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Hallo to anyone :D

I´m living in Switzerland, owning a P38 from July 2002 now for about 2 years. (Other cars in the moment are a BMW M3 individual E36 cabrio and a tuned up Daimler Benz 420 CDI W211). My P38 is a great car, suitable for all purposes I do need and especially appropriate for our mountain area. I´m following the forum now for several months, as I´m interested in cars and engines at all and in case to require some tipps for some do-it-yourself-restauration. I must say - it is a interesting forum, giving helpful advice and I realized the members to be very cooperative to each other from my so far outstanding position.

Now I´ve got a problem I would appreciate your help - not so nice in the momentaneous climate - as the heating doesn´t work :?: . The problem occured suddenly. The car is now standing for 1 week in the garage :crybaby2: and the mechanics are looking really questioningly more and more. :think:

The control unit doesn´t show any failure function. Any other parts of the heating circulation is working properly.

We have tested the valve-motors of the ventiallation system really working - when pushing the control-buttons in the heating unit, air flows anywhere we do want and we can hear the valves working - but it is allways only cold air.

The sensor for temperature seams to be clean.

Sometimes for a moment the air becomes a little bit warmer but this effect is only momentaneous.

We checked the water flow and here seems to be a problem: the tubes coming from the engine - there is one more or less warm, the other one rather cold. We dismounted the tubes purging them with fresh water. The water passed for a moment and then the effluent was blocked. Thus we estimate that there is something blocking the circumflow in the area of the heat exchanger.

Question : We were searching the forum - I heave found one advice that indeed the heat-exchanger might be blocked. Is this reasonable, which might be caused this even suddenly occuring and how can we open the blockage ?

Question : Is there a ingoing central heating valve to the heat exchanger ? We have interviewed some technicians in the garages nearby and we have got two estimations - there is indeed such a valve and the other there is none ! What is correct ? Where is this valve located if it exists.

Can us give anyone give some helpfull ideas how to solve the problem ?

Many thanks in advance.

DS
 

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Welcome!

Have you tried flushing it by sticking a hose into the "cold" side?

Be careful with the pipes, if they are moved too much you might get a leak at the connection between the pipes and the matrix and it's not a nice job (see heater core o-ring sticky).
I haven't seen a valve anywhere while replacing my o-rings, if you want all the information how everythings works, search google for green oval and download RAVE from there.

Sigi
 

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@kmagnuss : The coolant level is ok.

let me cite from the search "If both sides are cold it is most likely that there is a problem with the water circulation through the heater matrix, or there is a air lock in that part of the coolingwater system. Feel the hoses in and out of the matrix and see if they are hot." What at all shall be a "air lock" ?

@munichp38 : We did net yet try to push something into the tubes. We just applied a strong water stream to flush in, but only from the inside. (oh yes I´m afraid of affecting the o-rings.)

what do you mean by google for "green oval and download RAVE from there" ?

DS
 

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fullspeedy said:
what do you mean by google for "green oval and download RAVE from there" ?
THat means go to GOOGLE and search for GREEN OVAL RAVE and download it. RAVE is the workshop manual for our rigs. You'll find that you can't live without it once you get the hang of how it is laid out. You will especially appreciate the electrical schmatics and locating pitcures! :thumb:
 

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Hi and welcome to the site. I'm 1/2 Swiss but born in Canada so we can appreciate having warmth inside the vehicle. As keith has pointed out a possible airlock might be a cause of your problem. When the flow of water stopped did you try to reverse the flow of water to see if anything would come from that 1st pipe. It does seem unlikely that matrix would be plugged unless someone planned it that way so that water would not leak into the cabin, which for the uninitiated, is a very expensive dealer repair. If you join the 2 hoses together under the hood then both should get hot when the antifreeze solution is circulating. If so then problem is in matrix area and not forward from there. I have never read that a valve exists in the matrix so its more likely that someone has actually blocked the flow or there is a malfunction closer to the engine/thermostat. From my manual, the antifreezee flows from hose at engine to matrix and from matrix to thermostat housing. I know that on old general motors cars the port off the engine [which supplies the heater] had a flow restrictor which could get plugged from rust and debris. Your engine seems much to new for that unless some errant strands of silicone sealant have plugged that port. Keep us posted on what you find
 

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Next experience from this morning:

The technician examined the tubes under the hood, according to your advice. There is indeed no pressure reduction valve.

Then they made a pressure test - anything was tight, no leaks detected. The test was done under cold and stopped engine condition with heating system shut down and in warm condition with heating vent switched on max in order to see a possible influence by the matrix or the thermocontroller. But there was no difference.

With running engine one tube became somewhat warm, the other one remained cold. In the cabine a slight stream of heating could be realized.

The technician then unplugged both tubes under the hood. Starting the engine pumped immediately some water trough the unplugged tube. Then he poured water into the inlet to the matrix. For some moments water was coming from the outlet of the matrix, then the flow stopped. Then he tried the opposite - same result. He detected no corossion or other mud coming out. Then he tried once more with more pressure and now the water passed through and did not stop again.

The tubes have been replugged into position and we got the same result as before. Only very slight heating. Now the system was evacuated and degassed. After this procedure the heating was really working. He tested it now two times, cooling down the car and then starting the engine again. It seems that the problem is solved now, as the heating is reacting on the control unit as it shall be. He will drive the car tonight and watch the effect until tommorow.

In the moment it looks like as if the heater matrix was filled by air, thus blocking the flow.

I will report tomorrow again.
 

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Interesting but a concern too, if air was in the system you would hear a odd sound (gurgling) have them check water pump bearings

The system usualy purges itself from air.

By the way you can turn off AC by pressing the top right button on the control panel, green light on means its off
 

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Ok some time has past - let me tell the resumee of the repair.

After the purging the heater it first nicely was heating. But only for some days - the same problem occured again. Same procedure with purging again. And then after another week we realized, that the heater was loosing water (it was clear that it was not coming from the manifold with the suspicious o-rings.) It drained the carpet on the rigt side. Following the problem, we dismounted the heater and when pressurized we saw a very thin fracture in the heater. Probably this was also the reason for the air intake. When flloding it several times under pressure we supposingly opend up the allready existing small leakage. Now the item is replaced and the heating is now working for about two weeks properly.

Best regards
 
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