SD1 heater

[DaveEFI]

The heater on my SD1 has always been slow to get going - even when the car was near new. On my BMW 528 with an all ally engine, and a cooling system capacity not much different, the heater starts producing heat within about 1/4 mile from a cold start. On the SD1, it's more like 1.5 miles.
Interesting one is a mate's Range Rover - with a Rover V8 - produces heat very much quicker.

Now there seem to be as many methods of just where the heater feeds are picked up on the RV8 as I've had hot dinners. My SD1 has that horrid steel pipe running under the inlet manifold - later engines dispense with this. I'm intending fitting the later manifold when I do an engine re-build later this year - if only to get rid of that pipe.

So is it the later serpentine engine with different water pump which makes the heater work sooner - or something else? Would an electric pump be an easy answer?

[DEVONMAN]

Have you asked other SD1 owners if their heater is the same?
It could be that the heater design is not that good or maybe the matrix is clogged. Is there a control valve on the system? If so, is it correctly adjusted and not bunged up.

Regards Denis

[DaveEFI]

Have you asked other SD1 owners if their heater is the same?
It could be that the heater design is not that good or maybe the matrix is clogged. Is there a control valve on the system? If so, is it correctly adjusted and not bunged up.

Regards Denis

Trouble is that very very few SD1 owners knew the cars when new. I did as I've owned mine from 2 years old. Many say the heaters are rubbish - which isn't true. They may well be now - when blocked after the years. The only valve on mine is a water stop type for when the AC is on.

As I said, it has always been slow to get going. The later Range Rover, not.
I wondered why.

[DEVONMAN]

If there is a valve on the heater feed then it's likely there is another route for coolant to circulate when the stat is closed. Effectively a bypass system that does not go through the heater matrix. Has your system got a bypass hose running into the back of the water pump housing as well as the return from the heater into the bottom hose stub.
I don't think the later serp counter clockwise pumps are better than earlier pumps but the external thermostat thingy does control / close the bypass system more effectively when the thermostat is open.

Later engines run a bit leaner and they may well heat up quicker as a result.

I have an SD1 3500 heater if you ever need it. I took it from a 1982 vanden Plas in 1992 and kept it in my loft. Don't know why.

[ChrisJC]

I think there are two ways of doing it:
- Thermostat bypass circuit is also the heater circuit. Therefore the heater matrix always gets hot. You need a flap in the heater box to give you hot / cold. My P38 Range Rover is like this and it gets hot very quickly.
- Thermostat bypass and heater circuits are different. The heater circuit can be shut off to get cold air. No need for a hot / cold flap in the heater box. This means some of the hot water will bypass the heater as the engine warms up. My Landie is like this, and it takes longer to warm up the heater than the Range Rover.

Also, don't forget there are legislative requirements on warmup time for modern cars (hence the Diesel pre-heaters fitted to some Diesel cars!), with engine management systems doing all sorts of tricks to get the cats warmed up ASAP.

Chris.

[DaveEFI]

The SD1 has an air blend heater - same as the P6 before it. There is an on off valve for the water flow - but only to shut it off fully when the AC is on.

Once the engine is fully up to temperature and the thermostat open, the heater is fine. Which does suggest it may be to do with the bypass arrangement. Gawd knows there are enough variations.

[ChrisJC]

If the SD1 heater circuit is always open (jerry-rig the AC part of it), then you could try clamping off the usual thermostat bypass so all the water goes through the heater until the 'stat opens.

Chris.