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MG TD TF 1500 - Running heater pipe behind exhaust manifold?

I saw a couple of people who ran (or were planning to run) their heater pipes behind or under the exhaust manifold. I find the idea persuasive for two reasons; one it reduces clutter, and secondly the possibility of picking up additional heat from the exhaust.
On the other hand, I'm wondering if anyone has run into problems with water getting too hot from pipes running close to the exhaust manifold?
For those of you who have made this conversion, what have you found?
Thanks!
Geoffrey M Baker

Also, I'm thinking that if I run the pipes this way it might be smart to include a pressure relief valve at the high point in the system, in case of boil over?
Geoffrey M Baker

Hmm. Well, as the the system is not pressurised in the first place (it vents to the atmosphere) how would pressure develop in the first place?
Kevin McLemore

I don't see a problem with metal tubing, but rubber/plastic hoses would probably hardener from exposure to those higher temps and become brittle in a few years.
JRN JIM

Kevin, if you imagine a really hot day and the engine sitting running with the heater not turned on, and the exhaust manifold is getting very very hot. The water in the pipe right behind the manifold might begin to boil. This would create considerable local pressure, expanding along the length of the pipe, disrupting the flow of water by creating back pressure in two directions. That's why I was wondering if a pressure relief valve might be a good idea near the bulkhead at the high point of the piping system? Just a thought. I don't really imagine a problem but thought someone might have already implemented this and would know....

I'm going to use stainless steel tubing Jim, for that reason.
Geoffrey M Baker

How I ran mine. PJ

Paul S Jennings

Thanks Paul. I've studied various setups in the archives quite thoroughly. I just really like the thought of making the heater pipe disappear altogether by running it below the manifold... but there are many very nice setups like yours as well.
Geoffrey M Baker

Just for the record, Triumph ran their water pump heater return pipe under the exhaust manifold for many of their cars without any issues.

GT6:

http://i973.photobucket.com/albums/ae216/CHRIS211083/Spiddy/DSCF4660.jpg

Spitfire:

http://i217.photobucket.com/albums/cc61/chappy444/2011-07-06_16-37-25_779.jpg

Detail:

https://spitfiremk3.files.wordpress.com/2011/09/wp_0000281.jpg
Kevin McLemore

Geof,
Bear in mind, you really don't want to run the return against the exhaust to make it hotter since it is going right back into the engine. That would be counterproductive for cooling.
JRN JIM

Geoffrey, I think you maybe over engineering this. No need for a pressure relief.. As the system is vented. There is nothing to trap pressure to allow pressure to build. Regards, tom
tm peterson

Tom, I want to put a shut-off valve on the heater line coming into the heater. Would this trap pressure? Or would the system be able to vent it elsewhere?
If it can handle a shut-off valve, I won't worry about a pressure relief point.
Geoffrey M Baker

As long as there is just 1 vavlve, it can not build up pressure.
JRN JIM

Geoff, unless you've changed it, the end of the radiator overflow tube is exposed to the atmosphere. Bud
Bud Krueger

I have a question on this subject. Why put in a heater, it was not a factory item, it takes up a hell of a lot of room, and the car puts enough heat in the cockpit to keep warm. up here in the north country, we cant run them in the winter, so no one has them. where you can run them in SW, SE it would seem the heat put out by the engine into the cockpit would be enough to keep warm on a drive. Not knocking the heater but seems a waste to put one in. driving with one takes up a lot of leg movement in that narrow area of the car.
T Maine

The heater came with the car. I don't expect to use it much (but perhaps some days, in the winter). It is of course handy if the engine is getting too hot to run the heater as a way of keeping the temps down - if not a particularly pleasant one for the driver!
Plus, I have to say now I've had the heater powdercoated, I find it very attractive and a nice addition to the car. As far as leg movement? I'm 6' 2" and have never noticed the heater getting in my way.
Geoffrey M Baker

This thread was discussed between 26/01/2015 and 28/01/2015

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