Smoke from front carb area in crossflow 1700.

[pethier]

Preliminary info to open thread.

 

Minutes after posting a digression about tying down a Seven in a trailer, I set out to see how my car felt at speed with the "hood erected" and no doors.

 

Going up a short steep hill at neighborhood speed with the engine not fully warmed, suddenly a stream of smoke about as big around as my fist issued into the slipstream from forward/under the forward air cleaner.  No strong smell.  Switched off, made it off the street and pulled the bonnet off.  No fire, thankfully.  Could not see much.  Reached in my pocket for a penny.  Didn't have one.  Walked home and fired up my Suburban and picked up my trailer.  A friendly local recognized the car as a Caterham and was a huge help in loading.  Thanks, Nick!

 

Got the rig home.  Tomorrow I will get the Seven out of the trailer, through my garage and into my shop.  Depending on what I find, it may go right back on the road or wait for spring.

 

 

[wdb]

Fingers crossed for you. 

[IamScotticus]

Any loud BANG?

[pethier]

6 hours ago, wdb said:

Fingers crossed for you. 

Thanks!

[pethier]

5 hours ago, IamScotticus said:

Any loud BANG?

There was a bit of banging and popping as the car was warming up.  I was unsure about where the "choke" (yeah I know Webers use an "enrichment circuit" instead of an actual choke) should be set.  The car has always, for the time I was testing it in Illinois and the couple of times I have had it in Minnesota, while fully-warmed-up, had some popping on the overrun, just like my 1600 did years ago.

 

But two things:

 

There did not seem to be a bang associated with the sudden onset of smoke.

and

There did not seem to be a loss of power associated with the sudden onset of smoke.  I had keep the power on to get up the hill a bit farther to get off the road.

 

I made no attempt to restart the car, and I won't until I get it from the trailer and into my shop. 

 

Edited November 16, 2023 by pethier

[IamScotticus]

See if your air filters are burnt.

 

I had popping on my 1600.

I was running too lean or had an exhaust leak.

 

Have you ever checked the rocker/valve gaps?

[MV8]

Update? Pics? Video? Scratch and sniff? No judgment on what could be a filthy engine bay.

[pethier]

9 hours ago, MV8 said:

Update? Pics? Video? Scratch and sniff? No judgment on what could be a filthy engine bay.

That was the last warm day for we don't know how long.  I had to get some outside house stuff painted.

 

Car is in my heated shop.  Doing leaf removal now. 

 

I'll get back to the car...  I suspect a wire that goes to what I think is the oil-pressure sensor, but I need time to investigate further.  

[MV8]

Still warm here (was changing leaf spring bushes yesterday for poly). The sender has been smashed but not leaking. The wire doesn't look cooked/melty and the smoke would have been very brief with a distinct odor. It could be airflow around the bay is such that it is actually some oil on the header on the other side (maybe a small cooler leak). Could also be a cooling system circulation issue with the stat closed where the gauge says it is cold but there are hot spots, though that should continue to "smoke" for a period of time.

[pethier]

5 hours ago, MV8 said:

Still warm here (was changing leaf spring bushes yesterday for poly). The sender has been smashed but not leaking. The wire doesn't look cooked/melty and the smoke would have been very brief with a distinct odor. It could be airflow around the bay is such that it is actually some oil on the header on the other side (maybe a small cooler leak). Could also be a cooling system circulation issue with the stat closed where the gauge says it is cold but there are hot spots, though that should continue to "smoke" for a period of time.

One does wonder how the sender got whacked that hard.  This car is new to me.  Has what appears to be full records from England.  

[pethier]

Took off the nose.  Pushed the car out of the shop into the garage.  Opened the garage door.  Placed a couple of fire bottles nearby. 

 

Topped up the coolant by taking it out of the overflow bottle with a turkey-baster.  I think the coolant cap is missing the outer seal that allows the engine to pull the coolant back from the overflow bottle into the radiator.

 

Started the car and warmed it all the way up.  No hot wires.  No apparent leaks.  No smoke.  Just could not make it fail.  Drove it around the neighborhood with nose and engine cover off for a while.

 

Winter is setting in, so I may not get it on the road again.  On my winter list is sourcing a proper cap and the radiator hose from the thermostat to the radiator.  It is not leaking, but there  is some checking on the thermostat end.  No point in waiting for it to fail.

 

 

 

[pethier]

[MV8]

The caps do work better with a rubber upper ring seal at the radiator neck rim for when the center disc is pulled down on it own little spring during cool down, but many caps do not have one. Bubbling in the neck during warm up? Cooling fan ever come on? Temp indication? Bonnet and nose off generally improve cooling efficiency.

 

 

[pethier]

With the rim seal: 

The car warms up.  Coolant expands and goes to the expansion tank.  Park the car and as the coolant contracts atmospheric pressure pushes the coolant in the expansion tank up the little hose into the space above the inner cap seal, from where it drains into the radiator.  In the morning, there is coolant right up to the level of of the little hose.

 

Without the rim seal: 

The car warms up.  Coolant expands and goes to the expansion tank.  Park the car and as the coolant contracts atmospheric pressure does nothing, since the pressure in the expansion tank and in the space above the inner cap seal are the same.  In the morning, there is no coolant visible all the way down to the thermostat and probably below.

 

Basically, the coolant level in the expansion tank keeps rising.  Coolant level in engine keeps falling.

 

The way this car is designed, with the expansion tank lower than the pressure cap, the outer seal is required to keep the radiator from taking in air.

 

Many caps do not have an outer seal because they are designed for cars where the expansion area is inside the pressure zone, perhaps at the top of the radiator, or in a separate expansion tank located in the pressure area.

 

This Seven has the expansion tank located outside the pressure area and lower than the radiator cap,  Either the outer seal has fallen out of the cap, or it is the wrong cap for the car.

Edited November 22, 2023 by pethier

[pethier]

It is absolutely the wrong cap. 

 

It lacks the upper seal, so the coolant does not flow back in when cooling.  Turkey-basting from the overflow to the filler every time the car is started from cold is not normal.

 

The projection of the lower seal is too short.  It is marked as a 10-pound cap, but that is only on the car it is meant to fit, not this one.  I don't feel the push-back that this design of cap is supposed to have when the cap is installed.  The distances are both 20mm.  The projection on the cap should be more than that at the housing.

 

Does anyone know the part numbers for the correct radiator cap for a 1700 Super Sprint?

Edited November 22, 2023 by pethier

[MV8]

I won't debate semantics and will use some of your terms. The height of an expansion tank, which is part of the "pressure zone", is important if it is to be the fill point. An overflow recovery tank's height, which is what you are describing, is not a factor. They also pull from the bottom of the tank with a straw. As I said, no seal and it doesn't work very well but it will flow back to a degree, just as I can do the same by blowing across the top of a straw in a glass of water. I agree a system with an overflow recovery tank should have an outer seal to be fully effective. You didn't answer my other questions but that's ok. Moving on....

If the neck depth is 20mm/0.787", then standard, domestic caps should fit fine for depth, since they are made for 3/4" but to fit a 2-1/8 od neck (SAE "A" standard). I don't know your neck id.

'60's Austin Healey, some Mercedes, and British Fords had 1 inch deep necks with 7 lb caps. I don't think they had recovery tanks or outer seals.

 

Edit: So you may need a stant 10237 or a 10337 if you want a lever pressure release.

Edited November 22, 2023 by MV8

[pethier]

>you may need a stant 10237 or a 10337 if you want a lever pressure release.

 

Thanks!