My thermostat is shot (coolant not getting up to temp, oil not getting up to temp, all diagnostic readouts low).

I understand the thermostat is in a place that makes it a bit of a job to change. I'm not scared of work, but don't have the time to do it at the moment (have a 1000 sheep yet to lamb and 100 cows to calve), I also don't have time to wait for a garage to do it, plus I sort of detest incompetent "professionals" messing around with my car, leaving a crucial bolt loose, causing grief and costing too much...

 

In a previous life, many centuries ago, I owned a rover 75 diesel (actually still one of my favourite cars, the swan-song mobile) which had a similar problem with thermostats sticking open plus unreachability, as well as running relatively cool due to pretty high thermal efficiency. The easy "fix" for that was to leave the old thermostat in place and put the thermostat from a renault 5 inside the top rad hose. It fits in snug enough to not need any fixing, costs are very low, and it's a 5 minute job to do.

It worked really well, with the added benefit of opening a little hotter (it ran more efficiently, fuel-wise at higher temperatures) and cooling was never an issue seeing as cars are generally designed to cope with temps well in excess of what one might encounter in northern europe. Towing a heavy trailer up the hills in 38C, not an issue.

 

So.....,

Is there any technical reason I shouldn't do this to my trusty Scout?

By technical I mean following actual logic, not vag fanboy reasoning such as "if it was a good idea, the manufacturer would have done it"...

I know it's not a "proper" repair, but if it gets me by until I have time (or more honestly, inclination) to fix it properly I'd be happy.

 

Cheers, Daniel

Depending on what sort of driving your doing, maybe use something to cover the radiator? If you're doing a longer drive or the temp gets too high, it shouldn't be hard to remove or trim at the side of the road.

 

Obviously overcooling isn't ideal but assuming it can still perform a dpf regen, it's probably fine. I think I had a failing thermostat for about a year before I replaced it 😉

9 minutes ago, langers2k said:

Depending on what sort of driving your doing, maybe use something to cover the radiator? If you're doing a longer drive or the temp gets too high, it shouldn't be hard to remove or trim at the side of the road.

 

Obviously overcooling isn't ideal but assuming it can still perform a dpf regen, it's probably fine. I think I had a failing thermostat for about a year before I replaced it 😉

The old bit of cardboard....

It works, but not nearly as well as having a thermostat! Just limiting airflow through the rad still allows all that extra coolant to circulate, drastically increasing warm-up time. Since most engine wear occurs during the first bit of running, it's essential for longevity to reduce thee time it takes for the engine to be up to optimal operating temps. 

I believe the cooling system layout looks like this on CR engines:

 

Where:

1 - Expansion reservoir
2 - Radiator for exhaust gas re‐circulation
3 - to auxiliary heating
4 - from the auxiliary heating
5 - Cylinder block
6 - Heat exchanger of heating system
7 - Throttle valve
8 - ATF radiator
9 - Coolant regulator
10 - Engine oil cooler
11 - Coolant recirculation pump 2 -V178-
12 - Radiator
13 - Coolant temperature sender at radiator outlet -G83-
14 - 4/2 way valve with coolant regulator
15 - Coolant pump
16 - Cylinder head

 

The question in my mind is where should the inline thermostat go given the original one is a 4/2 way valve rather than just an inline thermostat?

 

I'd be concerned that an incorrectly placed inline thermostat could cause sections/components to overheat or even block the flow to/from the coolant pumps. I don't know enough about exactly how the system works to suggest a location