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Club Barge
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Discussion Starter #1
The failure of the heater bypass valve can be seen in a couple of ways.

1 - Water leaking around the back of the engine
2 - Air being drawn into the system, causing over pressurisation.

Replacement is not all that complex and takes around 2 hours, if there are no complications. Below I have detailed the steps to removal.

- Have a tub to collect all the parts in.

1 - Remove the front air pipes from the multiram.
2 - Remove the IACV
3 - Unplug the TPS sensor plug
4 - Remove the torx bolts from the EGR bracket.
5 - Using a 17mm spanner to hold the mounting point, and a 19mm to undo the collar, remove the brake servo pipe.
6 - Remove the bolts from the plenum chamber, remove plenum and place to one side.
7 - Remove the wipers
8 - Remove the scuttle.

You will now be able to see the heater bypass valve. It has a vac pipe going into the top, and three coolant pipes coming into it. There may be some water staining around the area, which is a sure sign that something is not quite as it should be.

At this stage I tend to unplug the large pipe going into the brake servo and move the whole lot to one side. For reference, it may be an idea to mark each pipe to connector, with some different colour paint pens. Else, from what I observed, the pipes goto the following areas.

Nearer servo

2 connectors, total of three pipes. Single pipe goes to vac resevoir above pollen filter. Double pipe, one to car interior, other to front of car.

The vac pipe atop the heater bypass valve goes into the car interior.

NEXT STAGE

1 - It is recommended to drain the cooling system before proceeding.
2 - Carefully remove the vac connector from the top of the HBV.
3 - Undo the single pipe on it's own, plug with rag and place rag under it to catch any drops.
4 - Remove the double side pipes, remembering where they go.
5 - Offer up new HBV, and plump in.
6 - Plug back in vac pipe and valve should naturally sit round the back of the engine, near the bulkhead.

WORST CASE

I found on the car I was working on, that a previous owner had pushed the pipe going from the HBV to the interior, just into the hole, as it had snapped off. If this pipe if not connected, you have no vacuum, and no heat. I effected a repair in the following manner. Ideally you'll need more than one person to assist you.

1 - Find a small piece of rubber hose, large enough to accept the plastic heater bypass hose.
2 - I found the rubber tube I used (around 8mm diamater) large enough to sit into the recess on the rubber bung where the two matrix pipes and other vac pipe go.
3 - Using hermatate and some glue, fasten the pipe here, hold in place and smear the hermatate round for a good seal.
4 - Holding the pipe, carefully push the heater bypass plastic tube into there.
5 - Hold in place for a further 3/4 minutes to let the glue and hermatate set.

The ideal fix is to trace the vac pipe back (I believe it goes to the dials on the instrument panel) and replace the pipe, but this fix seemed to work for my situation.

RE-ASSEMBLY

Re-assembly is reverse of removal. You can attack the following job whilst all the area is stripped.

- Clearance of crankcase breathers. http://www.vauxhallownersnetwork.co.uk/showthread.php?t=83661

Re-assemble and refill the coolant with a 50/50 mix. Take the chance to flush the rad through, and the system if required. Make sure both heather controls are on full hot.

Run the engine up to temperature, and check the HBV for leaks. Also check the heater is blowing hot. If it is, the issue is resolved.

SCUTTLE RE-ASSEMBLY

A little trick pioneered to good effect by Eighth_dwarf, is to smear some vaseline around the mounting foam bit around the wiper spindles. When the scuttle goes back down, this will allow the scuttle to seal. We have discovered it can leak, in some cases, all over the drivers side rocker cover!! (not good).

POSSIBLE FUTURE PROBLEMS

If the unit has been spraying water, then the DIS pack may have limited life left. Be prepared to budget for a replacement.

HTH

James Copp-Taylor
 

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Good job, but can you help out a non-mechanical mind and tell me what IACV and TPS are pls? - I'm sure it's obvious and I'll feel foolish but I can't think of what they might be..:mmmm
 

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IACV = Idle air control valve TPS= Throttle position sensor
seastate said:
Good job, but can you help out a non-mechanical mind and tell me what IACV and TPS are pls? - I'm sure it's obvious and I'll feel foolish but I can't think of what they might be..:mmmm
 

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Club Barge
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3,467 Posts
Discussion Starter #5
Excessive maybe, (though I don't think so) but when working on these cars, I found that having as much space as possible saves problems, this job threw up a number of issues that meant that removal of the plenum was needed.

James.
 

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Heater by pass valve replacement.

Rather excessive.

I was able to replace it without removing the plenum or anything else. Whole job took ~15 minutes.
Hi,
I'm new to this forum. I have a heater by pass valve leak on my 2.5 omega and have just read your thread where you mention you had replaced one within 15 mins.

Can you take me through your (quick) method of replacing it. I dont fancy spending half a day stripping the intake manifold off etc etc.

Many Thanks

Ray.
 

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Hi,
I'm new to this forum. I have a heater by pass valve leak on my 2.5 omega and have just read your thread where you mention you had replaced one within 15 mins.

Can you take me through your (quick) method of replacing it. I dont fancy spending half a day stripping the intake manifold off etc etc.

Many Thanks

Ray.
I did my one by removing only the scuttle and wiper motor.
Took about 30mins in total inc. refilling the coolant.
 

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Thanks for the clues on how to tackle this job. Having now done it, in my opinion it is a total pig, even with the plenum out of the way. Now fear a stressed water pump from losing coolant, based on squeals at idle.
 
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