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 How to- replace the heater hoses on top of the fuel tank 
Description A cheaper method than getting toyota to do it for you
Author lower Date Thu Mar 24, 2005 8:35 am Type Text How-To

Category Engine
Viewer Comments [2 - Post your comments]
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How to- replace the heater hoses on top of the fuel tank
A cheaper method than getting toyota to do it for you
The brass heater pipes on top of the fuel tank seem to be prone to cracking on the Mk2 and are expensive to replace because replacing them involves removing the fuel tank. To replace both pipes you are looking at approximatly 200 for the pipes themselves + the labour which toyota quote at about 600. They tend to crack where they are bolted to the chassis where they dissappear into the space above the fuel tank in the engine bay behind the heat shields. This area is completely inaccessible to form a repair without dropping the fuel tank. If you do replace the pipes with new toyota ones you will find that a rubber bush has been fitted where the pipe bolts to the chassis to prevent the cracking from reoccuring. obviously toyota acknowledged there was a problem.

When the pipe or pipes crack they tend to do so gradually and the leak can be very hard to find. On my 92 t-bar turbo it took about 2 months of daily use of the car from when i first noticed a drop in coolant levels to when i was able to track down the leak. Because the leak is above the undertrays you often find that coolant runs along the undertrays and can appear in a number of places, making it confusing as to where the leak is coming from. Even when my leak had got fairly bad, i could only see it when the car was stationary with the filler cap removed. With the cap on the system didn't leak unless under pressure.

There is an alternative method to dropping the tank and replacing the pipes with new brass ones. This alternative is to replace the brass pipes with rubber heater pipe that you run along the underside of the car next to the existing radiator pipes under the undertrays. The pipes you are replacing are only heater pipes, and as such you are replacing brass with rubber heater hose, and they overall volume of the coollant system remains basically unchanged.

I wrote this how to some time back:

OK, there are two metal pipes that run from the engine to the heater under the front bonnet. At the engine end you will have to remove the heat shield that covers the entrance to the fuel tank tunnel and you will see the two pipes, i think there is one bolted to each side of the tunnel. Trace the metal pipes back to where they become rubber and then connect onto the engine. At the other end of the car, take the trim off behind the spare wheel and you will see the heater. There are two rubber hoses that come up from under the car and then attach to the heater. These are the other end of the pipes you want to replace.

Get the car jacked up on ramps or axle stands and take off all the under trays. You will see two sets of pipes running under the fuel tank, one is a pair of coolant pipes, the other for the air con. Do NOT disconnect either of these but this is where you are going to run your new set of pipes.

Disconnect the rubber hoses from the heater and collect any coolant that comes out. Remove, or cut back these bits of hose. You then want to buy approx 18ft of heater hose in the same diameter as what you have just removed.

[edit] hose should be 19mm diameter. I bought 18 ft and that was sufficient for me but others have said that the route they took meant they needed a total of 22ft.

Working from under the car, pass the ends of the new heater hose up into the area where the old heater hoses connected onto the heater and conect the new ones on (this bit you will have to do from the top). Then run the new hose along the underside of the car in the gap where the fuel tank is. I managed to squeeze the most of the pipe alongide or above the fuel tank so that no hose stuck out below the level of anything else on the underside of the car. You don't want to foul the undertrays when you put them back on or squash a hose. You will also have to remove a bracket holding part of the handbrake mechanism
to put the hose above it. You can then put that bracket back into place. When you get to the engine end of the car you can follow the path of the existing metal pipes and then the old rubber sections of these pipes. Making sure that the hoses are connected onto the same connections as before (ie new left side hose goes to where the old one was connected) remove the old rubber sections of hose and connect up the new ones. You may then wish to cut the brass sections of pipe back as far as possible so that when you replcae the heatshield there is no evidence of what you have done.

Top up the coolant system with forlife or anitfreeze as required and bleed the air out at the heater. Start engine, check for leaks. If no leaks replace
undertrays and heat shields and the job is done.

After doing this repair it took about 2 months for the coolant levels to stabilise. I found it had to keep topping up with very small amounts of coolant to be able to see coolant under the pressure cap. This may be because it takes a while for the heater hose to stabilise in size, or it may be becuase i didn't bleed the system very well.

 User comments 
poyntesm: Thu Mar 24, 2005 8:35 am     [ KB ] How to- replace the heater hoses on top of the fuel t

[ Article updated...poyntesm ]

Category: Engine
Type: Text How-To

Article Name: How to- replace the heater hoses on top of the fuel tank
Author: lower
Description: A cheaper method than getting toyota to do it for you

>>Read Full Article
barrygadd2003: Sat Mar 01, 2008 12:05 pm    

I have just realised the frustrating water leak in my 1991 MR2 G-Limited is coming from the same heater pipe that you identified in your topic.
I found some months ago the water level needed topping up now and again. I noticed a leak coming from roughly where the radiator pipe drain plugs are and assumed it must be one of these.
I thought I could see 2 heater pipes running alongside the 2 radiator pipes and therefore there couldn't be a heater hose above the petrol tank.... WRONG....
After removing the 2 metal backing plates behind the exhaust manifold shield and feeling around a metal pipe that disappears above the petrol tank I found the leak....
I wonder if dropping the petrol tank is not too difficult?? and trying to bend up some 22mm copper plumbing pipe to replace the existing pipe??
I've done a bit of plumbing and have a pipe bender so it may be possible

I had another MR2 Mk2 where the oil cooling pipe which runs around the engine to the base of the oil filter was also leaking (the guy I bought the car from thought it was the head gasket..) This was another so and so of a job and I found the best way to solve was to remove the cylinder head,remove the cooling pipe completely. Check carefully where the pinhole leaks were and then cut a short length of 15mm copper pipe lengthwise to form a copper patch. Then carefully clean the outside of the steel cooling pipe and the inside of the copper patch and solder them together. A fiddly and time consuming job but it worked very well.
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