Kgkev

I have a 1995 Laguna 2.0L

Every couple of weeks it chucks all its water out and over heats.

Filling it back up solves it for a few weeks.

I have just refilled it for the 4th time with summer coolant and RadWeld (first time I have added anything but water)

I have just run it to make sure the fan was working and the needle got just over half way up and then the fan kicked in. The needle fell and the fan turned off - so everything OK there.

My question

Would a small leak in a hose or the rad cause the coolant to boil and run out? Or am I looking at a more serious problem?

Do you recon the rad weld will fix it?

PeckerWood

You can have a pressure test run on the cooling system to see where it leaks.

How old is the radiator cap and the thermostat ?

qldit

Good Morning Kgkev, your description may well suggest there is a head gasket pressure leakage problem.
What commonly happens is that the cylinder head (which is generally aluminium) is retained to the engine block by steel bolts, now there is an expansion difference between the steel bolts and the aluminium, so when an engine overheates for any reason the difference is absorbed by the poor old head gasket.

Although head gaskets can absorb one of maybe two overheat conditions it creates a worse situation if it keeps repeating, high pressure cylinder gases begin to escape into the water galleries and displace coolant in the system.

This usually promotes a further and more frequent overheating situation and virtually continuous loss of coolant one way or another.
This can continue for a period before the gas leakage path actually "blows" a section of the head gasket away and then coolant can enter the cylinders after shutdown and contaminate the engine oil by leakage past the piston rings.

Any vehicle that needs more than a quart of coolant a month to be added needs to be watched.

Often the gas embolisms in the water galleries in a running engine promote localised heating accentuate the problem.

Running the vehicle at a constant fast idle for a period, like ten minutes, with the radiator cap removed and ensuring the radiator is completely filled and carefully watching for "glubs" of gas bubbles is a pretty good test. Some coolant may be lost doing this. Reducing the fast idle speed whilst doing this should be avoided, keep it constant.

When coolant leakage gets quite bad, if it is leaking into the cylinder/s a further ungood situation can happen where a pool of water sitting on top of a piston may be present and if the engine were cranked in this condition can cause other damage such as bent conroditis.

If this describes your problem I would suggest worrying about it and expect to have to remove the cylinder head and obtain a new head gasket overhaul set.
Any time an alluminium cylinder head is removed they generally need a machine shop inspection and resurfacing to be "dead flat" because aluminium in bulk (as in a cylinder head) has an incredible tendency to warp when subjected to thermal cycling.

Many modern engines also require all the cylinder head retaining bolts to be replaced when the head is refitted, this is because the stresses created in the old ones can cause bolt failure and recreate the original problem.

I would doubt that rad-weld will have much effect.

When any work like this is carried out on your machine it is a very good idea to have the radiator pressure back-flushed and examined at the same time. (a very good idea!!)

Others will have different ideas.

Of course I may be wrong.

Cheers, qldit.

Kgkev

Thanks for the answers - If it loses its water again I will definatly look at replacing the Head Gasket - According to the Haynes Manual it should be quite an easy job and in expensive.

Pressure back- flush the radiator? - sounds technical. Is this something I can do with a hose and some radiator flushing chemicals?

Can I check if water is getting in through the gasket? Is that when you get white scummy marks around the oil cap?


Going back to the first poster - as far as I know both are orignals - so 12 years old.

qldit

Good Afternoon Kgkev, with regard to the "scummy" emulsion on the oil cap, generally these days the oil operating temp is sufficient to allow moisture to become part of the crankcase gas system and is vented, via the pcv system or whatever, so there should not really be emulsion evidence on the cap. Circumstantially that is a consideration pointing to possible excessive moisture in the oil system.

As engines age, it is quite common for the aluminium cylinder head to decompose gradually, often through dis-similar metal reaction and electrolysis kinds of reasons.
Radiator coolant normally contains a high level of corrosion inhibitor, but naturally the thermal cycling of any engine from day to day does accellerate corosive conditions.

Over time particles of solid aluminium salts migrate to the top of the radiator and commonly may lodge in the fine waterways, and naturally the crystalline nature keeps growing and often causes restricted flow through the radiator. Often promoting overheating and accellerating the entire activity.

When a radiator is affected severely the best method is to remove the top and bottom tanks and run fine rods through the waterways and actually poke the obstructions out, then replace the tanks on the radiator.
That is the best method when a situation is really bad, but a lesser involved and quite useful alternate method is to remove the radiator and lay it down and using a suitable adapter, completely fill the radiator with water and then give it a shot of high-flow rate compressed air, (workshop air) in the bottom, such that the hydraulic forces generated in the water has a blasting effect from the bottom and if this is done several times it also removes a large amount of any blockages.

Some people simply use a garden hose but it is not very effective.

Now if you can see any of this "gravelly" looking material in the top of your radiator waterways, the question becomes how much is apparent and this is a reflection of the probable corrosion that has happened inside the cylinder head.

Although most vehicles do have thermostat housings and other items that can sometimes be considered as sacrificial anodes or whatever, from my experience it is common to remove an aluminium head and find areas around waterways in the head severely corroded.

Most often I just get these kinds of corroded heads re-welded (aluminium) where necessary and then re-surfaced as part of the repair.
Any other tests and valve repairs are also on a condition basis.

The valve-stem oils seals are also another consideration, the answers to how far to go with head overhauling also needs consideration, valve stem / guide wear, valve seats, and the actual valves figure in this, plus the work the motor is required to do generally and the financial aspects etc.

Essentially, dependent on the vehicle and it's application, I work to keep expenses sensible, you can spend a lot of money playing with cylinder heads, but it may well be money well spent dependent on the vehicle use.

The other thing is that the expense of gaskets and other items like belts or timing chain are often smart to be replaced when doing these kinds of jobs.

If head bolts must be replaced (use once type bolts) this is another consideration.
These can be in the order of $6 each.

As was previously mentioned by PeckkerWood, a system pressure test would be an excellent idea before you get too involved.

With a system pressure test an adapter fits in place of the radiator cap with the system full of coolant, air pressure is introduced usually with a small hand pump, if any hoses or odd leaks are present they usually become immediately apparent.

Another thing that could possibly cause your symptom is a defective thermostat or one that occasionally hangs up, but this is pretty rare from my experience, if you wanted to check, you could remove it and place it in a saucepan of hot water and observe it opens before the water boils, you can use a pair of longnose pliers and place it cold water and keep repeating the exercise.
These things function by a wax type substance in a contained capsule which simply expands and opens the window proportionally to the design temp modulating the system temperature by water flow when installed.

As you mention it does not appear as a really difficult job to remove, repair and refit a cylinder head, but there are quite a few considerations needed and if it is an overhead cam type engine, other timing considerations are needed.

In view of your noted repeated overheating cycles I would suspect you will probably need to learn this procedure, but do any preliminary checks religiously beforehand.

A cylinder head needs a special procedure to tighten, using a torque wrench in a specific tightening order and many modern tightening procedures have been revised and no longer follow the information in the Haynes manuals.
This different information is included on the replacement cylinder head gasket packet.

We can probably walk you through the process if you need it.

I think I have covered most things you may need to know.

Cost your parts beforehand and checkout cylinder head overhaul and repair places, it is often more cost effective for them to supply all the parts you may require.

Others will have different ideas.

Cheers, qldit.

Kgkev

All that work a new car sounds more economical!!

I'll look at a pressure test and testing the thermostat first - Obviously start at the cheapest and work my way up.

I'll let you know how I get on.


Either that or I'll keep a load of water in the boot (trunk) and run it until the engine ceases - then sell it on Ebay for spares!!!

qldit

Good Morning Kgkev, actually the work is not all that hard, but it is "get it right first time" kind of work! (if you know what I mean! LOL!!)

Sometimes these kind of problems go on for years provided the the water is topped up every day, it probably depends on your religion!

Now in my own case it would probably die tomorrow!!! LOL!!

Best of luck.

Cheers, qldit.

boost202

Thanks for the answers - If it loses its water again I will definatly look at replacing the Head Gasket - According to the Haynes Manual it should be quite an easy job and in expensive.

Do do it right though. Have the head pressure tested by a pro, get it skimmed to so it will sit on the block flush with the new gasket. Replace the headbolts while your at it even if they say re use them. You dont want to do it again over some headbolts.