Welcome to our resource for MG Car Information.
Triumph TR6 - Overheating at Idle
I rebuilt a 74.5 TR6. New Radiator/Hoses/Thermostat. New everything I could think of if it had anything to do with the engine. For the next 1.5 years I drove it around Corpus Christi Texas for short trips (less than 30 miles). Then I had to move cross-country to Southern Nevada.
With much trepidation (and my wife gritting her teeth behind me in the mini van with three screaming kids and a dog and a cat) I began to drive the TR-6 from Corpus Christi Texas to Nevada. We drove about 400 miles per day at about 70 mph.
I promptly had an over heating problem after being on the road 30 minutes each day. While on the Freeway doing about 70 mph the Temperature needle holds slightly above the middle mark with the outside air temperature about 90 degrees F – not so bad (and it was relatively quiet in the TR-6 compared to the inside of the mini-van!).
After exiting the freeway and hitting city stop & go traffic the temperature would climb past the ¾ mark and about ½ way between the ¾ and ‘H’ mark. Very unnerving. After getting gas the TR-6 wouldn't start like ‘normal’ where it would ‘jump’ to life. Instead it would take about 30 seconds for the engine to slowly (but very steadily) accelerate from zero rpms up to the idle rpm. Once it got running it ran normally (but hot). Once I got back on the freeway again the wind would lower the temperature to just above the ½ mark.
Te next day when it was cold the car would jump to life. But then the overheating problem would repeat ...
We eventually made it to my brother’s place in Las Vegas (where I was to park the car for a few months). I later replaced the water pump, installed an ‘After Market’ electric fan in front of the radiator and also installed an external oil cooler (again in front of the radiator).
I then removed the whole thermostat (even though it was only 2,000 miles old) and did not install a new one.
Still overheats but slightly improved. It heats up to the ¾ mark (in a shaded garage after 30 minutes at idle with an outside air temp of about 95 degrees F). I have yet to 'drive' the car again as I want to solve this problem at idle first.
What now? Any ideas?
|Jake-I don't think you have a problem. When the air temp is 95 deg, my car will get close to the redline after a long stoplight, but goes back down when running at highway speeds. If your gauge is accurate, the 2 dots in the center is 180 deg., 3/4 is about 205 deg., and just below the redline is 210 deg. A good pressure cap and anti-freeze mixture should prevent a boil over. I would replace the thermostat as some restriction is necessary. The rough running is probably from the fuel percolating from the high temp.|
|2 quick questions 1 Do you have the radiator cowl in place The horrible cardboard thing that goes between the radiator forwards to the grill, It is a sad looking peice of limp shoe box material that is often thrown away but has such an important roll in any hot state, Secondly a crank mounted fan is perfectly capable of cooling in the hottest states, electric fans are only good if mounted behind the radiator but on the 6 it is almost impossible with the cross brace. Just check you have no gaps around the rad cowling CP|
|TR's just don't like to go slow.|
|I had a nasty overheating problem following a rebuild and did these 3 things to solve the problem when nothing else worked:|
1) There is a coolant by-pass hole about 3/8" dia. in the thermostat housing. With the TS out look straight down into the housing and you'll see it. I cut some threads and epoxied an allen screw into the one on my car. Also put a 1/8" hole in the thermostat housing so it didn't dead head, but since you've no TS....
2) Two of the studs that hold the water pump to the housing protrude into the pump volute and reduce flow. Pull the water pump, remove the two studs, cut off the excess, then replace the studs. Use teflon tape or pipe dope when you put the studs back in.
3) Stop the flow of "coolant" to the carb manifold by installing a clamp or valve. You usually won't need to heat the carbs in the desert, and it's another by-pass around the radiator.
I HAD a new cardboard radiator shroud installed during the drive cross country. I do not have it installed right now because I an troubleshooting the problem in the garage.
I agree the electric fan should not be necessary but I put it on (in front of the radiator) and reversed the flow so that it pushes air throough the radiator. It actually produces quite a good bit of air flow at 0 mph when I stick my hand behind the radiator (with the engine off of course).
I'm going away for a few days but when I come back I will try the water pump bolt shortening, the TS bypass hole plug and clamping the radiator hose to the carbs.
Do you think the hot radiator fluid made the fuel sitting in the carb so hot that it was difficult to start after getting gas?
"Do you think the hot radiator fluid made the fuel sitting in the carb so hot that it was difficult to start after getting gas?"
Could be. The fuel could have evaporated out of the bowls & fuel line, and the fuel pump could even have gassed off (vapor locked) from the hot engine compartment.
In regards to item #1 of the first post - the 1/8" hole is supposed to be in the thermostat flange, not the "housing" as stated. Some thermostats already have a small hole in the flange or valve to give a minimum flow, so it's worth a check if you run with one.
I read your posting regarding bypassing the manifold..i have noticed that after some excited driving i get a some hesitation and it runs rough for a few minutes, then seams to settle down nicely again..i was thinking some vapor lock as well..
I run DGvs.
I was thinking about bypassing the manifold as well, does this supply only serve to heat the manifold and not "cool"it?. If so, what type of valve is suggested?
The line is to heat the manifold up in cool weather to help vaporize the gasoline. I use a small ball valve - 1/2", I believe, with hose barbs on each end. It's 'off' in the summer, 'on' in the winter.
Thanks, seems like a fairly intelligent mod, especially given temps in the 90's lately.
One last question...i have two feeds..
starting from the front at the water pump
1: goes to Intake Manifold
2: a split from same line goes to the input side on the front DGV carb..passing through to the second and then back out to the manifold return hose.
I assume to start I might just block the DGV feed and leave the manifold?, or i could put the valve earlier in the feed line and control both at the same time...
I'm not at all familiar with the DGV's, but I suspect the heat is for the same thing - to prevent icing/help vaporize gas in cold weather. You may want to experiment with clamps first as an alternative to a valve or valves and see if there's any benefit from cutting off the flow. If it looks good, use a single valve 'earlier' to stop both flows.
|Sounds like you have the "DGAV" variant with the water operated choke as your front carb. You may want to consider using the manual choke off the rear carb (assuming that it is a straight forward, manual choke DGV) and dispense with the water choke if you plan in ditching the manifold lines. Another option would be to convert to the "DGEV" type electricly heated choke.|
I have DGV's, i might have described incorrectly though, the hot water line in is to the manifold adaptor and not the carbs themselves, so i think that they are there to serve the purpose of heating the intake rather then as a choke (which is manual)
i will experiment with a valve while there is still hot weather to enjoy.
This thread was discussed between 25/08/2005 and 31/08/2005
Triumph TR6 index