[xk] XK 120 very active water pump

I have been struggling with a problem with my 120 for quite a while.
It blows coolant overboard. It does NOT overheat, not even close.
But it has popped two upper radiator hoses, and one bypass hose at
the T stat housing.
With the engine at operating temp. (160 stat), rev the engine to
over 3500 & I can see the upper radiator hose bulging. It has blown
the top radiator hose off of the stub on the T stat housing, with
predictable results. Bypass hose is normal
The water pump is a new manufacture unit for a 120 that is now
perhaps several years old. Been doing this type of behavior for
several years.
Today, I took the T stat out, re-assembled the housing & the
problem is gone gone gone. This tells me that the water pump is
more energetic than it needs to be. T stat is a bypass type non
bellows unit. Other t stats have been tried with similar results.
Anyone else have problems similar to this with a non-original water
pump?

Roger–
Roger, '54 120 M, DHC, BRG, S678300
Tamarac, South Fla., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Roger,
I can’t be of much help, but I haven’t heard of that before. Are you sure that a waterway isn’t blocked. I have an XK140 water pump on my 120. It moves a little more than the standard 120, but it does not blow coolant.
Gotta think about this one,
Knight________________________________
From: Velocette gasssit@comcast.net
To: xk@jag-lovers.org
Sent: Monday, October 10, 2011 1:13 PM
Subject: [xk] XK 120 very active water pump

I have been struggling with a problem with my 120 for quite a while.
It blows coolant overboard. It does NOT overheat, not even close.
But it has popped two upper radiator hoses, and one bypass hose at
the T stat housing.
With the engine at operating temp. (160 stat), rev the engine to
over 3500 & I can see the upper radiator hose bulging. It has blown
the top radiator hose off of the stub on the T stat housing, with
predictable results. Bypass hose is normal
The water pump is a new manufacture unit for a 120 that is now
perhaps several years old. Been doing this type of behavior for
several years.
Today, I took the T stat out, re-assembled the housing & the
problem is gone gone gone. This tells me that the water pump is
more energetic than it needs to be. T stat is a bypass type non
bellows unit. Other t stats have been tried with similar results.
Anyone else have problems similar to this with a non-original water
pump?

Roger

Roger, '54 120 M, DHC, BRG, S678300
Tamarac, South Fla., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

I had that kind of problem on my 150 back when I was young and not quite
smart. A quick and simple test is to take the radiator cap off, then start
the engine and goose it a couple times. If you see bubbles, you have a head
gasket leak between a combustion chamber and the water jacket. That is
about the only way you are going to get enough pressure to burst hoses and
not be overheated.

You DO want to take care of this before overheating happens. I told you I
was young. I got a little smarter that day.

Gene McGough
XK-150 FHC S834515DN
XJ6C II 1976----- Original Message -----
From: “Velocette” gasssit@comcast.net
Sent: Monday, October 10, 2011 11:13 AM

I have been struggling with a problem with my 120 for quite a while.
It blows coolant overboard. It does NOT overheat, not even close.
But it has popped two upper radiator hoses, and one bypass hose at
the T stat housing.
With the engine at operating temp. (160 stat), rev the engine to
over 3500 & I can see the upper radiator hose bulging. It has blown
the top radiator hose off of the stub on the T stat housing, with
predictable results. Bypass hose is normal

Roger

Roger, '54 120 M, DHC, BRG, S678300
Tamarac, South Fla., United States

In reply to a message from Velocette sent Mon 10 Oct 2011:

Hi Roger - Are you sure the thermostat is working properly? I have
a hard time rationalizing that a pump with a 4 or 5 flute impeller
can generate enough head to rupture or displace a hose.
Considering where you live, you could replace the thermostat with
an orifice restriction in the upper hose.–
The original message included these comments:

over 3500 & I can see the upper radiator hose bulging. It has blown
the top radiator hose off of the stub on the T stat housing, with
predictable results. Bypass hose is normal
Roger


Mike Spoelker
Louisville,Kentucky, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from Mike S sent Mon 10 Oct 2011:

No headgasket leak, no overheating, not even close. Three
different t-stats, all tested ok with saucepan & thermometer.
Radiator is clean and clear (and fairly new) Tested with and
without bypass t-stat, tested with flow restrictor on bypass hose
and std t-stat (no bypass collar)
But take that stat out and no problem.

Remember folks that the t-stat is in a housing on the radiator, not
in the engine head. Thus it is subject to pressure from the pump
plus whatever pressure the system is operation at. (4psi cap)–
Roger, '54 120 M, DHC, BRG, S678300
Tamarac, South Fla., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Roger
Are you putting the T-Stat in “facing” the correct direction??
They are marked “This Side Towards Radiator”…
I know this is elementary, but stranger things have happened! As
you noted, the 120’s T-Stat goes IN the Radiator, not in an Intake
Manifold (like is common in 99.99999% of all cars built), it would
be an easy oversight…
I mention this because this is a “new” complaint from you…
(leastwise, not one I’ve heard you utter before) So, unless you have
been suffering in silence, something changed…
Charles #677556.----- Original Message -----
From: “Velocette”

No headgasket leak, no overheating, not even close. Three
different t-stats, all tested ok with saucepan & thermometer.
Radiator is clean and clear (and fairly new) Tested with and
without bypass t-stat, tested with flow restrictor on bypass hose
and std t-stat (no bypass collar)
But take that stat out and no problem.

Remember folks that the t-stat is in a housing on the radiator, not
in the engine head. Thus it is subject to pressure from the pump
plus whatever pressure the system is operation at. (4psi cap)

Roger, '54 120 M, DHC, BRG, S678300
Tamarac, South Fla., United States

In reply to a message from Bishop13 sent Mon 10 Oct 2011:

Roger,

If I recall my Pumps and Blowers course some years back, the shut
off head of a centrifugal pump is pretty much limited by the
diameter of the impellor and the RPM. Thus it would be surprising
of your pump was suddenly putting out significantly more pressure
that previously unless you changed one of these parameters or else
you were significantly choking off the flow.

Accordingly, I am not comfortable with the’’ pump on steroids
explanation’’ unless you somehow changed a pulley which I seriously
doubt.

Tends to point to a flow restriction from the thermostat if
changing that changes the pressure.

Karl–
karl
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from karl sent Mon 10 Oct 2011:

Roger did you change either the bottom pulley or the water pump
pulley when you changed pumps?–
The original message included these comments:

explanation’’ unless you somehow changed a pulley which I seriously
doubt.


Mike Spoelker
Louisville,Kentucky, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Roger,

I had the same problem with my MK1, back when it was just a used car. Do me
a favor, pull out your spark plugs and see if one of them is cleaner than
the rest.

Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2----- Original Message -----

I had that kind of problem on my 150 back when I was young and not quite
smart. A quick and simple test is to take the radiator cap off, then start
the engine and goose it a couple times. If you see bubbles, you have a
head gasket leak between a combustion chamber and the water jacket. That
is about the only way you are going to get enough pressure to burst hoses
and not be overheated.

Gene McGough
XK-150 FHC S834515DN
XJ6C II 1976

I have been struggling with a problem with my 120 for quite a while.
It blows coolant overboard. It does NOT overheat, not even close.
But it has popped two upper radiator hoses, and one bypass hose at
the T stat housing.
With the engine at operating temp. (160 stat), rev the engine to
over 3500 & I can see the upper radiator hose bulging. It has blown
the top radiator hose off of the stub on the T stat housing, with
predictable results. Bypass hose is normal

Roger

Hi Roger, just read this old post concerning your 120 blowing coolant hoses - I’m having similar issues with my 140 (see the active xk140 cooling system woes thread). I appreciate it was a while back, but was it just the thermostat that was the problem for you or was there another cause? Many thanks, Jon.