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Car Forum / Volvo Cars / February 2005Head Gasket 1988 740
If the head gasket has gone then one of the problems will be air will enter the cooling system. If air is entering the cooling system caused by a blown or leaking head gasket then is air is replacing the water would it first cause the heater to stop working. >If the head gasket has gone then one of the problems will be air will enter >the cooling system. >If air is entering the cooling system caused by a blown or leaking head >gasket then is air is replacing the water would it first cause the heater to >stop working. Is this a question? Stricktly speaking it is not air that pushes the water out, but combustion gases - exhaust. If the coolant level drops low enough, then the heater will stop working. IME, on a 740, this happens before the temperature needle registers anything wrong.  SignatureTSH For email, replace 'SpamOnlyToHere' with my initials "Stewart Hargrave" <SpamOnlyToHere@MiserableOldGit.Me.uk> wrote in message <snip> > Strictly speaking it is not air that pushes the water out, but > combustion gases - exhaust. If the coolant level drops low enough, > then the heater will stop working. IME, on a 740, this happens before > the temperature needle registers anything wrong. That's my experience, too - anything that causes the coolant level to drop causes the heater to stop working at idle. You will also hear gurgling noises from the heater as the engine revs until the level drops too low to pump coolant up to the heater at all. A good screening test for exhaust gasses getting into the coolant is to take the reservoir cap off when the engine is cold, start the engine and place the palm of your hand over the reservoir. If you feel pressure build in a couple of seconds, or a pulsating pressure, that is bad news. Be aware the pressure will normally build if the engine warms up much while your hand is over the reservoir - don't mistake that slow rise for exhaust leakage. Mike Will exhaust gases not act just like air if it enters the cooling system and cause an airlock. > "Stewart Hargrave" <SpamOnlyToHere@MiserableOldGit.Me.uk> wrote in message > <snip> [quoted text clipped - 15 lines] > > Mike What I found usually happens is it leaks coolant into the cylinders when it cools, drawing air in through the reservior or overflow tank to replace it. The gas blown in acts like air but shouldn't cause a lock, just rises to the top of the system until it has more air/gas than coolant - if it's leaking that fast it is likely to not start because of a cylinder full of water. There is often no evidence for where the coolant went & that loss is usually my first indicator. > Will exhaust gases not act just like air if it enters the cooling system > and cause an airlock. [quoted text clipped - 24 lines] > > > > Mike >Will exhaust gases not act just like air if it enters the cooling system >and cause an airlock. That's possibly why the heater is the first thing to stop working. But the exhaust gases will keep pushing their way into the cooling system at high pressure, and will tend to keep pushing the water out. It's not like an air bubble that simply didn't get purged when the system was filled. SignatureTSH For email, replace 'SpamOnlyToHere' with my initials >>Will exhaust gases not act just like air if it enters the cooling system >>and cause an airlock. [quoted text clipped - 4 lines] > not like an air bubble that simply didn't get purged when the system > was filled. Another thought to keep in mind is that the heater core can leak without drawing much attention. So in addition to being the high spot it can also be a leak point. When my heater core leaked 2 years ago, it was soon after being recored by a shop I trusted. (Nobody bats 1000, I guess.) I was especially concerned that the fogging vapor from it increased a lot when I accelerated hard because I was afraid that meant the boost was forcing more gasses into the system and that blew the heater in the first place. No - it was just the rpm pumping coolant into the nearly empty heater core that was doing it. I wasn't all that relieved, though; accessing the heater core is a lot of work in the 740/760. Mike If the heater core leaks where does the water end up inside or outside the car > >>Will exhaust gases not act just like air if it enters the cooling system > >>and cause an airlock. [quoted text clipped - 19 lines] > > Mike > If the heater core leaks where does the water end up inside or outside the > car Mine ended up in the carpet at the driver's feet. It leaked quite a lot before I noticed it, but if I had looked it would have been obvious long before that. Mike >Will exhaust gases not act just like air if it enters the cooling system >and cause an airlock. Either several different people, all with worries about their head gaskets on their '88 740s, have remarkably similar headers to their posts (including Posting Host, and client version), or one person keeps changing identity, and then asking the same questions again. Since last November or before, several experienced guys pointed 'Les' to his head gasket. We did the same for 'Rock', and now 'Andy' has the same symptoms. The thing is, whoever you are, we're all happy to try and help out with an honest worry; that's what this NG is for, and it's a pretty friendly group as these things go. But what you're doing is a bit rude. Changing you ID and then asking the same questions again is making a monkey out of all of us. As people realise, you will be considered a troll. Whoever you really are, we understand your concerns about needing to be sure what the problem is, but we've been as helpful as we can be several times. In the end, we can only suggest our best guess. We can't make that final decision for you - you have to consider whether we are making sense or not; you have to make that final leap of faith that it really is the head gasket and get it fixed. SignatureTSH For email, replace 'SpamOnlyToHere' with my initials > >Will exhaust gases not act just like air if it enters the cooling system > >and cause an airlock. [quoted text clipped - 3 lines] > posts (including Posting Host, and client version), or one person > keeps changing identity, and then asking the same questions again. Maybe it's the "mechanic" who buggered my nissan van a few years ago - he thought every problem originated from the head gasket. Perhaps he just wants to be sure before he does it again, the customer will wait... some are as stupid as I was. Hi. I have changed my ID from Rock to Andy Mann but not out of choice but advised that tomtom.com was a domain name which I was requested to change so decided to change also the user ID from Rock to Andy Mann. I really love my 740 Estate so does my wife and we don't want to scrap it based on cost, I have an MOT in May so depending on that cost will depend on what I do with the problem with the cooling system. I am nearly 60 and don't know how to change the head gasket that is if it is the head gasket at a cost of ?200 and then find the problem is still there and it was the heater matrix. So apologise and hope I have clarified my reasons for postings, I am going to now try the hand on the reservoir to see if there is instant pressure. > >Will exhaust gases not act just like air if it enters the cooling system > >and cause an airlock. [quoted text clipped - 25 lines] > sense or not; you have to make that final leap of faith that it really > is the head gasket and get it fixed. >Hi. > >I have changed my ID from Rock to Andy Mann but not out of choice but You can call yourself what you like on the internet - nobody has a right to know your true identity. But when several different people all post from the same computer, and all cover the same ground, it makes troll alarms ring. >advised that tomtom.com was a domain name which I was requested to change Using other people's domains is a bit naughty. If you want to obfuscate your email address completely, you could use me@privacy.net The owner of this set it up especially for people who don't want to disclose their addy on forums, and allows anybody to use it thus. Although your earlier noreply@invalid would do also. You probably realise that tom_tom.com is an impossible domain, because of the '_' in it. >I really love my 740 Estate so does my wife and we don't want to scrap it We sympathise with that. But let's recap what you have described under your various IDs: From memory: Your heater makes gurgling noises and stops working. You are losing water from the cooling system, but there is no apparent leak. The cooling system becomes pressurised, even before the water has had time to heat up. The system remains pressurised, even after the engine is long cold. There are strange smells in the header tank that might be exhaust fumes. Together, all of these point inexorably to head gasket failure. It *may* be a cracked head (unusual), or even a cracked block (very unusual), but these faults will require the same initial amount of dismantling to find out. Head gasket failure seems fairly common on older red block engines. It *may* be that you have several different problems causing some of the above symptoms, but taken together, most people will suggest head gasket. What you won't get from anyone who has any experience, is a 100% absolute guaranteed diagnosis, no matter how many different ways you describe the symptoms. SignatureTSH For email, replace 'SpamOnlyToHere' with my initials |
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