328i Serious overheating

[jac-in-a-box]

Just had to rescue son ...'95 E36 328i

Engine runs smoothly - no misfire or rough running, but temp gauge into red (overheating became evident at around 40mph)

No heater output - worked fine earlier this evening.

Viscous fan coupling free running (can stop it easily with fingers at idle with engine hot) - should have some drive?

Added 5ltrs of hot water, vented system, temp dropped to normal and attempted to drive home gently. Within 1 mile overheated again. Refilled and repeated; reached home with temp gauge in red again...loads of steam from rad vent screw when opened.

Refilled with hot water, within a couple of mins overheating again at idle.

Don't "think" it's head gasket (smooth idle and no steam from exhaust)
Oil level is fine with no water apparent in sump.

Is the viscous fan coupling so important in the cold weather - would have though steady driving in night time low temps would provide sufficient cooling air flow?

Water pump?...how do you know it's duff?

Thermostat? Renewed 5k miles ago with OEM unit. Possible it's jammed shut

Thoughts please.

Cheers

[Top pup]

Sounds like the water pump, but I don't know an easy way to test it.

[phelix]

It does sound like the impeller on the pump is not turning. If the stat was jammed you would still have heat in the car.

[Gad-Westy]

Sounds like the waterpump to me as well. You could take the thermostat out just to check its not that.

[jac-in-a-box]

Thanks for replies guys.

Just pulled it all apart. Thermostat works fine, water pump is in two pieces...resin impellor is completely detached from spindle! Easy enough replacement.

As car has just turned over 100k, do you think it's wise to change radiator too? It's one of those with a plastic expansion tank "bonded" to the core. Looks OK, but had a lot of heat and steam through it last night.

Cheers

[Gad-Westy]

I'd leave the radiator but just be vigilant for any leaks etc after you've got the pump back on. Fingers crossed for you.

[evenflow]

My old '97 2.8 Z3 did that once - it turned out to be a head gasket failure

[jac-in-a-box]

Well; all back together and water is trickling out from bottom of rad, can't see eaxactly where - but is around base of molded on expansion... tank enough to know rad is goosed

Really hoping it's not head gasket; would I be safe in assuming that if engine still runs smoothly, there's no water in the oil and no external leaks from around the head/block join, that I don't have that to look forward to?

Guess, I'll find out tomorrow.

Cheers

[Gad-Westy]

jac-in-a-box said:

Well; all back together and water is trickling out from bottom of rad, can't see eaxactly where - but is around base of molded on expansion... tank enough to know rad is goosed

Really hoping it's not head gasket; would I be safe in assuming that if engine still runs smoothly, there's no water in the oil and no external leaks from around the head/block join, that I don't have that to look forward to?

Guess, I'll find out tomorrow.

Cheers

Don't wish to tempt fate but you should be ok with the head gasket if its not displaying any of the obvious symptoms. Was the car overheating for long? Any idea what temp it reached?

No idea about the radiator. Its definitly not a hose or hose clip coming adrift is it? If it is the rad you should be able to get it refurbed if you don't want to stomach the cost of a new one.

ETA If you are worrried about HGF, I'd be inclined to put everything back together, check all seems fine, and then bung a local garage £20 to get a compression test done for peace at mind.

Edited by Gad-Westy on Wednesday 12th December 16:32

[Shropshiremike]

jac-in-a-box said:

Well; all back together and water is trickling out from bottom of rad, can't see eaxactly where - but is around base of molded on expansion... tank enough to know rad is goosed

.

Cheers

Can you look at bottom of rad and see if it has bowed down?

[jac-in-a-box]

Shropshiremike said:

jac-in-a-box said:

Well; all back together and water is trickling out from bottom of rad, can't see eaxactly where - but is around base of molded on expansion... tank enough to know rad is goosed

.

Cheers

Can you look at bottom of rad and see if it has bowed down?

Yes it is slightly bowed along the bottom of the core. The lower part of the expansion tank also looks slightly distorted ie not parallel along its length.

Leak definately not from hose connections - but difficult to see from where exactly. With engine running and not hot yet, you can see the dripping by looking thro' the kidney grills towards the bottom right hand side (looking front on)
It's definately had it - new one ought to be here tomorrow.

Hadn't run long in a hot condition - kid is pretty good and pulled off soon as he noticed. Car was refilled with hot water, so hopefully all will be well.

I don't suppose 100k and 12/13 years of life is too bad - it will be if the HG has gone though!

Thanks again folks

[RedOctober]

I had the same problem a couple of years ago on my '95 E34 525i. Sudden overheating and no hot air from the heaters. Same bloody stupid design water pump with the plastic impeller. I was on a quiet road when the temp gauge started climbing, so I stopped instantly before it got into the red zone.

Fitted a new metal impeller pump and all was well again.

Plastics seem to be the bane of modern BMW's. My E34 540i auto had an autobox valve body problem with plastic check ball valves causing delayed selection of reverse. New metal valves cured the problem.

Then there are the radiators with the plastic top and bottom tanks, and the plastic hose stubs which can fracture with age if you do up the rad hose clips too tight. Later models had thick metal insert rings to stop this happening.

Now I read of plastic inlet manifolds on modern BMW Diesels breaking up and sending bits into the engine.

I mean, what's going on here? Critical parts in the engine and drivetrain should be made of metal, not brittle plastic. The weight saving of a few hundred grammes in a 1500kg car is worthless anyway, and the cost saving is also negligible compared to the overall cost of the vehicle when new.

It's just creating problems for the 3rd or 4th owners when the cars get old and out of warranty.

Hopefully your problem will just be the radiator, and not the head gasket. Serious overheating can warp the alloy head, which blows the head gasket anyway, and requires a head skim and new head gasket, but you'd be overheating badly and blowing clouds of white smoke out the exhaust if you'd warped the head and blown the head gasket badly.

Anybody with a small-block 24 valve BMW straight-six from the early-mid 90's would be well advised to check what type of impeller they have on the water pump, and replace with a metal impeller pump as a precaution.

[phelix]

jac-in-a-box said:

Yes it is slightly bowed along the bottom of the core. The lower part of the expansion tank also looks slightly distorted ie not parallel along its length.

Had this happen on my E46 328i after about 5 years; bottom of the rad looked like a banana. Almost no leak though!

[carlosvalderrama]

If you need to do a quick check on the head gasket, start it up and give it a gentle rev. A gasket leak can show up with the radiator top hose going hard under the pressurising of the coolant by the combustion gas.

it's more obvious with the thermostat open, so put some gloves on as the hose will be hot!

[Shropshiremike]

carlosvalderrama said:

If you need to do a quick check on the head gasket, start it up and give it a gentle rev. A gasket leak can show up with the radiator top hose going hard under the pressurising of the coolant by the combustion gas.

it's more obvious with the thermostat open, so put some gloves on as the hose will be hot!

If the rad has bowed at the bottom it's a good sign of excess pressure in the cooling system

Get an exhaust gas sniffer and hold it in the air void right above the water level in the expansion tank - gently rev it and watch for any HC reading rise

[8Tech]

I have seen this a few times before, check the rad cap and seal because if these let by or leak, its runs down the inside of the space between the header tank and rad and REALLY looks like a rad leak. Got caught out on this before.

[jac-in-a-box]

8Tech; can relate to your comment! Thought replacement rad was leaking the same as the "duff" one. Found coolant running down inside of black cover over exp'n tank...should've tightened the vent screw properly!
Anyway, original rad' was quite distorted so the money spent on replacement is providing a comforting blanket of security.

System venting is far from easy. After an hour of faffing around, still no hot air from heater - had to disconnect hose's from heater matrix, fill unit and hoses and was eventually rewarded with hot air. This was despite having the front of car jacked up in the air.

I didn't realise that puumps were available with metal impellors? My replacement (Valeo) has a resin impellor, as did the alternative Firstline units. Who supplies metal pumps?

Anyway all appears well now. Rock steady coolant temp and plentiful hot air - guess I should consider myself fortunate not be looking at HG failure!

Thanks to all for your comments and advice - really appreciated

[8Tech]

Metal impellor pumps from the aftermarket such as German, Swedish and French car parts or most large motor factors.