maestro TDI heater.again !

[wemyss]

Having had my Maestro TD from new in 1993 I finally handed it over to my son in law. Its still working hard travelling 70 miles per night as it takes him to his work as a tanker driver on regular night shifts.
He loves the car and it gives him brilliant MPG. Had very little to do apart from normal maintenance but in the last few months the old Maestro /Montego problem has come up.
The heater is simply only just working and gives out only luke warm temperatures which as you can imagine at this time of the year and particularly in the last week or two he returns absolutely frozen through.
Before I gave it to him I had the cylinder head gasket replaced as it was giving the rock hard bottom hose symptoms as described many times on this forum.
I also changed the cambelt as a precautionary measure and it was in fine condition with only 90 K on the clock. The antifreeze by the way was changed every year from new.
I did a search on the forum although I have read many times in the past contributors on this subject.
I even printed off (ETV) Dans excellent post on matters pertaining to heater problems and John bought the motor over the other day hoping to solve the problem following Dan’s guide.
Excuse the long post by the way….
Before doing anything I checked how well the heater was performing myself. When he arrived the temperature gauge showed its normal halfway position.
The heater steel pipe on the bulkhead was quite hot. The heater performance was dismal.
However revving the engine quite high whilst stationary made a significant improvement
Firstly check the linkage under the dash and made a slight adjustment.
Noting what has been said regarding the fragility of the pipes going through the bulkhead I opted to disconnect at the thermostat heater pipe and the oil cooler for the return.
Connecting a hose I expected to find the matrix blocked. However we got a full bore blast through it from both directions which dispelled that theory.
I thought about the thermostat but dropped that idea eventually. Now I was once a Plumber and heating Engineer before so am very familiar with heat exchangers so what puzzled me was the following. After refilling we road tested and the engine came up to temperature normally with the gauge showing its normal halfway. The bulkhead steel pipe was red hot. The return coming out of the matrix was much cooler. This shows that heat exchange is taking place but its certainly not coming out of the heater. I suppose that a full flow of water going through the matrix doesn’t totally eliminate the possibility of blockage but the fact that heat exchange is taking place makes it unlikely.
And why does revving the engine hard improve the heater.
Any help please.
wemyss

[E_T_V]

I would persevere with flushing and reverse flushing the heater matrix as the flow does get restricted through it (and also the coolant rail on the back of the inlet manifold).

If you take the rubber pipes off at the bulkhead you can alternatly connect a hose to each one and run until it runs clear then repeat in the opposite direction.

[oseerees]

I agree backflush both outlet and inlet pipes but if water is flowing and not full of crap probably not the matrix at all.

If revving the engine improves heat it could point to water pump is not as efficient as it should be at normal engine revolutions.

Check belts are fully tensioned.

I'd change the pump if belt fine?

[wemyss]

Thans for your replies. We flushed in both directions for quite a while and the water came through absolutely full bore so I feel the matrix should be OK.
The thermostat seems to be operating normally so I would rule that one out.
We thought about the water pump not operating efficiently but wouldnt that affect the cooling it this was the case?.
The cam belt was changed only a year or so before I handed it over to John.
ETV mentions in his post on heaters that the head gasket can affect the heater.
Would you explain how this would stop the heater from working Dan. I have this awful suspicion that this could be the only remaining explanation left.
As mentioned in my earlier post there is a definite heat exchange from where the flow goes in to the bulkhead en-route through the matrix to its outlet.
I can only surmise that there is insufficient flow in operating mode to make the heater work efficiently.

regards
wemyss

[E_T_V]

When the headgasket fails bubbles of combustion gas enter the cooling system. These bubbles usually end up collecting in the heater matrix (one of the highest points), and so the heater performance goes downhill as there is little coolant flowing through it.

[G Force]

The thermostat seems to be operating normally so I would rule that one out.

ETV mentions in his post on heaters that the head gasket can affect the heater. I have this awful suspicion that this could be the only remaining explanation left.


I understand your reasons for assuming the thermostat is working ok, but try to get hold of and fit an 88 degrees centigrade Bypass blanking thermostat before condemming the head gasket. It should improve the heater because it is a higher temperature over the standard 82C and if the old one is sticking open when it should be closing it will improve the heater performance significantly.;)

[wemyss]

Thanks G Force. Will have another go at checking for blockages and then go down the route of finding the higher opening stat.
John was on the phone last night to tell me that he has got a deadly cold virus as a result of having no heater.
Wanted to know how long the warranty on the car was for. Told him he was unfortunate as it had just ran out and as I had given it to him free gratis his chances of legal redress were pretty slim.
Joking apart he was going down the motor shop today to get one of those electic heater fans which plug in to the cigar lighter. I can understand his predicament after driving through the night in his heated cab and then at 3.00am climbing into the Maestro covered in ice to drive for an hour home with no heater. I also can't resist mentioning to him that he trained in Norway for Arctic warfare in the Marines and a little bit of our bad weather should mean nothing. He used some French words which I didn't understand.

wemyss

[G Force]

Hi again, In this cold climate it would not do any harm to blank off half of the main radiator with something suitable just as a temperary measure until you find the cause of the problem. This should improve the heater without causing any damage to the engine this time of year. A little crude for these reletively modern times I know, but screening off the radiator was quite the norm 40 / 50 years ago.;)

[Simon]

If the foam surrounding the heater matrix is worn thin and threadbare then this will let cold air by-pass into the car and spoil the heater's performance. Replacement matrixes (Matrices?) do not come with any foam attached at all.

[wemyss]

Thanks SImon..Yes I have heard of this one a previous site. I must say that I have never seen the heater matrix as I'm not agile enough to crawl under there and my lad is too big.
Just exactly how would this give poor heater performance?. Would the fan draw cold air from under the bonnet and by-pass the matrix.
On Monday we stripped every water pipe to ensure there was no obstruction. Even past the oil cooler and in to the bottom hose. The matrix and all the pipes takes a full bore hose flow through everything, so it is definitely not this.
The thermostat works as one would expect. Cold top hose until it eventually opens. Johns mate who was a mechanic had the car once before and he tried to remove the thermosat but the stud was seized and he only managed to take the corners off the bolt.
I was not going to attempt to remove it myself as he needs the car for work and I didnt fancy the bolt snapping off. But I think its going down the wrong trail anyway.
Advice in plenty from their drivers mess room and one lad came up with how he once had a new Maestro diesel van.
He said he was having similar problems to John. Under warranty took it back to the main dealer who (according to him) said it was a well known problem and the answer was to fill the matrix from the out side of it to eliminate a air lock.
Took it with a pinch of salt and filled it with the hose from the return but it made no difference.
As a one time Plumber my own theory goes something like this.
The steel pipe along the bulkhead into the matrix is red hot. The return coming out is luke warm which shows an heat exchange is taking place exactly as in a domestic radiator.
However what we don't know is the flow rate through this pipe.
If it was insufficient it would give the same symptons as we are experiencing.
Given that the pipes are clear I can only assume that the water pump is not delivering sufficient flow.
How could this be I dont know as I presume its only an impellor and if it had broken off we would know about it in other ways.
So Simon your theory may be the one but where is the heat going?
AS G Force suggested I have advised John to blank off part of the rad the same as we used to do in the past. My first car a Moggie had a really posh leather one whith little panels you could roll up.
regards
wemyss

[G Force]

Hi does the cab get warmer if you manually close all the face vents and set the control to screen + feet.? I think that screen + feet is available but it is a while since I sat in a Maestro.:(

[021 475 2101]

Thats deffo an air lock of some form. So try this....

Find and old fiat tipo / Uno in the breakers thats got an inline bleed valve on its heater pipework.

Fit into the Monstro's top heater pipe at the bulkhead - same hose diameter

Run the car up to temp

Turn heater onto hot (make sure flap rods are fully over)

Run engine and turn fan to pos 2 & direction flap to screeen

Slowly loosen bleed screw a few turns and run engine at a fast idle till the fizzes and gurgles from the open valve change to constant coolant.

This did the trick on my old monty estate, if this fails you may be looking ata corroded water pump or the dreaded blown head gasket between cyls 1 & 2

[1100man]

Hi
I had exactly the same symptoms with the old engine in my TD montego. Heater luke warm got better when engine revved. I tried everything; checked flow, temperatures, thermostat, heater matrix & suspected water pump.Eventually took head off to investigate high water consumption and found most of the small water holes in the head gasket blocked with strands of silicon gasket sealer! Replaced head. Heater infinitly better (water consumption still about a gallon a day due to cracked head!!) I do find with all the td's that it takes about 10 miles to generate enough heat in the engine to get a reasonable temp from the heater

[Rich]

I can understand the situation completly. I have a TD van, which has been giving me heater woes for, erm, a long time. I have now managed to get a reasonable output from the heater, but it takes a very long time to make a noticable difference in the cab.

Firstly foam seals, where the "M" heater unit issues cold air from the face vents, a foam seal to any of these will cause an air loss, and result in cold air leaking behind the dash. Also, around the matrix itself are foam seals, which ensure the air is pumped through the matrix, rather than around it. The latter rarely fails unless the matrix has or is leaking, or you remove the matrix and it all pulls it all off.

The cold air leak can be detected by putting your hand up the side of the glove box, and up the side of the cigar lighter area and feeling for air leaks. The other way to tell is to put the heater to screen, and have the fan on I with all the face vents closed, you should be getting a respectable amount of air from here, if its weak or feeble, suspect a tired fan motor, or an air leak.

Saying that, the foam seals usually only get damaged if the dash has been in and out, I replaced all of mine following a burst set of pipes, then matrix, honestly in the last couple of months that dash has been out so many times! The replacements improved the air flow, and gave a new heater smell for a while.

But I still have the same problem as you, which is the feed pipe is red hot, the return is stone cold. I am pretty darn sure there is no air in there, and the stat is good 88 degree, and quite new. The water pump is new, and the HG was done about 15k ago. I think it could now be one of the following, a corroded feed pipe (the one that runs across the manifolds) resulting in a poor flow, or a blocked oil cooler, again producing the same result. I would suspect the heater pipes were corroded, but I fitted a set which were very good, so I can dismiss this.

My next plan is to replace the feed pipe with a copper pipe, and the bypass the oil cooler, and see what this does. The only other thing I have thought of, which worked on a N/A diesel van, was replacing the header tank cap. The old one was tired, and must have been letting pressure out, a new one made quite a difference.

Will let you know how I get on, but in the mean time, don't give up!

[wemyss]

Thanks for all the replies and suggestions. Some of them have already been tried and others are new.
The oil cooler has been checked simply by putting an hosepipe through.
The steel bulkhead pipe has been removed and is completely clear.
The dash has never been out so hopefully the foam is still intact.
Having changed the anti-freeze annually all its life with 50-50 glycol based has kept corrosion and blockages at bay.
Like Rich I don't believe its an air lock. All the times I have changed the ant-freeze it has always been a good easy filller in contrast to some cars. Similar to some heatiing systems you get good ones or badly designed ones which can be pigs to get a good fill. Why would it suddenly change. And we did fill the matrix with the hosepipe hrough its bottom connection and bled through before filling.
The rad cap is a good one as of course it would be then running at lower pressure meaning lower temperature. Will try a new one.
John bought a plug in heater off e-bay which gave a little light relief inasmuch it gave us a good laugh. If you hold it close to your face you can just feel the warmth. Not recommended...

wemyss

[norbert eggcup]

there is one other thing to try which i did with a mates metro years ago- the cable for hot/cold flap just needed adjusting as it was still allowing cold air to mix whilst in hot setting irrc you can do it on a monstro from the footwell