(120kmh) the temperature drops. If I slow down to 100kmh it will rise back to the normal level.It started after I replaced the thermostat, I already bled the coolant twice.
Could it be a faulty thermostat?Temperature dropping at highway speed
Moderators: IMOC Moderators, IMOC Committee Members
Temperature dropping at highway speed
Whenever I drive my car at highway speed (120kmh) the temperature drops. If I slow down to 100kmh it will rise back to the normal level.
It started after I replaced the thermostat, I already bled the coolant twice. Could it be a faulty thermostat?
(120kmh) the temperature drops. If I slow down to 100kmh it will rise back to the normal level.It started after I replaced the thermostat, I already bled the coolant twice.
Could it be a faulty thermostat?-
SuperRedMR2
- Posts: 5494
- Joined: Mon May 16, 2005 8:40 pm
- Location: Wickford, Essex
Re: Temperature dropping at highway speed
Is it not something to do with the cool air at higher speed?
When I moved my number plate I got lower temperatures as it was being fed a better flow.
When I moved my number plate I got lower temperatures as it was being fed a better flow.
Re: Temperature dropping at highway speed
Did you make sure the thermostat was orientated properly with the casing? Otherwise the little bypass valve will let coolant flow which would be enough in the current temperatures for the temp to drop at higher speeds.
Either that or the'stat you put in was faulty which is not beyond the realms of possibility.
Otherwise the little bypass valve will let coolant flow which would be enough in the current temperatures for the temp to drop at higher speeds.Either that or the
'stat you put in was faulty which is not beyond the realms of possibility.Re: Temperature dropping at highway speed
jon_st205 wrote:Did you make sure the thermostat was orientated properly with the casing?
You have to align it?
Guess I found my problem.
What should I align, are there markings on the thermostat?Re: Temperature dropping at highway speed
Wouldn't have thought the wee valve would have had that much of an effect. 
The bleed hole should be aligned so it's at the top when you fit it from what I recall.
A test for the thermostat is to simply rev the engine up when stationary(and up to temp) and see if the the temp on the gauge drops. If it drops significantly and quickly the stat is stuck open.
The bleed hole should be aligned so it's at the top when you fit it from what I recall.
A test for the thermostat is to simply rev the engine up when stationary
(and up to temp) and see if the the temp on the gauge drops. If it drops significantly and quickly the stat is stuck open.-
FrankBelgium
- Posts: 52
- Joined: Mon Jan 16, 2006 8:11 pm
- Location: Willebroek Belgium
Re: Temperature dropping at highway speed
BIGBOBO wrote:jon_st205 wrote:Did you make sure the thermostat was orientated properly with the casing?
You have to align it?
Guess I found my problem.
Hey BIGBOBO, I'm also from Belgium and all the info is in the repair manual.
I got an eletronic version of the manual for the MR2 (including 4A-GE and 4A-GZE) from Mark (Lauren) a couple of years back.If you want we can arrange something so you get also a copy!
As for your question, I can't post pictures, previously I did it with google images but they completly changed the site and don't know how to do it now.
Hopefully another member will post the image!
I could see there is a minor difference between the installation of the thermostat on the 16V and the 20V.
I remember when I installed the thermostat on my BT a couple of weeks back, the repair manual was refering to align the "jiggle valve" with a bolt on the housing...but couldn't find it in the 16V repair manual... Any idea why?Let me know for the repair manual.
It is +/- 24MB big ...Cheers,
Frank
Re: Temperature dropping at highway speed
Thanks for the offer Frank but I already have those manuals 
.
The manual I have doesn't mention anything about aligning the thermostat unfortunately. But I will take it out this weekend and check it.
.The manual I have doesn't mention anything about aligning the thermostat unfortunately.
But I will take it out this weekend and check it.Re: Temperature dropping at highway speed
You'd be surprised how much coolant can flow through such a small hole Chris, but of course I'm not guaranteeing it's the problem. There is a line on the housing casting for alignment but failing that just get the valve at 12oc.
There is a line on the housing casting for alignment but failing that just get the valve at 12oc.Re: Temperature dropping at highway speed
Hi , it will 100% be the thermostat being at fault , what make is the thermostat as i have found in the past different makes cause the systems you are having . if i remember right first line parts did not work right but blue print parts did .
, it will 100% be the thermostat being at fault , what make is the thermostat as i have found in the past different makes cause the systems you are having . if i remember right first line parts did not work right but blue print parts did .-
Lauren
- IMOC Committee
- Posts: 38632
- Joined: Mon Dec 13, 2004 5:37 pm
- Location: Greater Manchester
- Contact:
Re: Temperature dropping at highway speed
Surely considering the cheapness it's a no brainer to pick up an OEM one?
2020 GR Yaris - Circuit Pack 
- Circuit Pack Re: Temperature dropping at highway speed
Lauren wrote:Surely considering the cheapness it's a no brainer to pick up an OEM one?
Toyota ones are knocking on
£25 but I tend to go with them these days as the ones my local motor factors supply (QH brand) are utter bobbins and I've not had one last more than 18 months. 
Re: Temperature dropping at highway speed
Replaced with a genuine toyota thermostat (90916-03046) and the problem is now fixed.
(90916-03046) and the problem is now fixed.