do this on my 3.5 carb. (from an 82 raro.)
So basically I rip off the viscous and let normal ram air do its job, untill it starts to get a bit warm and the kenlowe kicks in! SORTED
Now why are you talking about drilling the Rv8?
Will I be having to do this on my 3.5 carb. (from an 82 raro.)
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