Laguna engine temperature gauge reading low

Newbie Joined: 12 Oct 2005 Posts: 2

Hi All,
I've got a Renault RT 2Litre Petrol Estate (P-Plate - with Air-Con) and for a while now, the engine temperature gauge has been reading low (in fact hardly moves off the bottom of the scale unless I get stuck in traffic). The thermostat seems to be working fine as the top radiator hose gets pretty warm while the bottom one stays almost cold until I let it idle at standstill in which case the gauge starts to move up to about the half way mark and the bottom hose starts to warm up proving coolant flow through the radiator. Temperature of warm air out of the heater also feels normal too so don't suspect a cooling system problem - at least I hope not! I got a new sender from the dealer but haven't fitted it yet because I wasn't sure if the sender (which is a push fit into the thermostat housing - held in by a clip) goes into actual coolant meaning I 'd have to part drain the system first. On top of that, I've measured the resistance of the sender when it's dunked in a bowl of almost boiling water and it's similar to the resistance of the sender on the car when the engine's warmed up. The same gauge also displays oil level for the first minute or so after the ignition is turned on and that looks fine so don't suspect the gauge itself. I'm wondering if it's the regulated voltage that is fed down from the instrument panel via the gauge to the temperature sender that's low but I've nothing to compare with. I wondered if anyone else has seen a similar problem or could measure the voltage for me on a car who's gauge reads correctly and let me know what they see. The connector onto the sender is a 3-pin green push on job so easy enough to whip off and measure across the two relevant contacts. I get a shade under 6v on mine. I don't fancy diving into the instrument panel unless I really have to and certainly don't want to pay the inflated prices a Renault dealer would charge to diagnose and fix the problem.
Any suggestions (clean ones!) welcome.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

the sender is in coolant and if you swap it quickly theres no need to mess around with coolant draining.

i say you have a thermostat issue.

The top hose should not be warm until the stat open, which should be around halfway on the gauge.

Diesels are also far more thermally efficient than petrol engiens so it will really need to be driven to get any sort of decent temp up, which won;t happen if the stats faulty.

I say thermostat. Whioch is in the plastic housing where the top hose flange bolts to it, its 3 T30 screws btw.

Newbie Joined: 12 Oct 2005 Posts: 2

Chris H wrote:

The top hose should not be warm until the stat open, which should be around halfway on the gauge.

Hmm - I take your point but surely if the stat was stuck open or even partly open there would be coolant flow through the rad and the bottom hose would be warm too? I assumed that the warmth of the top hose was caused by heat conduction across the stat rather than coolant flow through it.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

not when its cooled by passign through the rad.

Spammer Joined: 27 Jul 2004 Posts: 5717

interesting ,somehow i seem to have the same problem with my brand feckin new stat