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By pass hole in Thermostat?

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Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
The thermostat I installed last spring did not had a by pass hole in it, should it? Looking a the thermostats in Rimmers they all do for a 3.5 Rover. The problem I am experiencing is a fluctuating temperature gauge. On initial warm up it will go over 3/4 and then drop back to just over 1/2 then for no reason I can pin point will go back to over 3/4 and then back to near 1/2, it does this consistently as I drive. Open road or stop and go traffic seems to make no difference. Sometimes a constant cruising around 45 to 50 MPH will cause the temp to rise and if I drop to third to increase revs it will go back down. Possible radiator problem, moving more coolant?

I may have a small leak at the Ranco valve, which would cause a high reading from low coolant. The intake manifold I have does not have a sensor for the high speed fans and the carbs are manual choke. The low speed fans are connected to the ignition and the high speed fans are connected to the radiator sensor. So the high speed fans come on at the upper 190's vs the mid 220's.

Is there a connection between the temperature gauge, fuel gauge and tach? My fuel gauge is not always steady and the tach reads low. The fuel gauge probably has a weak ground some where as the intank fuel sender was replaced last summer The tach is operating off a Petronix Distributor. Last spring I cleaned the grounds from the engine to the frame and also the ground in the trunk. Is there a ground under the dash I am not aware of?



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

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darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
Hi Patrick,

The hole is to help bleed air out of the system. Having air could contribute to what you see. But there is also a known issue when the fans come on, that if the instrument cluster isn't well grounded, that will cause a high reading. The pins in the connector at the top of the instrument cluster can loose tension, or become corroded.

Also, do you have all of the original bypass hoses in place? Is it an original water pump? Some reproductions a while back where also missing a bypass hole.

Anyway, if you can correlate the fluctuations to the radiator fans cycling on and off, I would start with looking at the instrument cluster ground. If not, then I might try to get the front end of the car as high as you can, with the car running and hot. That could help bleed any residual air. But of course be very careful in doing that!

-Darrell



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

1147cc Avatar
1147cc Silver Member Douglas Hansen
Westminster, SC, USA   USA
what thermostat do you have? have you tested it? I always drill a small hole in any new stat that doesnt have one already.

Ive always found that the temp gauge would read high just before the thermostat would open then drop as it opened and closed at the first full temps.
I could always predict when my temp gauge would read from 0 to normal on my way to work on my mk1 spit as the temp sender was after the thermostat. It would read cold then jump to N just as it opened and closed again as the cold rad coolant flushed the head etc...



Douglas Hansen
New Parts; Engine Rebuilds; Sheet Metal work and Advice.
http://www.1147cc.com

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Bergie Bob Berg
Powell, Ohio, USA   USA
I use EMP/Stewart components 180 degree thermostat #301 which has bypass holes included......helps to bleed system and keeps a small amount of coolant moving...best you can buy...if your using edelbrock,offy. or OEM manifold you can spin the tstat and have a hole on the top of housing for better bleed of air...

Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
Answers in quote below.

In reply to # 1499382 by darrellwalker Hi Patrick,

The hole is to help bleed air out of the system. Having air could contribute to what you see. But there is also a known issue when the fans come on, that if the instrument cluster isn't well grounded, that will cause a high reading. The pins in the connector at the top of the instrument cluster can loose tension, or become corroded. I cleaned the connector last spring but I will double check continuity.

Also, do you have all of the original bypass hoses in place? Is it an original water pump? Some reproductions a while back where also missing a bypass hole. Doing some investigating this morning there is no by pass hose hook up. The hose off the reservoir tank is blocked off. Looking through Rimmers catalog this morning there is a thermostat housing for 4BBl carbs that has the location for the by pass hose that my housing does not. Also I do not see a by pass hose on the water pump and I am not sure were it would be located. The thermostat I have is either a 190 or 195 Rimmers calls for 160 for all 3.5 rovers.

Anyway, if you can correlate the fluctuations to the radiator fans cycling on and off, I would start with looking at the instrument cluster ground. If not, then I might try to get the front end of the car as high as you can, with the car running and hot. That could help bleed any residual air. But of course be very careful in doing that!

-Darrell



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
In reply to # 1499452 by Pat.L I cleaned the connector last spring but I will double check continuity.

It isn't just a continuity problem, but an issue of how much current needs to pass when the fans come on.

In reply to # 1499452 by Pat.L Doing some investigating this morning there is no by pass hose hook up. The hose off the reservoir tank is blocked off. Looking through Rimmers catalog this morning there is a thermostat housing for 4BBl carbs that has the location for the by pass hose that my housing does not. Also I do not see a by pass hose on the water pump and I am not sure were it would be located. The thermostat I have is either a 190 or 195 Rimmers calls for 160 for all 3.5 rovers.

I don't know why they say 160 for all 3.5 rovers, none (at least in the US) shipped with that cold of a thermostat. Do you have the stock intake manifold?



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

Bergie Bob Berg
Powell, Ohio, USA   USA
Patrick...I would replace your thermostat to rule that out, Darrell is right on with grounding....temp gauge reads higher when ground is reduced....check and clean all grounds and use di electric grease on the contact points and bolt holes...replace ground bolts also...engine ground strap check and clean, neg ground at battery, ground under pass side in trunk hinge, under dash below glove box...make sure body contact point is clean-use sandpaper...also cleanu out bolt holes....check electric temp sender -contact and wire connection is tight and secure..if original replace it.....also make sure air is out of cooling system...

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Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
I had cleaned all grounds to bare metal, but I did not know of the one under the dash below the glove box. i was planning on changing the thermostat, the temperature sender is new, but according to Rimmers' catalog it is not the correct on for a TR8 with air. That will be changed also along with the thermostat housing to correct no by pass.


In reply to # 1499463 by Bergie Patrick...I would replace your thermostat to rule that out, Darrell is right on with grounding....temp gauge reads higher when ground is reduced....check and clean all grounds and use di electric grease on the contact points and bolt holes...replace ground bolts also...engine ground strap check and clean, neg ground at battery, ground under pass side in trunk hinge, under dash below glove box...make sure body contact point is clean-use sandpaper...also cleanu out bolt holes....check electric temp sender -contact and wire connection is tight and secure..if original replace it.....also make sure air is out of cooling system...



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
I have the stock manifold but it is not on the car. The manifold on the car is for SU carburetors.
when doing some measurements on the ZS manifold for another forum member I noticed how the stock manifold used a by-pass in conjunction with the coolant for the chokes.


In reply to # 1499460 by darrellwalker
In reply to # 1499452 by Pat.L I cleaned the connector last spring but I will double check continuity.

It isn't just a continuity problem, but an issue of how much current needs to pass when the fans come on.

In reply to # 1499452 by Pat.L Doing some investigating this morning there is no by pass hose hook up. The hose off the reservoir tank is blocked off. Looking through Rimmers catalog this morning there is a thermostat housing for 4BBl carbs that has the location for the by pass hose that my housing does not. Also I do not see a by pass hose on the water pump and I am not sure were it would be located. The thermostat I have is either a 190 or 195 Rimmers calls for 160 for all 3.5 rovers.

I don't know why they say 160 for all 3.5 rovers, none (at least in the US) shipped with that cold of a thermostat. Do you have the stock intake manifold?



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

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POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
I'm am not positive about this and actual experience is with FI and now an Edlebrock equipped manifold. However looking at my factory workshop manual a couple of carburetor cooling systems and the FI system are laid out pretty well. It looks to me that none of them have ever had their bypass cast into the thermostat housing so your's is most likely correct, however they all had a bypass pipe that comes from somewhere UNDER the front of the manifold and via a short 3/8" diameter hose connects to the waterpump right next to the distributor. The waterpump bypass may be what darrelwalker was talking about missing in some waterpumps. The special thermostat housing that RimmerBros offers for the Edelbrock manifold is needed because that manifold plumbs the by-pass through the housing mount (where the thermostat housing bolts on), rather than from under as in the the OEM. As one who had that bypass blocked off I can say that the fluctuations you have are typical of of no by-pass, and probably made worse with air in your cooling system. The small hole in the thermostat can help with that. I now have a proper by-pass and any severe fluctuations are gone.

darrellwalker Darrell Walker
Vancouver, Washington, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
In reply to # 1499587 by POW The waterpump bypass may be what darrelwalker was talking about missing in some waterpumps. The special thermostat housing that RimmerBros offers for the Edelbrock manifold is needed because that manifold plumbs the by-pass through the housing mount (where the thermostat housing bolts on), rather than from under as in the the OEM.

The missing hole in some water pumps would be what mates up to the bypass. Clay Thompson had some good pictures of it, but I think his site is gone.

The Rimmer cover is pretty pricey, TA Performance also has one. Either will probably require some customizing of the top radiator hose, as they appear to exit more upward than the stock cover.

http://www.taperformance.com/proddetail.asp?prod=TA%5F1535



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
This is what I've got, Incredibly NOT cheap though!

http://aluminumv8.com/Home/NewStuff

rbaron Avatar
rbaron Roger Baron
Fort Mill, SC, USA   USA
Peter,

The D&D website shows the thermostat cover in 45, 75, + 90 deg angles. Which is correct for the TR8?

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
75°, the stock radiator hose lines up perfectly. Here's a fair photo, post #4. - Pete

http://www.triumphexp.com/phorum/read.php?3,1471791

Pat.L Avatar
Pat.L Silver Member Patrick Ledford
New Wilmington, Pennsylvania, USA   USA
Darrell sent you a PM



Patrick
1980 TR8 DHC TPVDV8AT209637
1957 TR-3 Under restoration TS20462LO
Western Pennsylvania Triumph Association
North Coast Triumph Association
TWOA

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

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