Heater desperation

Ok, I know there have been many threads before about this, but wearing Damart clothing in my defender is losing its appeal.
The engine started to overheat (95 300 tdi).
Rad was cold in places so was replaced. Thermostat and 3 way bleeder also at the same time
Still ran hot, worse after about 10 miles or over 50mph.
Header tank pressurising. Tried running with no cap as an experiment, did not overheat so dramatically .
However still not right so pulled the head off. No visible cracks or bad warping. Replaced with a composite type gasket.
Relaced the heater matrix as it had cracked at the pipes . this is the plastic type with both pipes at the top.
Still no improvement in heater output. Both heater pipes are hot yet it blows only very tepid air.
The flaps in the box look ok.
Im running out of ideas. Can /do water pumps fail without leaking? Or is the head possibly cracked internally.
Any advice would be most welcome!

You should be able to tell if the water pump is working. Have you tested the thermostat is opening at the right temp?
If it's overheating then there's a lack of flow or an air lock. If heater pipes are hot but only tepid air, sounds like a symptom of the above

jim the sweep said:

Ok, I know there have been many threads before about this, but wearing Damart clothing in my defender is losing its appeal.
The engine started to overheat (95 300 tdi).
Rad was cold in places so was replaced. Thermostat and 3 way bleeder also at the same time
Still ran hot, worse after about 10 miles or over 50mph.
Header tank pressurising. Tried running with no cap as an experiment, did not overheat so dramatically .
However still not right so pulled the head off. No visible cracks or bad warping. Replaced with a composite type gasket.
Relaced the heater matrix as it had cracked at the pipes . this is the plastic type with both pipes at the top.
Still no improvement in heater output. Both heater pipes are hot yet it blows only very tepid air.
The flaps in the box look ok.
Im running out of ideas. Can /do water pumps fail without leaking? Or is the head possibly cracked internally.
Any advice would be most welcome!

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Are you sure you have got all the air out of the system after the various works?

These systems can be very difficult to bleed.

Found that with the Defender tdi engines parking with the front end up hill and having the plug on the rad itself out will get the air to clear the heater matrix.
As well as working thermostat [ I know you have new but there are rubbish replacements out there] having the foam seals in the heater box and the one to the bulkhead in good order make a big difference.

tottot said:

Found that with the Defender tdi engines parking with the front end up hill and having the plug on the rad itself out will get the air to clear the heater matrix.
As well as working thermostat [ I know you have new but there are rubbish replacements out there] having the foam seals in the heater box and the one to the bulkhead in good order make a big difference.

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I filled the system slowly via one of the heater hoses until coolant came out of the matrix. Not expecting volvo heater standards, but this has gone from ok ish to useless. Would a waterpump impellor problem be a possibility? Doesnt look genuine,ive had the vehicle for 8 yrs. Maintenance before that was unknown.

jim the sweep said:

I filled the system slowly via one of the heater hoses until coolant came out of the matrix. Not expecting volvo heater standards, but this has gone from ok ish to useless. Would a waterpump impellor problem be a possibility? Doesnt look genuine,ive had the vehicle for 8 yrs. Maintenance before that was unknown.

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Have you tried bleeding it from the plug on top of the rad, and if necessary, from the thermostat housing?

Water pump failure is almost always seen in the form of a leak from the seal in the middle of the pump. You could always take the pump off, and have a look at the impeller. As far as I know, impellers aren't sold separately, although I do not know for certain. A new pump probably doesn't cost a fortune, but I would go with the bleeding first, as it costs nothing.

Turboman said:

Have you tried bleeding it from the plug on top of the rad, and if necessary, from the thermostat housing?

Water pump failure is almost always seen in the form of a leak from the seal in the middle of the pump. You could always take the pump off, and have a look at the impeller. As far as I know, impellers aren't sold separately, although I do not know for certain. A new pump probably doesn't cost a fortune, but I would go with the bleeding first, as it costs nothing.

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may well end up changong the pump for the sake of 40 quid but expect the bolts will shear!
Ive tried bleeding both plugs.

If water pump not good would think that engine would soon get rather hot.
With an IR temperature reader you can check the temp of the heater pipes and compare with top of rad and thermostat housing. All should be something close and if so then problem has to be with the air flow through heater box and into cab. Fan working ok? they sometimes get slow as they age.

jim the sweep said:

may well end up changong the pump for the sake of 40 quid but expect the bolts will shear!
Ive tried bleeding both plugs.

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Make sure you take note of the bolt positions as some are longer

I reckon you have head gasket failure, easy enough to do on the tdis.

There is a fill/bleed procedure you should do when the system has been emptied, but once it has been ran up to temp and the stat has opened it will self bleed, the danger in doing that way is the cyl head can get very hot very quickly before the stat opens.
You can try the bleed procedure but I reckon have bigger issues.

He has already done the head gasket.

It looked ok when head was off. No obvious cracks or bad warpage and it cleaned up nicely. Agree, it does sound like a compression related problem. old gasket had staining around waterways which suggests it was weeping. Performance is normal and no excessive smoke.
I dont want to pull the head , go to the trouble of having it surface skimmed etc only to have a pressure test prove its cracked

Its a work vehicle to down time is a big problem. They only go wrong in winter, eh?

There seem to be two issues here - you need to sort the overheating first before the engine is damaged. The cooling systems on these engines are designed to cope with very hot weather, so should run coolish/take a while to warm up at this time of year. Once you have sorted the overheating and the expansion tank is not pressurising any more (and the coolant gauge is back to normal), you can have a look at the heater - which is usually pretty poor. The matrix can become blocked - you can flush it in place by removing the hoses. In addition, the seals inside the heater box often/almost always fail - this allows cool air from the fan to bypass the heater matrix. It's very easy to block off the bypass route with a bit of camping mat or similar - you will lose the ability to blow cool air in the summer, but as your vehicle has fresh air vents it shouldn't be an issue. While you have the heater off, sort out/replace the seal from the heater box to the bulkhead and around where the pipes enter the heater box. Lastly, it's pretty easy to fit a bilge blower in the wing intake to the existing heater blower - this will increase the volume of air passing over the heater matrix and hopefully getting into the cabin. You still won't have Volvo levels of heat, but it should at least defrost the screen!

jim the sweep said:

Its a work vehicle to down time is a big problem. They only go wrong in winter, eh?

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Looking at some of the other threads about Tdi heaters, you are going to be lucky to get the vehicle warm with the temperature outside barely going above freezing.
Even with the best possible heater, these vehicles lose a lot of heat in very cold weather, they leak air in numerous places, and the thin alloy skin of the body doesn't retain heat very well.

So, if you have got the overheating issue sorted, and need the vehicle for work, I would stay with the Damart thermals for the time being.

Never been sure on this one but is there a right way and a wrong way to fit heater pipes to the matrix or does it not matter?

tottot said:

Never been sure on this one but is there a right way and a wrong way to fit heater pipes to the matrix or does it not matter?

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No idea. I just replace them the way they were before, although I don't know if it matters.

I do the same, but only ask as others may not.

tottot said:

Never been sure on this one but is there a right way and a wrong way to fit heater pipes to the matrix or does it not matter?

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I never worried.. input/outlet same size & no restrictions
Universal direction.

Pressure test the cooling system, engine hot and then again cold.

tottot said:

He has already done the head gasket.

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Yes but as he may not have bled the cooling system correctly he may have done the head or head gasket in, they get very hot very quickly until the stat opens.