Overheating at high speeds

[70herald]

Ok, kind of weird problem. The herald seems to be overheating at highway speeds. Around town, stop and go traffic it is doing alright.

As far as temperatures, the engine is no boiling over, but it runs much higher on the highway than at low speeds, (I measured the temperature at 90C)

Clearly it is not a problem of lack of airflow considering I was driving at nearly 70mph, engine is properly tuned, dizzy just came back from Jeff at Advanced Distributors and is set at 13degrees BTC w/o vac, and the fuel mixture is a bit rich. Radiator was taken apart, cleaned and declared to be in good shape a few months ago.

On the Canley site they mention the following:
"One very rare problem we encounter on cars that continue to overheat when all else has been checked or renewed is corrosion in the void in the water pump housing where the pump impeller usually fits. Very slight erosion here can have a drastic affect on the efficiency of the water pump. Substitution with a better S/H housing is the only answer."

Any thought or other ideas? I am not real anxious to ship a block of cast iron air-mail if it isn't going to help.

 

[toysrrus]

What about your Thermostat?

They are typ. avail. in a couple of heat ranges. Perhaps that could be a problem?

In any case; Its an "Easy & In-Expensive" as well as necessary change or fix.

Strange occurance Indeed!!

Russ

 

[myspitfire]

Hello;Are you getting the high temps at the dash guage?(voltage stabilizer?)(or maybe the temp sender?)If these two items are questionable i'd replace them anyway.Then look at your problem.Purchase a can of "RED-LINE WATERWETTER",that alone will give you(abit) better flow.
Ken&Whitelightning

 

[70herald]

Thermostat is new, temp sensor is new, the voltage regulator is electronic, and the gauge reading is fairly stable until I start driving on the highway. I double checked the engine temperatures with an electronic thermometer to double check. For the most part, driving around the engine (on the head) was close to 70C, which is good since I have a 68C thermostat. After driving on the highway, measuring in the same place I was around 90C or even a bit more. Water wetter may help, but I have no local source.

 

[14dna]

Yisreal;
Have you changed out the hoses?
I have seen them collapse at speed and cut off circulation.
Just a thought.

Dave

 

[Banjo]

The water pump may not be circulating coolant very well, or like others have said, somthing else is restricting coolant flow. Possible that the "new "thermostat is not opening far enough.

 

[NutmegCT]

Couple things I remember reading about TR engine overheating - may not all apply to your Herald:

Correct (sleeved?) thermostat? Evidently some don't have the sleeve, and hot coolant can "backflow" into the engine.

Fan blades bent and actually "blocking" air at high speed.

Radiator has proper flow throughout the grid? Crud and/or dents causing circulation snarl ups?

Carb(s) not too lean?

Proper radiator cap - some have a slightly shorter neck than spec, and don't reach the bottom to correctly seal.

Coolant flow blocked in the engine? If you open the drain cock on the side of the block, is there a good flow of coolant out the opening?

Check head bolt torque. Might be a very small leak in/past the gasket allowing combustion gasses to super heat the coolant.

Hope this helps.
Tom

 

[swift6]

What kind of RPM are you turning at highway speed. Could the pump be cavitating? Could be part of that erosion equation. Does anything have a smaller pulley making the water pump spin faster like say the alternator/generator?

 

[Opa]

proper pressure cap installed?

 

[70herald]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Have you changed out the hoses?[/QUOTE]
New
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The water pump may not be circulating coolant very well, or like others have said, somthing else is restricting coolant flow. Possible that the "new "thermostat is not opening far enough.
[/QUOTE]
I think I will have to take it the pump /housing / thermostat all apart. I did get the thermostat from a reputable Triumph specialist but who knows. It is NOT the sleeved type but then there isn't a bypass on these pumps like on the old TRs so that shouldn't mater but then it may not be opening enough.



<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Carb(s) not too lean?[/QUOTE]
I think that the carb is actually slightly rich, at idle it is very rich.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Proper radiator cap - some have a slightly shorter neck than spec, and don't reach the bottom to correctly seal.[/QUOTE]
seals properly and I am not getting boil over (yet)

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Coolant flow blocked in the engine? If you open the drain cock on the side of the block, is there a good flow of coolant out the opening?[/QUOTE]
Yep, I spent hours cleaning out the block when it was rebuilt last year.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Check head bolt torque. Might be a very small leak in/past the gasket allowing combustion gasses to super heat the coolant.[/QUOTE]

This is an interesting idea, but where are the gases going, in any case, I am aproaching ~500 miles since the rebuild so it is time to tighten the head.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]What kind of RPM are you turning at highway speed. Could the pump be cavitating? Could be part of that erosion equation. Does anything have a smaller pulley making the water pump spin faster like say the alternator/generator?[/QUOTE]

Well I was keeping up with traffic and with a 1:4.11 backend, the engine was going at a good clip. I guess 4500RPM or more. Could be. The pump and crank pulleys are stock size.


<div class="ubbcode-block"><div class="ubbcode-header">Quote:]proper pressure cap installed?[/QUOTE]
Yep 13 PSI, I am NOT boiling over but it is above the temp that it should be at.

 

[philman]

I had an old toyota that only ran hot at highway speeds, and really never overheated. it turned out to be the head gasket -- after replacing everything else I figured why not -- I never figured out why, unless maybe the head was slightly warped. I had it resurfaced when I replaced what looked like a perfectly good head gasket.

 

[Opa]

with only 500 miles on a new engine she may loosen up some with more miles driven. I know my 6 run fairly hot for the first while after rebuild until i put some more miles on and went to synthetic oil. At 4500 rpm continuous, things are getting fair busy inside the block,especially on a fresh engine.

 

[Geo Hahn]

with only 500 miles on a new engine she may loosen up some with more miles driven...

In my experience a rebuilt can be pretty tight for a couple of thousand miles causing somewhat higher temps.

 

[tomshobby]

Like others have said, it really sounds like a coolant flow problem.

Recent fixes are radiator and thermostat.

Is there some restriction in either? Maybe a gasket or some other foriegn material in the system that is partially blocking flow. I once installed a good radiator after it had sat for a while. The car just did not cool. After some other kind of heat I found a squirl had stored nuts in the top tank.

Is the vent hole in the thermostat blocked?

A hose that might be collapsing when the pump turns faster?

Excessive clearence between the pump vanes and the inside of the housing? Should only be about .035 to prevent cavitation.

Is the exhaust blocked? Might have been crushed by a jack.

Have you tried different timing settings?

May be valve timing or adjustment.

Or, none of the above.

 

[70herald]

Ok, I took the water pump off today. It doesn't look to bad inside. The thin ring of iron which comes close to the pump blades is nearly perfect.
There is a hole between the front and back parts of the pump, it looks like someone drilled in a bit to far when they drilled the holes for the studs. I might fill that in with a bit of epoxy, but I doubt that that will make any real difference. I also squirted water through the head, and it flowed nicely.

The thermostat doesn't have a vent hole, I could easily drill one in.

The exhaust isn't crushed, but I do seem to have a fair amount of pressure building up. Under full load, I do have a bit of gas escaping from the manifold / exhaust pipe connection. Maybe something is plugged up in the exhaust. I could hack off the muffler and see what happens. (other than the neighbors complaining)

Also do to a problem with old studs I had to pull off the head and replace it so there could well be a problem with the head gasket so I guess the head should come off. Uck, I was really hoping to drive a bit.
Yisrael

 

[RonMacPherson]

Do you have a vacuum gauge?

A quick way to determine if you have exhaust restriction is to install the vacuum gauge and go for a road test. As the throttle is opened manifold vacuum will decrease(On the triumphs should start at minimum 17 psi) when you go full throttle should drop to 0. At a cruise should hold a fairly steady pressure reading of appx 12-13 depends on the cam and ignition timing. some may go as low as 9, but you are looking for a steady reading.

If the reading stabilizes and then drops(or raises, forget which) under a steady pedal pressure then you have a restriction.

You should be able to search engine(google?) how to use a vacuum gauge and it should pull up the definites.

 

[tomshobby]

Yisrael, sure hope you find it. Probably be somethine one of those "why didn't I see this before" things.

 

[70herald]

I don't have a vacuum gauge, but I should be able to get a hold of one. I guess that that will be one of those things that will have to be on my list of stuff to look for.

 

[NickMorgan]

My friend's Vitesse has a 2.5 litre injected engine and its cooling is marginal at high speed, yet fine when it is going slower. I suspect that, as the cars were designed before motorways were common, they will struggle to keep cool at 70mph, especially when the air temperature is more than expected in England!

 

[Roger]

90°C isn't wildly too hot for a newish engine, in my viwe. I certainly wouldn't start taking the head off or anything dramatic until other possibilities have been exhausted.