These bubbles normal?

[ElanBRG]

I bought Otis' BRG 91 Elan on Bring a Trailer, and I am going through it right now to assess the car's overall condition.

Can someone tell me if this level of bubbling from the small return line in the coolant reservoir is normal when the thermostat opens? Apologies in advance for the orientation of the video.

http://www.youtube.com/watch?v=lZU_AJPTa8s

I just used a coolant block tester (blue dye that turns yellow if there are exhaust gases in the cooling system), and it stayed the same color of blue throughout. Once the car gets warm enough for the thermostat to open up though, it's impossible to use the tester for very long because the coolant flow in that header tank is pretty violent with a lot of sloshing and then quickly rising in level.

There is no milky residue on the oil filler cap, and everything looks good through the oil filler cap hole.

There is a little dribbling of oil around the front of the engine near the head gasket area, but it's pretty minor and when I wiped the oil away, it's taking a while to come back.

I am going to do a compression test later this weekend, and also vacuum test the cooling system. Unfortunately, my cooling system pressure tester doesn't fit this car, so I will need to buy another kit online because the ones I can rent at the auto part stores also don't have the right size.

Thanks!

[John_W]

Oil dribble on the right of the engine (as you look at it with the bonnet open) is likely just a CAS ”O” ring needed, plus one for the blanking plug while you’re there. Takes maybe an hour and a couple of quid for the nitrile O-rings. Not serious.

Water bubbling is another matter and sounds more serious. I’ll leave it to others to comment, but at worst it’s a head gasket which is a weekend DIY job if you’re up for it.

John

[Giniw]

John, do you happen to know what size is the CAS o-ring? I suspect I need a new one.

[ElanBRG]

Oil dribble on the right of the engine (as you look at it with the bonnet open) is likely just a CAS ”O” ring needed, plus one for the blanking plug while you’re there. Takes maybe an hour and a couple of quid for the nitrile O-rings. Not serious.

Water bubbling is another matter and sounds more serious. I’ll leave it to others to comment, but at worst it’s a head gasket which is a weekend DIY job if you’re up for it.

John

Thanks for the info on the CAS O-ring and blanking plug. I will definitely tackle those items.

[John_W]

Giniw,
sorry, no straight answer, unless you believe Geoff, in which case it’s 23.7mm (ID) x 3.5mm.
See here and here.

If that doesn’t help I can go digging in my spares box!

John

[ElanBRG]

Well, I am really starting to think those bubbles are nothing to be concerned about.

I just repeated the exhaust gas test, and no signs of any exhaust gases at all after a long time of sniffing. It says 2 mins, and I went well beyond that. The tester was pulling a good vacuum on the header tank which is further evidence that exhaust gasses aren't getting into the cooling system, otherwise they would be pushing the tester out.

That, and the fact that the car is not overheating, it runs very smoothly, and the minor oil leak does look like seals John mentioned after reevaluating the oil residue under the CAS.

It's hard to see any of the markings on the coolant reservoir, but now I see it was overfilled to the very top. I dropped the level to the cold setting, while cold, and there no longer any signs of concerning bubbles. It was probably just picking up a little bit of the air at the top of the coolant reservoir as the hot coolant came out of that return line.

[John_W]

The level of the coolant when cold should be about half way up the clear(ish) plastic expansion tank, about the level of the seam. Certainly not filled to the top!

Beware of coolant overflowing onto the coils and mounting plate electronics which sit (conveniently) under the expansion tank. That gets you into another load of trouble.

[ElanBRG]

The level of the coolant when cold should be about half way up the clear(ish) plastic expansion tank, about the level of the seam. Certainly not filled to the top!

Beware of coolant overflowing onto the coils and mounting plate electronics which sit (conveniently) under the expansion tank. That gets you into another load of trouble.

Good to know! Would be nice if they had an overflow tank instead of just spewing excess out the cap right there. I am sure someone here has added one at some point.

[lotusflasherman]

Having watched your video I'm wondering if the thermostat is the problem. The thermostat sits vertically and the correct thermostat has a 'jiggle pin valve' that should be fitted uppermost (@ 12 o'clock) so air doesn't get trapped behind it in the thermostat housing. If your 'stat hasn't a jiggle pin or it's not @ 12 o'clock that might cause the bubbles.

Posted a link here about testing the pressure cap with a tyre pump ... brief instructions and a youtube video ...lotuselancentral.com topic

[Simon_P]

There is no point in having an overflow tank - it is supposed to be a closed system.

Check the handbook for the fill level. Kalt means cold in German. And cold means properly cold.

When it's cold bleed the system. The screw is under the headlamp pod. Release the filler cap first to allow air out rather than pulling it in. Make sure that the cap is tight.

As Phil says check that the thermostat is working correctly - opens at 1/4, stays at 1/4 while driving and that the fans come on at 3/4

Is the tick over speed 950 rpm? It sounds higher in the video.

[ElanBRG]

Having watched your video I'm wondering if the thermostat is the problem. The thermostat sits vertically and the correct thermostat has a 'jiggle pin valve' that should be fitted uppermost (@ 12 o'clock) so air doesn't get trapped behind it in the thermostat housing. If your 'stat hasn't a jiggle pin or it's not @ 12 o'clock that might cause the bubbles.

Posted a link here about testing the pressure cap with a tyre pump ... brief instructions and a youtube video ...lotuselancentral.com topic

I bought a new thermostat as part of the stuff to change when I do the timing belt. Bought a Gates 33478S from Rock Auto, so hopefully that's the right one. It does have the jiggle pin.

[Simon_P]

The stat should be excentric ie not in the middle

[ElanBRG]

The stat should be excentric ie not in the middle

Ok, thanks, this gates thermostat is definitely not centered.

[Brit-Car-Nut]

When it's cold bleed the system. The screw is under the headlamp pod. Release the filler cap first to allow air out rather than pulling it in. Make sure that the cap is tight.

As Phil says check that the thermostat is working correctly - opens at 1/4, stays at 1/4 while driving and that the fans come on at 3/4

Is the tick over speed 950 rpm? It sounds higher in the video.

The US/FED car does NOT have a bleed screw since the radiator is mounted differently from the UK/ROW cars.

The thermostat purchased is correct for the Isuzu engine.

[Simon_P]

Just watched your video again.

... I thought I would point out that the mark for Kalt is clearly visible below the seam.

[Brit-Car-Nut]

The thermostat sits vertically and the correct thermostat has a 'jiggle pin valve' that should be fitted uppermost (@ 12 o'clock) so air doesn't get trapped behind it in the thermostat housing. If your 'stat hasn't a jiggle pin or it's not @ 12 o'clock that might cause the bubbles.

Positioning the thermostat in this position assures the "opening component" (wax bulb) is fully immersed in the coolant so it opens and closes correctly.

[ElanBRG]

The thermostat sits vertically and the correct thermostat has a 'jiggle pin valve' that should be fitted uppermost (@ 12 o'clock) so air doesn't get trapped behind it in the thermostat housing. If your 'stat hasn't a jiggle pin or it's not @ 12 o'clock that might cause the bubbles.

Positioning the thermostat in this position assures the "opening component" (wax bulb) is fully immersed in the coolant so it opens and closes correctly.

That doesn't make sense to me. There is a header tank full of water suspended well above the thermostat housing, and there is an air bleed line from the top of the thermostat to the header tank that is going to bleed out any air initially in the system to the top of the header tank. After the initial automatic bleeding after a refill, there should never be any air circulating in the engine/thermostat, so the thermostat should always be fully submersed in coolant regardless of the orientation of the thermostat. Trapped air in an engine is a very bad thing, and not something fixed by making an off-center thermostat.

[Brit-Car-Nut]

The thermostat "gate" is not in the center of the thermostat. It is offset. That way the thermostat needs to be installed in a specific direction so the bleed hole is at the top and the "gate" portion is at the bottom and more deeply immersed in the coolant. The jiggle pin is there to help purge the system and prevent pressure pockets.

[ElanBRG]

The thermostat "gate" is not in the center of the thermostat. It is offset. That way the thermostat needs to be installed in a specific direction so the bleed hole is at the top and the "gate" portion is at the bottom and more deeply immersed in the coolant. The jiggle pin is there to help purge the system and prevent pressure pockets.

If the whole thermostat is immersed in coolant, how can it be "more deeply immersed?" Not saying the jiggle pin shouldn't be at the top, but lots of thermostats that are centered have giggle pins, so that doesn't explain the need for the offset gate. If the giggle pin is doing it's job to bleed the air out, then there is no more air circulating after the initial bleed. And if more air is entering the coolant, you have something wrong with your engine that needs to be fixed, not compensated by an offset gate and a giggle pin.

[Brit-Car-Nut]

The cavity is NEVER full. The engine has larger flow areas and a thermostat will not work if it not completely immersed.

A "normal" thermostat would be around 30% out of the flow once the thermostat opened and allowed the coolant to circulate.

There is a lot more science to the cooling system beside running coolant through the engine. It has to flow at a rate where it will "pick up" the heat and carry it to the radiator to exchange it. That is why race engines never run without a thermostat or a blanking sleeve. The coolant never collects the heat and the engine will overheat but the sensor for the gauge won't know it because the coolant never got to do it's job.

Put it together however you want. You could try reading the service manual. Lotus (and Isuzu) apparently wasted the extra sentence to clarify the position and direction of the thermostat fitment.