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Heater core & heater valve - which comes first?

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Old Jan 22nd, 2017, 19:10   #1
simonvolvo
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Default Heater core & heater valve - which comes first?

Does it depend on the car model? Does it matter?

In a related thread:
http://www.volvoforums.org.uk/showthread.php?t=262208
Ron posted a diagram which showed that the heater core comes first and then the valve. I and someone else questioned this. In my car (1970, B20) the heater valve comes first. However, my heater hoses are no longer original. Stock, by-the-meter, heater hose has been used. So I couldn’t be sure. The drawings in the GCP catalog (both B18 and B20) correspond to Ron’s arrangement.

Doubt set in. Must I change my hoses? Not exactly a 5 minute job.

I have since looked at some engine bays for 1970 Amazons on the Amazonpictures website:

http://www.volvoamazonpictures.se/Vo...php?start=2361

Working back from the latest chassis number, all of them seemed to have the heater valve first and then the core, like in my car. But none of the pics were very clear ... until I got to chassis 349287 (pic copied hereunder) which leaves no doubt.

According to CVI’s parts list the heater hoses for the B18 and B20 do differ - for the B18 there seems to be only one shaped hose whereas, for the B20, all three the hoses are shaped.

So, was the order changed when Volvo changed from B18 to the B20?
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Old Jan 23rd, 2017, 01:56   #2
Ron Kwas
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Simon;

This is a scan from the factory manual, with my mark-ups:

I hope it helps.

Cheers
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Old Jan 23rd, 2017, 12:44   #3
Derek UK
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To add to that, the blue hose goes to the long pipe that that runs along the block underneath the exhaust manifold. The red hose goes to the brass angle connector in the back of the head. This pic is a bit more complete.
NB The picture of the matrix is wrong. Both of the pipes should come out of the front so they go through the holes n the casing. The one for the lower connection shouldn't be at the back. Bad error there on the illustrator's part. Pic came from here http://www.historic-cars.net/histori...1384-4-Heating

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Old Jan 23rd, 2017, 14:44   #4
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Simon; I don't believe routing shown in that picture is correct...it is certainly not consistent with any actual routing I've seen, or the routing shown in the two graphics here. But to answer the question "Does it matter?"...as I've previously noted, it is a series circuit, so from the point of flow, it does not, and as you've previously also pointed out, the only major difference is that if Heater Core comes first in flowpath, Heater Control Valve would be subjected to the cooled Coolant, possibly being a bit gentler on that component (...but I doubt this really matters, it's certainly not critical, since HVC does come first in other models and vehicles). I guess what I'm saying is, I would change hoses at your next convenience to be consistent with documentation shown (not pull over in a panic-stop and feel you must do it before driving another foot)...it's just not that critical!

If using the preformed OE hoses to make these connections, they do have a preferred placement.

Derek; Error notwithstanding, that graphic is even better!...I have made corrections and added flow info details! Here you go:

Can you find and post Link to a similar graphic for the 1800, so that I can make a similar flow graphic for that model. Tnx.

Cheers

Last edited by Ron Kwas; Jan 23rd, 2017 at 17:38.
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Old Jan 23rd, 2017, 23:23   #5
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Ron, click the link in my post. The page also shows the partial routing for an ES. Interestingly the 1800 does have a pipe out of the back of the matrix which comes out behind the fan housing. The short right angle hose for that goes to the lower tube on the heater valve. The long hose that goes back to the outside pipe that goes back to the pump goes on the top fitting on the valve. Valve is different on the 1800 and has the in/out coming out of the side of a vertical tube. If you don't have an 1800 parts book I will do a screen grab from the one I have downloaded onto my PC.
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Old Jan 24th, 2017, 00:26   #6
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Derek;

In studying that linked site, I have figured out what was wrong with that Graphic...they (wrongly) combined the 122 HCV with HC on an 1800. On the 1800, the HC does indeed exit toward the rear, but the HVC is slightly different again from the 122HCV. I'll see about making a combined graphic which shows both and clears this up.

Cheers

Edit: I just saw your post...looks like we both figured it out!
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Old Jan 24th, 2017, 10:28   #7
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Forum;

Improved Coolant Flow graphic showing 122 and 1800 variations (HCV is on cold side of HC in both cases):

Cheers
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Old Jan 24th, 2017, 14:30   #8
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Thanks Ron. Just sitting pondering the revised illustration, I'm reminded that the matrix will tend to be hot all of the time. Probably not has hot as the block but it is a sort of passive radiator when the valve is shut. That does enable you have warm air as soon as you need it, especially for demisting. Heat will increase quickly once the block coolant starts to circulate through the matrix. With that in mind, those who live in hotter climes and never use the heater might prefer the in out hoses reversed so that the block coolant is shut off by the valve. This should lower the temp of the matrix and possibly reduce the interior temp by a degree or two. Probably not noticeable when running around with the windows open at 40º though. I think Cali has recently had some very welcome rain so demist might have been very useful now and then. Probably caught out a lot of people with worn/dried out wiper blades too but that's another subject. Rainex to the rescue.
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Old Jan 24th, 2017, 15:39   #9
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Derek;

I don't think I can agree with your premise that HCV first or HC first would make a difference in how quickly heat was available from HC. "I'm reminded that the matrix will tend to be hot all of the time." I think this can only occur with a HCV which is not fully sealing, allowing some limited flow in the loop (and HC to be warm). ...but presuming a properly working HCV, that means zero flow in the Heater loop, and that means even when engine is hot, the coolant in the entire Heater Loop is static and therefore remains at ambient.

What do you think?
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Old Jan 24th, 2017, 18:40   #10
simonvolvo
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Thanks for the replies.

I’ve done some homework in the meantime.

I have no doubt that you are right when it comes to the B18. As for the B20, however, I have come to the conclusion that some assemblers (the majority?) must have used a different routing.

I did some scratching around in my old-parts bin and managed to retrieve the old hoses. These are the original, factory-fitted ones. The pic below labelled “WRONG?” shows the way they were connected at the time that I replaced them. I am pretty sure that is also the way they were connected when the car was new. The pic labelled “RIGHT?” shows another way in which it would be possible to connect the hoses.

I trawled through some more pictures of engine bays on the Amazonpictures website. Of the 17 found which showed the configuration reasonably well (all 1970 and 1969 models), 12 have it the “WRONG” way.

The drawings in the GCP catalog are not helpful in resolving the issue. For the B20 they simply copied the drawing used for the B18 (including the illustrator’s error pointed out by Derek). However, the parts numbers they give for the B20 hoses do differ from those for the B18.

If you look at the CVI catalog:

http://www.cvi-automotive.se/en/arti...-heater-system

and cross-reference the parts numbers with those in the GCP catalog, both CVI and GCP appear to base their data on the “RIGHT” configuration (heater core first and then the valve, for both B18 and B20).

Another difference not apparent from the GCP drawings: The free end of the elbow fitting is shown to point in a NNW direction (if you stand in front of the car looking towards the rear). That may be the case for the B18, but in my B20 (and I don’t know if that is true for all B20’s) it points in a NNE direction. Use of “Hose 3” in the “RIGHT” configuration would be rather awkward if the elbow end were to be pointing NNW. I have an idea that this was done in the B20 to allow for some more movement between the engine and the firewall with “Hose 3” in place (and in the “RIGHT” configuration).

On balance I think that “WRONG?” is indeed wrong and “RIGHT?” right.

Whatever it is, it is clearly not mission-critical. I’ll take Ron’s advice and put the whole thing on the back-burner.

The thread can be closed.

PS: I agree with Ron's view about the core temperature when the valve is closed - ambient.
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File Type: jpg 2017_05 001 wrong.JPG (293.1 KB, 10 views)
File Type: jpg 2017_05 001 right.jpg (292.2 KB, 8 views)

Last edited by simonvolvo; Jan 24th, 2017 at 18:45.
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