I have a 91 Rover 416 with the Honda single cam 16v engine.

The radiator has been suspect for ages and today I noticed the
temperature creep up more than normal and fluctuate. I was near home
and (with the heater on) kept the temp under control until I arrived
home. At no time did the gauge hit 'red' but it periodically got
closeish.

Sure enough, on inspection the long knackered radiator was visibly
losing water at the bottom and later when it had cooled I was able to
put about 1.5 litres of water in.

Before going to the bother of fitting the new rad I wanted to test it
to see if the head gasket is still sound so I removed the cap and ran
it to look for bubbles etc.

There were bubbles coming up into the expansion tank at tickover and by
giving it some revs I was able to use the accelerator to 'pump'
water out of the expansion chamber. (As you rev it, it just gently
wells up and overflows as you drop the revs it recedes - nothing
dramatic.)

Now, this looks like a head gasket problem on first glance, however
I'm wondering if this is actually not the case. My reasoning is it
might well have airlocks and the bubbles may just be air working their
way out; with the cap off and some revs on the water pump might be
causing the 'surge'.

I can't see any sign of oil in the water or emulsion of the type
I'm used to. (The water  has always had a white bubbly surface in the
expansion chamber - I've always assumed this was countless years of
Radweld and antifreeze.)

So in order to decide if it's worth bunging the new rad on I'd like
to know:

1) Can I (without spending money) perform a few basic tests to
establish if the head gasket is ok?
2) Can the water pump create enough 'push' to push water out of the
expansion chamber?
3) Can bubbles + revs pushing water out of the expansion tank simply be
the symptoms of air in the system?
4) In my simple mind if the temp gauge doesn't get to red, you
can't cook your gasket. Is this false? (I'm thinking a temp gauge
might get surrounded by an air lock and thus lie to me)

Thanks in advance.

wrote in message 
news:1119900646.284052.26920@o13g2000cwo.googlegroups.com...

>I have a 91 Rover 416 with the Honda single cam 16v engine.
>
> The radiator has been suspect for ages and today I noticed the
> temperature creep up more than normal and fluctuate. I was near home
> and (with the heater on) kept the temp under control until I arrived
> home. At no time did the gauge hit 'red' but it periodically got
> closeish.
>
> Sure enough, on inspection the long knackered radiator was visibly
> losing water at the bottom and later when it had cooled I was able to
> put about 1.5 litres of water in.
>
> Before going to the bother of fitting the new rad I wanted to test it
> to see if the head gasket is still sound so I removed the cap and ran
> it to look for bubbles etc.
>
> There were bubbles coming up into the expansion tank at tickover and by
> giving it some revs I was able to use the accelerator to 'pump'
> water out of the expansion chamber. (As you rev it, it just gently
> wells up and overflows as you drop the revs it recedes - nothing
> dramatic.)
>
> Now, this looks like a head gasket problem on first glance, however
> I'm wondering if this is actually not the case. My reasoning is it
> might well have airlocks and the bubbles may just be air working their
> way out; with the cap off and some revs on the water pump might be
> causing the 'surge'.
>
> I can't see any sign of oil in the water or emulsion of the type
> I'm used to. (The water  has always had a white bubbly surface in the
> expansion chamber - I've always assumed this was countless years of
> Radweld and antifreeze.)
>
> So in order to decide if it's worth bunging the new rad on I'd like
> to know:
>
> 1) Can I (without spending money) perform a few basic tests to
> establish if the head gasket is ok?
> 2) Can the water pump create enough 'push' to push water out of the
> expansion chamber?
> 3) Can bubbles + revs pushing water out of the expansion tank simply be
> the symptoms of air in the system?
> 4) In my simple mind if the temp gauge doesn't get to red, you
> can't cook your gasket. Is this false? (I'm thinking a temp gauge
> might get surrounded by an air lock and thus lie to me)
>
> Thanks in advance.
>


from your description it is fine, the only reliable test would be to sample 
the gas above the water and check for combustion using a block test kit.

1.  Try it and see.
2.  Yes
3.  Yes
3.  False, as you surmise, the sender is only accurate while in water.

mrcheerful

>I have a 91 Rover 416 with the Honda single cam 16v engine.
>
> The radiator has been suspect for ages and today I noticed the
> temperature creep up more than normal and fluctuate. I was near home
> and (with the heater on) kept the temp under control until I arrived
> home. At no time did the gauge hit 'red' but it periodically got
> closeish.
>
> Sure enough, on inspection the long knackered radiator was visibly
> losing water at the bottom and later when it had cooled I was able to
> put about 1.5 litres of water in.
>
> Before going to the bother of fitting the new rad I wanted to test it
> to see if the head gasket is still sound so I removed the cap and ran
> it to look for bubbles etc.
>
> There were bubbles coming up into the expansion tank at tickover and by
> giving it some revs I was able to use the accelerator to 'pump'
> water out of the expansion chamber. (As you rev it, it just gently
> wells up and overflows as you drop the revs it recedes - nothing
> dramatic.)
>
> Now, this looks like a head gasket problem on first glance, however
> I'm wondering if this is actually not the case. My reasoning is it
> might well have airlocks and the bubbles may just be air working their
> way out; with the cap off and some revs on the water pump might be
> causing the 'surge'.
>
> I can't see any sign of oil in the water or emulsion of the type
> I'm used to. (The water  has always had a white bubbly surface in the
> expansion chamber - I've always assumed this was countless years of
> Radweld and antifreeze.)


Last year I bought the same car for spares, advertised as head gasket gone. 
After a half-hour drive home I concluded that it was only overheating 'cos 
the radiator had disintegrated; it ran fine with no other symptoms!

Unless you've filled the cooling system slowly and then let it idle without 
the cap on until the fan runs then it's highly likely there is an air lock 
or several - don't forget these cars physically turn off the flow of water 
to the heater matrix so you'll need the control set to 'hot' to be able to 
purge the air properly...

Darren