Need help here with a diagnosis. My 1997 4runner (Hilux Surf) has been supercharged for 2 years. I put 12,000 miles on it superchaged. It has 85,000 total. 8,000 of the supercharged miles were put on before I did the complete URD kit, there was occasional light pinging prior to the URD mods.
A few days ago during my annual inspection the tech noticed that the coolant was low by 3 liters (3.2 quarts). It had occasionally been running hot when stopped at a light (almost touching the red on the gauge) but would quickly cool back down when moving, I mistakenly assumed this was a fan clutch going bad. The coolant also had a burnt smell to it. He suspects there may be a head gasket leak. He did a pressure test on the coolant system and there was no leak. There is no noticable exaust steam or coolant smell from the pipe. Engine oil appears to have no contamination. Has this happened to anyone else? I did a search and found no corrolation between supercharging and blown head gaskets on this forum although blown H gaskets seem to be a more common problem with the older 3.0 engines. Any suggestions on troubleshooting this appreciated. If I do have a slow leak am I causing damage by waiting a few weeks to do the repair?

 

a supercharger can definitely blow your headgasket if you are running too much boost.

Are you sure you dont have a coolant leak somewhere that somehow got clogged up? Do a compression and leakdown test and post u the results..those are good tests for headgasket issues.

 

I was using the stock pulley so the boost should have been within reason. The leakdown test may be the best troubleshooting option.

 

How does the oil look? If it looks milky white then you have a problem.

 

The early 5VZfe had a HG recall, did you have that done? The problem with them was mainly an external leak though so look for coolant on the outside of the block. The nice thing about an external leak is it will not damage the engine, unless of course you run low on coolant and it overheats.

 

Dale, I hate to say it but that doesn't matter anymore because the campaign was over in Nov 2004 (in North America anyway).

Fingers, when was your waterpump last replaced? That is the first thing you should check (pull off the timing cover and make sure it's not leaking.....if it is you'll see a whole bunch of pink crusty stuff all over). If it has been a while since it was replaced, then do it now. If the waterpump isn't leaking and is in good shape, then I would have the entire cooling system flushed thoroughly (be sure they do it with the thermostat removed!!!!). If you do both of those and it still is throwing coolant out the overflow tank, then you have a bad HG. BTW, mine blew the HG and I had no leaks in the cooling system or white smoke out the tailpipe (keep in mind that the leak may be small enough, as it was in my case, that only cylinder combustion pressures are enough to breach the seal, thus no white smoke). The only sign was that while driving on the highway it would begin to push coolant out of the overflow tank.

If you want to see what happened to me and what the head gasket job looks like, read on:
http://www.ultimateyota.com/index.ph...6&topic=2241.0

 

Here ya go on that recall:

http://dogandlemon.com/site/japanese...seno=RJ-0521-0

 

Thanks so far, lots to check in the next couple of days. I hope it is the waterpump vice the head gasket(s). The coolant is not going out the recovery tank (that was bone dry). The oil looks clean. I'll post what I find. thanks for the help so far....off to bed it's 11PM Japan time!

 

The coolant could easily have been getting blown out the overflow because you may have lost coolant on the highway, then when you shut the truck off, the coolant from the overflow gets sucked back into the radiator. The burnt smell on the coolant is also a bad sign. My oil was also clean and no white smoke from the tailpipe either. That just means your HG leak is very small if there is one. There is also a test for exhaust gasses in the coolant which may give you an indication as well as to whether or not the HG is the culprit. Get that timing cover off and if your lucky, you'll see pink crusty stuff everywhere around the waterpump.

 

Jamie,
Read your saga, in hindsight are you convinced there was a leak in your HG? What mechanism do you think would cause the engine to overtemp if only one cylinder has a small leak into the cooling system? I'll be pulling the cover today hoping to find a WP leak.

 

Yes, 100% positive now. You can see it right on the old head gasket itself where it was leaking. The mechanism is that the head gasket is just barely leaking which creates a check valve if you will for exhaust gasses, but is not big enough to allow coolant back into the cylinder (or it is small enough that it doesn't show anything noticeable coming out the tailpipe). When you take it out on the highway under load the pressure in the cooling system rises above 15 psi (which is the max the radiator cap will contain) and begins to force the coolant out the radiator cap, into the overflow tank and eventually onto the ground. All you need is one cylinder to barely leak and your day is done until you get it fixed.

The only part of your story which might say it wasn't a HG leak is that you see the reverse of what I did.....on the highway it cools down, but coming to a stop it creeps towards the redline. That might indicate also a bad thermostat, very low coolant level (from a leaky WP) or even a bad fan clutch as you suggested before. A HG leak will make the coolant hoses feel very hard after a short period of time on the highway so if your hoses are still pliable when you pull over to check, then you probably have some other cooling issue or perhaps a prolonged lean condition. Don't assume the HG is bad until you have checked, replaced or fixed all the other items I mentioned.

 

So were you losing coolant Jamie?

 

Bigtime, it was shooting right out the overflow tank on the highway.

 

Oh...ok, I didn't see that before. Like how much did you lose?

 

Basically on the highway the temp gauge would slowly creep towards the redline and when you let off the gas then temp would come back down towards just over halfway (this is because the cylinder pressures are much less when you let off the gas and the coolant can rush back in and cool the overheated areas). If I had pushed it I'm sure it would have eventually lost all the coolant as steam out the overflow, but it was still boiling like crazy when I shut it down.

 

Fingers Check out Dale/Mt_Goats Thread He found that your stock gauge doesnt read correctly and that when it starts to show your engine heating up your already at around 240

 

Thanks!

 

An update, looks like it is a water pump. Leak is very small but there is some tell-tale residue near the pump area on the frony of the motor. No other signs it is a head gasket (no overheating/temp fluctuations at least when full of coolant, no coolant blowoff, no contaminated oil or steam from exhaust). Not sure how long I can wait but looks like a timing belt/ water pump change is in my near future. Thanks to all for the help, particularly the timing belt change link above, which will be very usefull in the near future.