Loss of coolant and head gaskets ......

[bob12]

Huummm .... 1990 745 B200F LH2.4, 150k miles, etc.

.... I seem to be loosing coolant. Currently I don't think quickly, but it's going down! There also seems to be a popping noise (say every 5/10 seconds or so) from somewhere low'ish near the backend of the engine in the general area of the exhaust manifold downpipe to the cat. (oh dear, and makes me think of water in the exhaust!)

I have thoroughly checked the cooling system/hoses and I am currently satisfied there is no sign of a visible leak. Nor, is there any sign of oil in the coolant, but, (and it's now dark so investigation has has ended for the day) and maybe with hindsight, I saw the coolant level in the header tank fluctuating in time with the engine speed when I revved the engine.

Consequently, I am wondering if the head gasket is on its way out and water is getting into a cylinder.

Any thought/comments welcome.

Bob

[stephend]

Let it cool down completely overnight. First thing in the morning, crack open the pressure cap on the header tank. If there's pressure in there, then it's likely that the HG is starting to let go.

To be sure, get your friendly local MoT man to use his emissions probe to 'sniff' the air just above the coolant. If it registers exhaust gases, that's a smoking gun (so to speak!).

By the way, HG leaks can do funny things to coolant levels. The HG went on my Toyota, and caused the level in the header tank to go up, not down!

[bob12]

Originally Posted by stephend

Let it cool down completely overnight. First thing in the morning, crack open the pressure cap on the header tank. If there's pressure in there, then it's likely that the HG is starting to let go.

To be sure, get your friendly local MoT man to use his emissions probe to 'sniff' the air just above the coolant. If it registers exhaust gases, that's a smoking gun .....

Thanks Stephend ... I will have to give it a drive as I have already opened the header to top it up. If I still have problems I will call my mechanic on Monday as I am sure he's got a gas sniffer.

Very annoyingly, I have had various minor niggles with the car since the New Year. I only went to my mechanic today because I had a whining noise in time with the engine revs and was convinced it was either the new water pump or the tensioner roller that was fitted in mid-Jan, but oh no, it was clearly the alternator when a wonderful set of headphones and stethoscope thingy was put near suspects!! To which he said with a smirk .. "that's OK you have a spare one of those" !!

Maybe it's time to sell after 28+ years, although I did spend some hours cleaning and polishing it today!

Bob

[stephend]

Lol!

Seriously, though, a head gasket change is straightforward on a red-block: I did mine myself, and I'd never done anything like that before.

[aardvarkash10]

All the usual suspects:

Check for wet floor, right-hand side footwell. If its wet, sticky and smells sweet, its probably a leaking heater matrix or heater control valve (non-aircon car). Both are horrid replacement jobs.

Check the radiator end tanks. The fibre-reinforced ones develop fine crack lines that bleed and will leave a colour line the same colour as the coolant. They can also start to leak where the tanks are joined to the core. No fix but to replace it unfortunately.

If you suspect head gasket, just do a gas test or HC test on the coolant. Any worthwhile workshop will be able to do this for you. It will detect a change in chemistry in the coolant and/or they may do a check for exhaust gases in the coolant. Either way it will pick up a problem before the physical evidence (rapidly changing and surging coolant levels) become obvious.

[bob12]

Originally Posted by stephend

Lol!

Seriously, though, a head gasket change is straightforward on a red-block: I did mine myself, and I'd never done anything like that before.

Yea .. done several head gaskets in my lifetime, BUT do I want to be arsed to do it myself now

[bob12]

Originally Posted by aardvarkash10

All the usual suspects:

Check for ........

If you suspect head gasket, just do a gas test or HC test on the coolant. Any worthwhile workshop will be able to do this for you. It will detect a change in chemistry in the coolant and/or they may do a check for exhaust gases in the coolant. Either way it will pick up a problem before the physical evidence (rapidly changing and surging coolant levels) become obvious.

Thanks - as said done all usual suspect checks including carpets, and will now wait and see what happens tomorrow, but reckon next stop may well be a coolant HC check if I am still twitching.

[stephend]

Originally Posted by bob12

Yea .. done several head gaskets in my lifetime, BUT do I want to be arsed to do it myself now

Ah, but even at garage rates, if it buys you another 28 years, I'd say it's not a bad investment.

[Laird Scooby]

What coolant are you running in the engine Bob?

[bob12]

Originally Posted by Laird Scooby

What coolant are you running in the engine Bob?

Well ... I am not really sure as I had a new water pump and cambelt/tensioner fitted in mid- Jan this year when the top 'O' ring on the pump let go. However for many years now I have used Comma Xstream G48 and have topped it up with that a couple of times recently. The existing was also the same bluey colour, and I have never had a problem with whatever my mechanic puts in.

I topped it up yesterday evening and put a mark on the header tank. The water level has gone down about 1 mm but that maybe due to cooling overnight.

The car has been as good as gold all its life and never really used or lost water ... until now!

I didn't mention it earlier but also there's no water in the oil.

I had been using the car yesterday morning and had been to see my mechanic who confirmed a whistling noise I was now hearing in time with the revs is the alternator on their way out (that's OK I have a spare!!).

In the afternoon when I moved the car I noticed a puddle of something on the ground to the back of where the engine would have been. I sniffed it but it didn't really smell of anything and when I put a hose on it to see if it was oil from the power steering there didn't seem to be any oil in it. Maybe there's a problem around the back end where the hoses go through the firewall that I haven't spotted (a few years ago the back heater hose blew so that should be OK).

When it's stopped raining I shall continue to have a poke around, and also take the top half of the cambelt cover off just to doubly check that there is no leak from the pump (there is none visible or on the engine under trays, but that won't be until Monday.

Any idea what the popping noise might be. I put it down to a slight blow in the exhaust?

One always assumes the worst when these things happen (well at least I do!!).

Cheers, Bob.