Thread: 82° Thermostat in a 4L V8

Originally Posted by walker

Well I don't know what's going on with mine. I installed the new 82 thermostat and running temps went up. From about 95 up to 104. I assumed I had a faulty thermostat and so had it swapped for another. But again I had running temp of 103!!!
So I have no idea what's going on. It was a Bearmach thermostat not original but I doubt both would be faulty.

I had the same problem,
I purchased PEL500110 - 82° With Light Spring & put it in my TD5 Disco, my temps went up to 96-99+ deg on the diagnostic.
put the old thermostat back and it now runs low 90's up to 96 deg.
I think the softer spring by-passes to much coolant on the higher RPM's???
Rave does state the thermostat doesn't fully open until 96deg tho

Im happier seeing the lower temps at cruising!!

According to Des Hammill (How to power tune Rover V8 engines for road and track), LR increased the engine operating temperature to 96*C in GEMS managed engines (1995 onwards) to meet more stringent emission requirements. Due to this increase, coupled with two other compounding factors (Range Rover cooling system layout & the practice of cherrypicking the better cast blocks for the 4.6L engine), a large proportion of 4.0 blocks are alleged to suffer from cracked block / slipped liner problems.

One of the specialist UK based Rover V8 engine builders (Wildcat Engineering), overcame the cracked block problem by using flanged / top hat liners, which has become the pseudo rebuild standard. Others on the other hand, such as John Eales / JE Engineering, never found it to be an issue in their race engines which run much lower temperatures (typically 60 to 80*C) while under considerably more stress.

I'll be sourcing a 74 degree thermostat (P/N ETC4761) for my EFI V8 to minimise the chance of a slipped liner, as well as to get more power out of the engine. (An engine running at 100*C makes approx 10% less power than an engine running at 80*C.) I'll also be drilling several small holes in the thermostat flange for self bleeding.

HTH

Bojan

I think its overstated. British Offroad say the rover v8 including in the d2 is pretty bulletproof. A mate of mine with a 4.0 2003 mistreated his terribly and never serviced it much. Ran the oil to the oil light several times and kept going. Blew oil pump off and drove for over a min with it at zero pressure. New pump on. Kept abusing and at 140k it lost oil pressure and got very noisy. Crank had lost all its hardening and it had lost most compression....But no problems with liners.

Mine got to 200k with 2 bad overheats that werw my fault. Stripped down due to blown head gasket. Liners excellent and put back together British offroad have many such stories.

I know some liners slip but there is a high percentage that dont acedotally. Head gasket failure from cooling system lack of service or like me cross threading a header tank cap is more common.

Cheers

He quotes that 80% of 4.0L blocks will suffer block cracking problems during their lifetime, and have the capacity for approximately 3 overheats. I agree that it seems somewhat overstated, however how would I judge?

Basing an opinion on my own experience would be basing on a sample of 1. If I had access to the Land Rover claims department data, or perhaps even a Rover engine rebuilder, I might be in a better position to estimate. In absence of more reliable data, I'll have to use theirs.

With regard to running low oil pressures - cross bolted blocks have proven to be able to withstand some neglect / abuse in this regard but lack of lubrication is not really related to liner failures.

I know what your saying mate. I am heartened by British Offroad's experience - large wreckers and motor rebuilders of TD and V8.

Cheers

Hi
Just an update.
The part number PEM101020 is no longer available from rimmers, it is replaced by PEM101021 and is listed as a 87 deg for an MG.

I had to replace mine because recently upgraded to 4.6HC and they threw out old thermostat.

Temps are running the same 85 to 90 in traffic.

Mine are 90-96 in traffic and 88-90 on open road. 251,000K now. Stock thermostat. No liner shift despite towing heavy loads in summer in QLD and (through my own negligence) overheating the engine and blowing a head gasket because of it (not the other way around).

Cheers

looks like someone slipped off that knife edge.
lucky if it was only gaskets

mine seems to sit around 90 at 100kph with the van on,,
and around 90 without the van