I think I have found conflicting information. So I'll ask:


Does the coolant flow from the water pump via long pipe to the upper heater port, then out of the lower port to the valve then to the manifold?


or is it the other way around, which to me makes more sense.


does the valve stop the coolant before it reaches the heater? or after it comes out.


simple question, but hanging me up.


1977 xj6-c


thanks all.
geneo

 

I have no clue what goes on there.

all I know is that the heater valve is always "normally" OPEN, which must mean that coolant is always flowing through the heater core unless the TEMP is moved to 65 then the valve CLOSES.

 

Cooant/water/whatever, ALWAYS flows thru a heater core Bottom to Top.

Clearly there will be cars with exceptions, but we are dealing with REAL cars here, and that is how is has been since my mighty MK7 a very long time ago.

 

yes, real cars alright, not to mention hand-built.

 

Ok, how about this picture. which way does the coolant flow?

 

Simple.

1) C41957/C45016 is HOT to the tap
2) CAC2917/C41021 is HOT tap to heater core inlet.
3) C43896/CAC2646 is "cold" from the heater core, then travels done the metal pipe into the suction side of the water pump, just behind the distributor.

 

Jaguar heater valves or "servos" were always "Normally CLOSED" and they opened when you turn the temperature dial to HEAT. Logical. This was like that all the way to the Series 2 XJ6/12 when Jaguar went with a "Normally OPEN" heater valve.

 

That is my take. Normaly open. So, hot water ism in the pipes and matrix all the time


I decided to change that. No heat in the cabin in the summer!! My objective.


So, I added a manual valve in the hose that did not have the vacuum operated on/off valve. Off in the summer on my manual did that. On with a fan and get power vent sans heat.


I call that hardware store source manual valve. my winter/summer valve.


I went to market yesterday., Cool almost cold weather. Nice Jaguar heart!!


Carl

 

HOT water/coolant always always always travels FROM the water pump TO the valve and on to the core.

I can tell you what happens when you get it backwards......
(';')

 

Sorry to disagree.. maybe on older carbed engines but with FI things are a bit different.


TBI ENGINES

Long hose comes from heater outlet to radiator return nipple. Hot coolant comes from rear of intake manifold into the heater valve. Restrictor plates are used in the intake manifold gaskets to block the rear coolant head ports and thereby direct some coolant through a short hose from the heater coolant outlet (at rear of the intake manifold) to the heater valve..through heater core then back to radiator.



Lots of confusion as GM changed some things over the years.

 

Trivia question: Anyone know why Jaguar switched? Hint: typical Jaguar.

 

 

Alan,


The GM thinking has changed with the introduction (back in 1988 or so) of EFI engines. Mine is a TBI version. And after researching "why do I have these restrictor plates blocking the intake rear water passages from circulating coolant through the rear of the block" ?



ANSWER:



Because the GM engineers wanted to keep the bottom of the intake manifold up to temperature (to prevent the throttle body from icing up during cold weather operation).


So they routed the coolant from the front of the engine (water pump)
through the lower portion of the intake manifold and redirected some of it out at the back of the intake manifold at the heater pipe outlet. They redirected the coolant by blocking the rear water passages (with restrictor plates) and forcing some of the coolant to the heater. Also the coolant returned to the front of the engine going through the heads and out the front of the intake to the top of the radiator.



After reading articles from various GM related EFI bulletin boards / forums

I discovered that TBI engines have a different way of circulating coolant. Does not affect other GM V8s but it does pertain to mine.

 

I want to thank all the experienced Jaguar owners that continue to post valuable information in the forum. Sometimes you help me solve problems, on rare occasions I can add something I've learned (usually the hard way), and like this thread on coolant flow through the heater core, you just help me to verify that my car is put together properly. I have an SIII with a small block v8 that previous owners put together. Some things they did beautifully and others "what were they thinking". I have owned dozens and dozens of cars over the years but my lumped SIII is my favorite.

Jeff

 

Sorta like the Jaguar engineers themselves, eh ?

Cheers
DD

 

I'm pretty sure having the heater valve open at all times (except during max cooling) is common with automatic climate control systems (versus manual control systems).

Cheers
DD

 

My way of thinking is that the Delanair in our Jaguars cares not as to which engine provides the hot water. So, only where to tap the pipe to the lower part of the core via the water valve is the question. flow in the matrix is best from bottom to top. Physics. Heat rises!!!


Then the return line goes back to the engine. To the Pump intake to be moved through the engine to acquire heat.


Now, my LT1 features what GM thought up. Reverse cooling. from rear to front!!! My water pump has two spigots, in and out for the heater. In turn the pump is mounted in the center of a manifold of the two banks. Hot out cold in suits the matrix just fine. Still controlled by the Jaguar vacuum operated water valve.


Oh, the LT1 is happy at 190 to 200 F.


Carl

 

The GM thinking is that they try to restrict the amount of coolant that goes through the heater core by placing a restrictor in the hose to heater and the extra coolant then circulates through the engine back to radiator instead of all of it going to heater... core to help with cooling.



There are various ways to route the coolant when it comes to FI engines.

 

Hm, I sure am not an expert in thermal hydraulics! I coined that term!!!!


But, it seems that if added cooling was the incentive, flowing as much coolant as possible through the heater matrix would work. The matrix is a small radiator and transfers heat from the coolant !!


An old tech and highly uncomfortable way to deal with an over heating engine, As it usually happens in hot weather. Turn on the heater!!!!!


Carl

 

Oh yeah, I remember that Carl. That and some prayers you'll get up the hill and traffic will subside before you run out of coolant. I usually carried some gallon jugs of water in the car, just in case.