Any tips on replacing the water pump on a '68 for a newbie?

[tdskip]

Hi Dan, thanks for the note. Glad your set is working, hope it continues to.

I found a couple hose sections that help, posted the Dayco part numbers to help anyone else who goes down this path.

Hopefully I am a couple hose clamps away from being done with this part of waking her up.

I do want to stress that Matt at Vicks has been very responsive and updated their product page.

[tdskip]

Started to fill her up with coolant and discovered that I have a bad leak in the heater return pipe, will need to fix or replace or blank that off.

[tdskip]

Mark Allison is sending me a new return pipe, I realized, which he confirmed, that there needs to be flow there or the back of the engine is going to get hot .

[18Fiatsandcounting]

I realized, which he confirmed, that there needs to be flow there or the back of the engine is going to get hot .

Yes, good advice. If the heater outlet at the back of the cylinder head is just capped off , the water pump will pump coolant into the front of the engine, only to exit out of the thermostat housing at the top front of the cylinder head (the closer and bigger "exit" path). Coolant towards the rear of the block and head won't circulate and will get increasingly hotter.

However, one question pops into my mind: Isn't this the same thing as when you have the heater core and hoses properly connected, but you're driving around with the heater valve turned off? Coolant will be in the heater pipes and hoses, but it isn't circulating very well towards the rear of the engine if the heater valve is closed. Perhaps a non-ideal design "feature"?

Again, sorry to hear of all your trials and tribulations, but it sounds like you're getting closer to having it sorted out. I'll be interested in how it turns out.

-Bryan

[tdskip]

I've already removed the valve I installed for exactly the reason you mentioned, good idea poorly implemented due to my lack of knowledge.

I very much appreciate you calling it out.

[18Fiatsandcounting]

Nope, no lack of knowledge on your part, and I was actually beating up on the original Fiat design!

-Bryan

[aj81spider]

I admit to being a little confused by this. Could someone explain why blanking off the heater pipe isn't the same as turning the heater valve off in the cabin? Isn't there going to be no coolant flow if you have the heat turned off?

This is an important question to me, because I was thinking about installing a valve on the hose going from the top of the engine to the heater box, as my valve never really shuts off and I get heat down there all summer long.

[tdskip]

Good morning AJ, get a more experienced second opinion before making decisions on this but here it goes.

1) coolant flow makes it's way through the engine to the back of the head

2) hose from back of head allows hot coolant to exit the head into the metal heater pipe which has a nipple that diverts some of the flow to the inlet of the cockpit heater assembly. Your car should have two hose stubs on the firewall, one for hot coolant to the heater and one returning the hot coolant post heater to the heat pipe.

3) the metal heater pipe returns coolant to the back of the water pump where it flows into the radiator for cooling.

If you block the flow from the back of the heat to the water pump the back of the engine will not be properly cooled and eventually bad things will happen.

If you allow that flow, but take flow out of the heater circuit (into / out of stubs on the firewall) you are OK.

EDIT - what I did, knowing my heater core was already bypassed and 99.999% likely to leak coolant into the cabin, was to route the coolant from the back of the head to a heater return pipe without the fittings to divert hot coolant to the heater stubs, this way no leaks and it goes directly back to the water pump. My heater pipe only has two opening, one for hose from head and one where it attaches to the water pump.

[18Fiatsandcounting]

A.J., the more I think about your question, the more I realize that I don't have a good answer. It seems like it would make no difference whether the heater core hoses were capped off, blocked with a user-installed valve, or the OEM heater valve is simply in the "off" position. The end result is that there is no coolant circulation between the outlet at the rear of the head and the inlet pipe that goes under the exhaust manifold to the water pump.

I guess the best solution is to have the heater core and valve connected and working as they should, as that has worked just fine in many spiders over many production years. Anecdotally, having an operational heater core and valve has definitely saved my engine from overheating numerous times in the past on super hot days while climbing a mountain or whatever, as uncomfortable as it may be to run the heater and interior fan under those conditions...

-Bryan

[18Fiatsandcounting]

If you block the flow from the back of the head to the water pump the back of the engine will not be properly cooled and eventually bad things will happen.

Yes, but if you turn off the heater valve in the cockpit (via the lever next to the handbrake), isn't this exactly the same result? No coolant flow from the top rear outlet of the cylinder head back to the heater return pipe. And yet this seems to work just fine for Fiats over the years with no problems that I have heard of.

-Bryan

[tdskip]

Bryan - if the heater shut off valve is functioning and doesn’t leak then the answer is absolutely same net effect.

It it does leak then you are going to get unwanted heat and/or leaking from the heater core if it is compromised.

Agree that the best solution is to “just “have everything functioning as fiat designed it, and also agree that the heater trick is an important one to have up your sleeve if the car is running hot.

In my situation – and this is my specific situation – I know the heater core is bad and I just want to get the bloody thing running and driving so this was a easy fix. Being in SoCal I can get by without a heater even though it is still handy to actually have one.

[18Fiatsandcounting]

tdskip, I think we're in total agreement.

I think I mentioned this before, but one easy solution (if you haven't done this already) is just to connect the coolant outlet port at the rear of the cylinder head to the "input" of the heater return pipe. 5/8" coolant hose if I recall, of a suitable length. You can install a valve in this line if you want, but you can also leave it open all the time.

I lived in Pasadena for 6 years, and that "reserve radiator" in the form of the heater core was definitely needed in my '69 Fiat on really hot days on the freeways.... 100 oF days + Stop-n-Go traffic + 2L engine with original '69 radiator = right on the margin of overheating, but the heater core saved the day (albeit somewhat uncomfortable for the driver). I survived, as did the engine.

-Bryan

[tdskip]

Thanks for the, per usual, thoughtful response Brian.

That is exactly how I have the hose hooked up now, test fired the engine with coolant in it and so far so good, couple minor drips from needing to further tighten hose clamps but it looks like I’m close to being set here.

Thanks!

[aj81spider]

I've done some searching on this topic and I think I found some useful information.

http://www.fiatspider.com/f15/viewtopic.php?t=32138

http://www.fiatspider.com/f15/viewtopic ... 15#p125549

If I am interpreting them correctly (and feel free to correct me if I'm not) - the coolant enters the engine at the water pump and is pushed into the block. From there it moves up into the head through a series of holes in the head gasket and head. Generally the system tries to push more of the water up through the back of the head.

The water then flows forward through the head until it reaches the exit port in the front of the engine, which sends it to the radiator. On different model years the hose/thermostat arrangement is different, but on all of them the water is exiting the head in the front.

The port that sends the coolant to the heater core is at the back of the head, and does not contribute (normally) to the cooling of the engine, as the heater valve can be closed. The coolant from the heater core is routed back through the firewall to the metal pipe that runs the length of the engine and dumps back into the water pump.

There is at least one comment that blocking off the pipe is not recommended as the head can use all the cooling it can get. I'm not sure I buy that (although the person making the comment knows orders of magnitude more about Fiat's than me), as normally there is no coolant flowing in that pipe, since the heater valve is off.

I think adding a shutoff valve to the hose that exits the head and goes to the firewall would be fine, as it would simply perform the same function the heater valve does, only earlier in the fluid circuit.

[18Fiatsandcounting]

A.J., your description of the coolant system sounds totally right to me.

-Bryan