Discussion
Hedgehopper kindly pointed out that inserting a water shut off valve in the heater feed from the inlet manifold might not be prudent as it would prevent water circulation on warm up before the thermostat opens. A bypass pipe is supposed to be fitted that allows circulation to continue even if the normal Heater electric valve shuts off the supply to the heater. Following the water plumbing carefully my 96 500 does not appear to have any form of heater bypass and as far as I know it is as original and there are no signs of alterations. Where is the bypass located? Or were some cars not fitted with a bypass?
My V8S has a bypass with the feed and return hoses each fitted with a 'T' connector at the bulkhead and the third branch of each is connected together, so the pipes form a 'H' arrangement.
The diameter of this is so small (prob about 6-7mm) that I can't imagine that it is crucial in any way, I'm guessing its more of a bleed than an actual coolant passage.
The diameter of this is so small (prob about 6-7mm) that I can't imagine that it is crucial in any way, I'm guessing its more of a bleed than an actual coolant passage.
The plumbing varies across the pre-serp & serps, the inlet manifolds and water pump are completely different.
It does confuse me with the serp arrangements that when the heater is closed there is no apparent circulation - probably why they get so many problems with air locks if the heater valve closes properly - and the 'heater is always on' for those that don't..?
It does confuse me with the serp arrangements that when the heater is closed there is no apparent circulation - probably why they get so many problems with air locks if the heater valve closes properly - and the 'heater is always on' for those that don't..?
Did read the other post and now this... I don't know the answer either but did once do a similar thing in a V6 Ford.. result was a 'Ping' as a piston ring went after a few miles... No more damage as I caught it in time... but just take care! Don't want to have the engine in bits mid summer! 
I have to admit that I have not actually seen the heater by-pass arrangement on my '97 Griff. However p.110 para.4 of the 'bible' says, 'Check that the heater by-pass hose has not been removed'. This article was with regard to minimising detonation and subsequent engine damage. Also if you look at the top pic.on p.120 it shows that whilst the thermostat is shut the only waterflow through the cylinder block is via the heater circuit. The idea of putting a valve in the heater pipe is a great idea but I'd like an expert to tell me it's safe before I follow suit.
The enclosed pic,(found somewhere on Pistonheads) shows a by-pass arrangement, but whether it's off a pre-cat or serp. I'm not sure.
The enclosed pic,(found somewhere on Pistonheads) shows a by-pass arrangement, but whether it's off a pre-cat or serp. I'm not sure.
Thanks again for the cautionary warnings.
Had a word with my local TVR workshop manager who said that they had never seen a heater bypass on the later cars they have serviced, and they must have seen scores. Also he could not see a problem with fitting the mechanical valve as it is doing no more or less than the electric one when working properly. Thats good enough for me!
Had a word with my local TVR workshop manager who said that they had never seen a heater bypass on the later cars they have serviced, and they must have seen scores. Also he could not see a problem with fitting the mechanical valve as it is doing no more or less than the electric one when working properly. Thats good enough for me!
Hi,
yes no H shaped bypass on my 94 serpentine Griffith. Looking at the hose and pipe layout under the passanger dash I can't see where one would have fitted easily. I made one up from two pieces of plumbers copper T pieces. With tweeking I fitted it between heater valve and the steel heater pipes. I think the best option would to have a cross over pipe welded between the 2 steel water pipes - originally where I thought the bypass was located.
Oz
yes no H shaped bypass on my 94 serpentine Griffith. Looking at the hose and pipe layout under the passanger dash I can't see where one would have fitted easily. I made one up from two pieces of plumbers copper T pieces. With tweeking I fitted it between heater valve and the steel heater pipes. I think the best option would to have a cross over pipe welded between the 2 steel water pipes - originally where I thought the bypass was located.
Oz
I was down at Dulfords today and mentioned this thread to Richard whilst I was there. He confirms that whatever the bible might say the Serp engine doesn't have a by-pass. This is one of the reasons why the heater valve,if not shutting properly, flows hot water,i.e.there is no other route for the water to go. He also suggested making a by-pass between the two steel pipes running alongside the rocker cover. He suggested that it should be of a slightly smaller bore than the main pipes so as to induce the water to flow through the heater if open, rather than take the shorter by-pass route. This could also include Loubaruch's original idea of a supplementary shut off valve.
The Ginetta system (pre serp) did not ever have a heater by pass, and it causes the temp to fluctutate badly. I think this is due to air pockets behind the thermostat, so it does not open until things are getting a bit too warm. An easy fix was to remove the stat, and enlarge the bleed hole slightly. This may have a small "valve" fitted that can be removed. I opened mine up to 6mm, but this is too large, and the engine takes a long time to reach 80'c, so i would say 4mm would be OK, and make sure the hole is at the top when you refit the stat'. Easier than altering the plumbing.
blitzracing said:
The Ginetta system (pre serp) did not ever have a heater by pass, and it causes the temp to fluctutate badly. I think this is due to air pockets behind the thermostat, so it does not open until things are getting a bit too warm. An easy fix was to remove the stat, and enlarge the bleed hole slightly. This may have a small "valve" fitted that can be removed. I opened mine up to 6mm, but this is too large, and the engine takes a long time to reach 80'c, so i would say 4mm would be OK, and make sure the hole is at the top when you refit the stat'. Easier than altering the plumbing.
I thought the pre-serps had a bypass pipe built in between the inlet manifold and the back of the water pump?
Ant. said:
blitzracing said:
The Ginetta system (pre serp) did not ever have a heater by pass, and it causes the temp to fluctutate badly. I think this is due to air pockets behind the thermostat, so it does not open until things are getting a bit too warm. An easy fix was to remove the stat, and enlarge the bleed hole slightly. This may have a small "valve" fitted that can be removed. I opened mine up to 6mm, but this is too large, and the engine takes a long time to reach 80'c, so i would say 4mm would be OK, and make sure the hole is at the top when you refit the stat'. Easier than altering the plumbing.
I thought the pre-serps had a bypass pipe built in between the inlet manifold and the back of the water pump?Sitting here at work mulling over a problem with a very slow leak in the passenger footwell.
I have removed the H section gubbins and associated pipework and heater valve pictured above and replaced it with a copper U thing I made and drained the matrix, so I know the matrix or associated pipework isn't the source. And before you ask, my new plumbing isn't the source of the leak
I suspect the 90deg plastic bend thing which turns the pipe coming through the bulkhead through 90 to go down the tunnel sidewall but I can't get that any tighter.
Is it easy to pull the pipes off the back of the engine and stick a loop in up there to eliminate the daft plastic things?
I'm wondering if that wouldn't be a quick and better solution for my trip.
Oh, pre-cat by the way, since it appears to make a difference.
I have removed the H section gubbins and associated pipework and heater valve pictured above and replaced it with a copper U thing I made and drained the matrix, so I know the matrix or associated pipework isn't the source. And before you ask, my new plumbing isn't the source of the leak
I suspect the 90deg plastic bend thing which turns the pipe coming through the bulkhead through 90 to go down the tunnel sidewall but I can't get that any tighter.
Is it easy to pull the pipes off the back of the engine and stick a loop in up there to eliminate the daft plastic things?
I'm wondering if that wouldn't be a quick and better solution for my trip.
Oh, pre-cat by the way, since it appears to make a difference.
Edited by Barreti on Tuesday 6th July 12:22
Some of those pipes have a very subtle change in diameter IIRC Ian.
Kitchen roll to identify the joint leaking and then reassemble it with a bit of non-setting sealant may do the trick. I too had the suspicion the plastic was broken but it's pretty tough
If I was ever to look at it again, I thing I'd replace with the flexible spiral bound silicone hoses from bypass to manifold.
Kitchen roll to identify the joint leaking and then reassemble it with a bit of non-setting sealant may do the trick. I too had the suspicion the plastic was broken but it's pretty tough
If I was ever to look at it again, I thing I'd replace with the flexible spiral bound silicone hoses from bypass to manifold.
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